Detection of E. coli O157:H7 using bacterial molecularly imprinted bipolar electrode and Au@metal-organic framework

Detection of E. coli O157:H7 using bacterial molecularly imprinted bipolar electrode and Au@metal-organic framework | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Detection of E. coli O157:H7 using bacterial molecularly imprinted bipolar electrode and Au@metal-organic framework Yunlong Liu, Panpan Liu, Mengjuan Li, Fengyang Wang, Yusong Wan, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7210225/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract A bacterial molecularly imprinted bipolar electrode (BPE) sensor combined with Au@metal-organic frame (Au@MOF) was developed for the E. coli O157:H7 detection. Firstly, dopamine (DA) was mixed with E. coli O157:H7 through an electropolymerization process to form polymer film on the BPE cathode. After bacteria removal, the bacterial molecularly imprinted polydopamine (PDA) film remained on the cathode, exhibiting high specificity for bacterial recognition and binding. Secondly, the E. coli O157:H7 aptamer was modified to the Au@MOF surface by Au-SH covalent bonds. Then, E. coli O157:H7 was present at the cathode, through the specific binding of aptamer to E. coli O157:H7, Au@MOF was assembled to the electrode surface. Finally, 3,3′,5,5′-tetramethylbenzidine/H2O2 (TMB/H2O2) solution was added to the cathode. The Au@MOF exhibited peroxidase-like activity and could catalyze the reduction reaction of TMB/H2O2 system. Due to the electrical neutrality principle of the BPE, the oxidation reaction of [Ru(bpy)3]2+/tripropylamine ([Ru(bpy)3]2+/TPA) system on the anode, generating a distinct Electrochemiluminescence (ECL) signal. The sensor detected E. coli O157:H7 within a concentration range of 1 to 106 CFU mL-1, with a detection limit of 1 CFU mL-1, demonstrating high selectivity and sensitivity. This BPE platform, integrating molecular imprinting and Au@MOF-assisted oxygen reduction, shows significant potential for bacteria detection in various applications. BPE-ECL Metal-Organic Frameworks Bacterial Molecularly Imprint Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Food safety issues significantly impact public health and represent a critical concern that warrants immediate attention. These issues are intricately linked to human health and have profound consequences on economic and social development [ 1 ]. The causes of foodborne diseases are diverse and multifactorial, involving bacteria, fungi, viruses, parasites, and chemical contaminants present in food. Among these, foodborne pathogens are the predominant contributors to such diseases [ 2 ]. As environmental pollution intensifies, pathogens can rapidly proliferate and spread, exacerbating health-related issues. Consequently, it is imperative to develop rapid and sensitive bacterial detection methods for early clinical diagnosis [ 3 ][ 4 ]. Although traditional culture-based detection methods are reliable, they are often cumbersome, time-consuming, and limited in sensitivity. In contrast, non-culture detection technologies, such as mass spectrometry, colloidal gold assays, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assays (ELISA), offer improved sensitivity and reduced analysis time [ 5 ]. However, these techniques still face challenges, including complex sample preparation, high costs, and the need for skilled personnel [ 6 ][ 7 ][ 8 ]. Electrochemiluminescence (ECL) is an effective biosensing technology known for its high sensitivity, strong selectivity, good controllability, and ease of operation [ 9 ]. The recognition element is a critical component, significantly influencing both selectivity and sensitivity. One reported amplification strategy involves utilizing nanomaterials as electrochemical modifiers to enhance the detected ECL signal [ 10 ]. Metal-organic frameworks (MOFs), which are porous materials with a crystalline structure, are advanced materials formed from metal ions/clusters and organic ligands through coordination reactions. These frameworks can form three-dimensional structures with distinctive properties that promote substrate diffusion. MOFs typically feature active components, functionalized pore surfaces, high surface-to-volume ratios, and large pore volumes [ 11 ][ 12 ]. MOF-modified electrodes containing electroactive substances can significantly improve electrode conductivity, thereby enhancing sensor sensitivity. Gupta et al. [ 13 ] developed an electrochemical sensor based on an iron-based MOF (MIL-53) for detecting Escherichia coli ( E. coli ). They combined polystyrene sulfonate (PEDOT: PSS) with MIL-53 to introduce electrochemical activity and optimized the encapsulation amount of PEDOT: PSS within the MOF pores to achieve optimal conductivity. The composite material, due to its specific antibodies against E. coli, was used to modify screen-printed electrodes (SPE). By employing differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS), E. coli was detected across a wide concentration range of 2.1 × 10 2 to 2.1 × 10 8 CFU mL − 1 , with a detection limit of 4.0 CFU mL − 1 . Molecularly imprinted polymers (MIPs) are rigid structures formed by the copolymerization of functional and crosslinking monomers in the presence of a molecular template. This templated synthesis enables the self-organization of functional monomers around the template, while the crosslinking monomer solidifies their positions into a rigid matrix. Once the template is removed, cavities are formed within the MIP, exhibiting complementary characteristics in size, spatial shape, and the distribution of chemical functional groups relative to the target molecule. These features confer high-affinity and selective binding sites for the template [ 14 ]. Electropolymerization is the process of electrolysis conducted in an electrolytic cell containing an appropriate electrolyte, using specific electrochemical methods. During this process, monomers on the electrode surface undergo oxidation, reduction, or decomposition, generating intermediates such as free radicals or ions, which initiate polymerization reactions. Electropolymerization is a powerful tool for generating uniform films on electrodes and allows easy adjustment of film thickness by varying the number of deposition cycles [ 15 ]. However, a limitation of this technique is the restricted range of monomers that can undergo electropolymerization, which limits the possibilities for MIP synthesis. Reports suggest that dopamine, as an electropolymerizable monomer, can interact with various templates through non-covalent interactions such as π-π stacking, electrostatic interactions, and hydrogen bonding [ 16 ]. Polydopamine (PDA) is a biomimetic polymer first identified in 2007 [ 17 ]. Inspired by the adhesive proteins found in marine mussels, which are rich in dopamine (DA) and lysine, early studies revealed that DA undergoes self-oxidation to dopamine-quinone, which subsequently cyclizes to form 5,6-dihydroxyindole (DHI), a critical precursor to PDA. Additionally, the amine and catechol functional groups of polydopamine promote metal-ion coordination [ 18 ]. For instance, Yang et al. developed PDA-coated nanocomposites that feature a MOF shell encasing a nanoparticle core [ 18 ]. This study developed a bipolar electrode (BPE) sensor by integrating Au@MOF with bacterial molecularly imprint for the detection of E. coli O157:H7. As illustrated in Fig. 1 , bacterial molecularly imprint provides selective cavity adsorption of E. coli O157:H7, while Au@MOF facilitating redox reactions. By introducing SH-Apt, Au@MOF was effectively immobilized onto the cathodic end of BPE. The subsequent addition of 3,3′,5,5′-tetramethylbenzidine (TMB), a redox-active substrate, further amplified the ECL signal. The resulting sensor exhibited high sensitivity and specificity for E. coli O157:H7, demonstrating considerable potential for practical applications. 2. Experimental part 2.1. Materials and apparatus E. coli O157:H7 (CICC 10907), Salmonella typhimurium ( S. typhimurium , ATCC 14028) and Staphylococcus aureus ( S. aureus , ATCC 29213) came from Guangdong Microbial Culture and Collection Center (GDMCC). Ternary pyridine hexahydrate ruthenium chloride (Ru(bpy) 3 Cl 2 .6H 2 O) and tripropylamine (TPA) were acquired from Sigma-Aldrich Ltd. (St. Louis, Missouri, USA). LB broth (CICC10907) was obtained from Qingdao Haibo Biotechnology Co., Ltd. (Qingdao China). H 2 O 2 , HAuCl 4 , terephthalic acid (H 2 BDC), FeCl 3 ·6H 2 O, ethanol, dopamine (DA), 3,3',5,5'-tetramethylbenzidine (TMB) and anhydrous sodium acetate were procured from Nanjing Wanqing Chemical Glassware & Instrument Co., Ltd. (Nanjing China). Sodium citrate was procured from Tianjin Xiansi Aopude Technology Co., Ltd. (Tianjin China). Sodium dodecyl sulfate (SDS) was procured from Shanghai Macklin Biochemical Technology Co., Ltd. (Shanghai China). N, N-Dimethylformamide (DMF) was procured from Shanghai Meirui Biochemical Technology Co., Ltd. (Shanghai China). Thiolated aptamer for E. coli O157:H7 (SH-Apt): 5′-SH-TGA GCC CAA GCC CTG GTA TGC GGA TAA CGA GGT ATT CAC GAC TGG TCG TCA GGT ATG GTT GGC AGG TCT ACT TTG GGA TC-3′ was synthesized by Sangon Biotech Co., Ltd. (Shanghai, China). The following buffer solutions were used in this study: PBS (pH 7.2–7.4, containing 136.89 mM sodium chloride, 2.67 mM potassium chloride, 8.24 mM disodium hydrogen phosphate, and 1.76 mM sodium dihydrogen phosphate); ECL detection solution (PBS with 50 mM [Ru(bpy) 3 ] 2+ and 250 mM TPA, prepared fresh daily); dopamine electropolymerization buffer solution (1×PBS containing 3 mM dopamine, pH 6.5, deoxygenated with nitrogen gas for 15 min); and TMB/H 2 O 2 solution (1 mL total volume, comprising 890 µL sodium acetate, 100 µL of 10 mM TMB, and 10 µL of 10 mM H 2 O 2 ). All buffers were prepared using an ultra-pure water system (GWA-UN1-F40, Persee, China) with a specific resistance of 18.2 MΩ·cm − 1 . In this experiment, all electrochemical measurements were conducted using a CHI750E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd., China). The ECL signal of [Ru(bpy) 3 ] 2+ (λ max , em = 620 nm) was detected with a fluorescence spectrophotometer (Fmur4700, Hitachi, Japan), operating at a scanning speed of 12,000 nm/min, in strict accordance with the parameters established in our previous work [ 19 ]. The microstructural morphology and elemental distribution during the synthesis of MOF, Au@MOF, and BPE cathodes were systematically characterized using scanning electron microscopy (SEM; ZEISS Sigma 360 1) and energy-dispersive X-ray spectroscopy (EDS; Ultim Max 65). UV-vis spectra were obtained by a Rayleigh UV-1601 spectrophotometer (Beifen-Ruili Analytical Instrument Company. Limited, China). 2.2. Bacteria culture E. coli O157:H7 was inoculated into Luria-Bertani (LB) medium and incubated at 37°C for 18–24 h with shaking at 160 rpm. The bacterial suspension was washed, resuspended to a concentration of 10 8 CFU mL − 1 , and then serially diluted tenfold to achieve the desired concentration. 2.3. Preparation of Apt-Au@MOF The MOF was synthesized via a hydrothermal method [ 5 ]. Specifically, 0.126 g of H 2 BDC and 0.187 g of FeCl 3 ·6H 2 O were dissolved in 15 mL of DMF. Subsequently, 1.67 mL of acetic acid was added, and the mixture was stirred until complete dissolution. The homogeneous solution was then transferred to a preheated oil bath and stirred at 120°C for 4 h. Upon completion of the reaction, the solution was cooled to room temperature naturally. The product was isolated via centrifugation and washed sequentially with DMF, ethanol, and deionized water to remove residual reactants. The resulting precipitate was collected and stored in deionized water. A 5 mL MOF solution (1 mg mL − 1 ) was vigorously stirred with 1 mL HAuCl 4 (0.01 M) at room temperature for 3 h until complete dissolution. The resulting mixture was then transferred to a preheated oil bath, and a 0.5mL 2% sodium citrate solution was added. The reaction proceeded at 90°C for 15 min under continuous stirring [ 20 ]. Upon completion, the solution was cooled to room temperature, and the synthesized Au@MOF was stored for further use. A 100 µL aliquot of synthesized Au@MOF was mixed with 100 µL of Apt solution (4 µM Apt in PBS). Subsequently, the NaCl concentration was incrementally increased from 0.1 M to 0.2 M, followed by incubation at room temperature for 20 min. This salt-aging step was repeated in 0.1 M increments until a final concentration of 0.7 M NaCl was achieved. Unbound SH-Apt was removed via two rounds of centrifugation (11,000 rpm, 15 min) [ 21 ]. 2.4. Preparation of bacterial molecularly imprinted BPE First, E. coli O157:H7 (10 8 CFU mL − 1 ) and 3 mM PDA dissolved in 1× PBS were electrochemically polymerized on the surface of a bipolar electrode via cyclic voltammetry (CV) under nitrogen purging (15 min) to remove oxygen. Ten polymerization cycles were conducted within a potential range of -0.8 V to 0.8 V at a scan rate of 20 mV/s. To remove the E. coli O157:H7 template, a 5 wt% acetic acid/SDS solution was applied to the cathodic end of the electrode. After 18 h of incubation at room temperature, the electrode was rinsed with ultrapure water, yielding a template with bacterial-imprinted cavities. 2.5. ECL analysis A 10 µL aliquot of E. coli O157:H7 solution (10 0 -10 6 CFU mL − 1 ) was introduced at the cathodic end of a cavity template. After 1 hour incubation, the samples were rinsed twice with ultrapure water. Subsequently, they were incubated with 10 µL Apt-Au@MOF for an additional hour at room temperature, followed by two further washes with 1×PBS. Next, 10 µL of TMB/H 2 O 2 solution was added to the cathode, while 10 µL of ECL detection reagent was introduced at the anode. Finally, ECL signal detection was conducted by applying a constant potential of 5.6 V across the BPE for a response time of 20 seconds. 2.6. Real sample testing To evaluate the practical efficacy of the Au@MOF-integrated bacterial molecularly imprinted BPE sensor, real samples, including purified water, milk, and juice, were selected in accordance with the Chinese National Food Safety Standard (GB 7101 − 2022 for beverages). Each sample (100 µL) was diluted with 900 µL of 1×PBS, followed by spiking with 10 3 CFU mL − 1 of E. coli O157:H7. A constant potential of 5.6 V was applied to the electrode using an electrochemical workstation, and the ECL signal was recorded using a fluorescence spectrophotometer. 3. Results and discussion 3.1 Characterization of Au@MOF. The synthesis processes of Au@MOF were illustrated in Fig. 1 A. To confirm the successful synthesis of MOF and Au@MOF, SEM was employed to analyze their morphology. As shown in Fig. 2 A, octahedral MOF nanoparticles were observed. In the Au@MOF composite prepared using chloroauric acid as the precursor, AuNPs were uniformly distributed on the MOF surface (Fig. 2 B). EDS analysis was performed on both MOF and Au@MOF. Figure 2 C demonstrated the uniform distribution of C, O, and Fe, confirming the successful synthesis of the MOF. Furthermore, Fig. 2 D revealed the uniform distribution of AuNPs on the MOF surface, verifying the formation of Au@MOF. To further assess the catalytic performance of Au@MOF in TMB oxidation, the reaction mixture was analyzed using UV-vis spectroscopy. As depicted in Fig. 3 A, the UV-vis spectrum of the TMB solution showed significant changes within 2 min, with the appearance of a characteristic absorption peak at 450 nm, confirming the formation of TMB 2+ . Furthermore, colorimetric analysis of TMB oxidation catalyzed by different concentrations of Au@MOF revealed that the mixture of TMB and Au@MOF developed a distinct yellow-green color after 2 min (Fig. 3 B). The oxidation caused the formation of diamines, exhibiting a distinct yellow color solution and the green color was caused by the mixture of the initial blue product and the final yellow product [ 22 ]. The color intensity increased progressively with higher Au@MOF concentrations, further validating its catalytic role in TMB oxidation. 3.2. Characterization of the bacterial molecularly imprinted BPE. As illustrated in Fig. 1 B, E. coli O157:H7 was immobilized on the electrode surface via molecularly imprinting. Initially, a PDA film was formed on the cathode of BPE through the electropolymerization of DA with E. coli O157:H7. The bacterial cells were subsequently eluted, leaving behind an imprinted cavity complementary to E. coli O157:H7 on the cathode surface. The cavity was then re-exposed to E. coli O157:H7, enabling selective rebinding. The electrochemical polymerization of PDA was a complex process involving the oxidation of DA monomers on the electrode surface, followed by subsequent polymerization reactions. A simplified reaction scheme illustrating this process was presented below, accompanied by a detailed description: DA was oxidized on the electrode surface, yielding dopamine quinone while releasing electrons and protons (Eq. 1). Subsequently, dopamine quinone underwent intramolecular cyclization to form leukodopaminechrome (Eq. 2). Leukodopaminechrome was then further oxidized to produce dopaminechrome (Eq. 3). Finally, dopaminechrome molecules polymerized via covalent bonding and non-covalent interactions, such as hydrogen bonding and π-π stacking, resulting in the formation of polydopamine (Eq. 4). Cathodic reaction: Dopamine → Dopamine quinone + 2e − + 2H + (1) Dopamine quinone → Leukodopaminechrome (2) Leukodopaminechrome → Dopaminechrome + 2e − + 2H + (3) nDopaminechrome → (Polydopamine)n (4) To examine the sensor preparation process in greater detail, SEM was employed to characterize the surface morphology of both the bare BPE and the bacterial molecularly imprinted BPE. The bare BPE surface appeared relatively smooth (Fig. 2 E), whereas the bacterial molecularly imprinted BPE displayed numerous cavities (Fig. 2 F), confirming the successful loading of molecularly imprinted polymers onto the electrode surface. 3.3. Designing principle of E. coli O157:H7 detection. As illustrated in Fig. 1 A, the SH-Apt was immobilized onto the Au@MOF surface via Au-S bond formation and when E. coli O157:H7 was present, it specifically bound with the bacteria, enabling Au@MOF to selectively attach to the molecularly imprinted electrode as shown in Fig. 1 B. For enhancing detection sensitivity, TMB/H 2 O 2 was added on the cathode. The Au@MOF exhibited peroxidase-like activity and could catalyze the reduction reaction of TMB/H 2 O 2 system. Due to the electrical neutrality principle of the BPE, the oxidation reaction of [Ru(bpy) 3 ] 2+ /TPA system on the anode, generating a distinct ECL signal. A simplified reaction scheme illustrating this process was presented below (Eq. 5–11): Cathodic reaction: Fe 3+ + H 2 O 2 → Fe 2+ + ▪O 2 – +H + (5) Fe 2+ + H 2 O 2 → Fe 3+ + ▪OH + HO − (6) TMB +▪O 2 – +▪OH + H + → TMB n+ (n = 1,2) + H 2 O (7) Anodic reaction: Ru(bpy) 3 2+ - e − → Ru(bpy) 3 3+ (8) TPA - e − →TPA▪ + (9) TPA▪ + → TPA▪+ H + (10) TPA▪ + Ru(bpy) 3 3+ →Ru(bpy) 3 2+ *+ hv (11) Following the layered assembly of the electrodes, a BPE sensor modified with Au@MOF was fabricated. ECL detection was conducted on four electrode configurations: (1) the bare electrode, (2) the electrode after cavity formation and subsequent target adsorption, (3) the Au@MOF-modified electrode and (4) TMB/H 2 O 2 solution was added on the electrode. The ECL intensity of the bare electrode was measured at 1584 a.u., whereas the BPE adsorbing 10 3 CFU mL − 1 E. coli O157:H7 exhibited an intensity of 2602 a.u. The Au@MOF-modified BPE yielded a significantly higher ECL signal of 3277 a.u. Furthermore, upon applying 10 µL of TMB/H 2 O 2 solution to the cathode of the Au@MOF-modified electrode, the ECL signal increased to 5289 a.u. (Fig. 4 ). These results demonstrated that Au@MOF, in conjunction with TMB and H 2 O 2 as the detection medium, enhanced electron transfer efficiency, thereby amplifying the ECL intensity of the BPE. 3.4. Optimization of detection conditions The luminescence intensity of ECL is influenced by multiple factors. To optimize ECL intensity, we investigated the effects of applied driving voltage and SH-Apt incubation time. As shown in Fig. 5 A, the ECL intensity increases with voltage at 5.6 V, the signal growth in the experimental group slows, while the difference between the blank and experimental groups becomes more pronounced. Thus, 5.6 V was selected as the optimal driving voltage for subsequent experiments. The incubation time of bacteria with Apt-Au@MOF significantly influenced the luminescence intensity of [Ru(bpy) 3 ]2+ . This Au@MOF material exhibited catalytic redox activity, effectively enhancing the ECL signal. As shown in Fig. 5 B, the ECL signal began to gradually increase after 30 min of reaction, showed a sharp upward trend after 45 min, and reached a stable state after 60 min. Therefore, this study selected 60 min as the optimal incubation time. 3.4. Sensitivity of BPE-ECL Sensors Under optimized conditions, the BPE-ECL sensor was employed to detect E. coli O157:H7. As the concentration of E. coli O157:H7 increased, the ECL signal intensity exhibited a corresponding rise. A strong linear relationship was observed between the bacterial concentration (1-10 6 CFU mL − 1 ) and the ECL signal of [Ru(bpy) 3 ] 2+ (Fig. 6 A). The linear regression equation was determined as y = 3540 + 548.9 log C (y denoted the anode luminescence intensity, and C represented the concentration of E coli . O157:H7), with a correlation coefficient ( R 2 ) of 0.9952 (Fig. 6 B). Compared to previously reported bacterial detection methods, this approach demonstrated significantly improved sensitivity (Table 1 ). 3.5. Selectivity of BPE-ECL Sensor A comprehensive study was conducted to evaluate the binding selectivity of the prepared BPE-ECL sensor toward various bacterial strains, along with a detailed analysis of the corresponding ECL intensities. The binding affinity of the molecularly imprinted BPE sensor, functionalized with Au@MOF, was systematically investigated using three common foodborne pathogenic bacteria: E. coli O157:H7, Salmonella , and S. aureus. The results revealed that the BPE-ECL sensor exhibited remarkable selectivity for E. coli O157:H7. At a bacterial concentration of 10 3 CFU mL − 1 , the sensor generated a strong ECL signal of 3220 a.u. for E. coli O157:H7, while the signals for Salmonella and S. aureus remained close to the baseline (~ 1400 a.u.) (Fig. 6 C). These findings demonstrate that the developed sensor possesses high specificity and sensitivity for E. coli O157:H7 detection. 3.6. Real Sample Testing To further evaluate the applicability of the ECL sensor constructed by Au@MOF and bacterial molecular imprinting technology in food safety detection, diluted E. coli O157:H7 solutions of different concentrations (10 CFU mL − 1 , 100 CFU mL − 1 ) were added to bottled drinking water, milk and fruit juice respectively. Under optimized conditions, three repeated experiments were conducted using BPE-ECL to detect bacterial concentration. As shown in Fig. 6 D, the ECL signal values of three actual samples at different concentrations of E. coli O157:H7 indicate that the sensor has high precision and high sensitivity. These results indicate that this method is expected to be used for the quantitative detection of E. coli O157:H7 in actual food samples and has broad application prospects in related fields. Table 1 Comparison of different bacteria sensors. Method System Detection range (CFU mL − 1 ) Detection limit (CFU mL − 1 ) Reference LFIA PDA functionalized AuNPs 10 2 ~10 7 10 2 [ 23 ] ELISA PDA-based FeCoMOF/Co 3 O 4 nanoenzymes 10 1 ~10 8 2 [ 24 ] LC-based Fabric mesh-anchored liquid crystal platform utilizing the cationic surfactant cetyltrimethylammonium bromide (CTAB) 10 1 ~10 6 6 [ 25 ] Fluorescent Combine CDs with covalent organic frameworks (COFs) 0 ~ 10 6 7 [ 26 ] PCR Whole-cell imprinted microarray platform 10 ~ 10 7 1 [ 27 ] BPE-ECL Au@MOF 1 ~ 10 6 1 This article 4. Conclusion This study developed an ECL sensor by integrating the Au@MOF structure with a bacterial molecularly imprinted BPE for the detection of E. coli O157:H7. The sensor was fabricated by electrochemically polymerizing PDA and E. coli O157:H7 on the cathode of the BPE, thereby forming highly specific recognition sites. The MOF structure can catalyze redox reactions, and the further synthesized Au@MOF nanocomposites, after modification with SH-Apt, can specifically recognize the target bacteria. Then, the Au@MOF can catalyze the reduction reaction of the TMB/H 2 O 2 system. Due to the electro-neutrality principle of the BPE, the oxidation reaction of the [Ru(bpy) 3 ] 2+ /TPA system on the anode generates a distinct ECL signal. The sensor has a wide linear detection range (1-10 6 CFU mL − 1 ) and an ultralow detection limit (1 CFU mL − 1 ), demonstrating excellent analytical performance. Additionally, the sensor shows high selectivity for E. coli O157:H7 and can effectively distinguish it from Salmonella and S. aureus. The combination of bacterial molecularly imprinted technology with Au@MOF for ECL detection provides a promising platform for rapid and accurate pathogen detection. Declarations Author contribution Yunlong Liu: Writing – review & editing. Panpan Liu: Formal analysis, Writing – review & editing. Mengjuan Li: Validation, Writing – review & editing. Fengyang Wang: Validation, Writing – review & editing. Yusong Wan, Yan Qi and Lei Ji: Validation, Writing – review & editing. Xiaohui Xiong: Formal analysis, Conceptualization, Methodology, Funding acquisition, Project administration. Yuanjian Liu: Funding acquisition, Writing – review & editing. Funding This work was financially supported by the Postgraduate Research and Practice Innovation Programme Projects of Jiangsu (No. SJCX24_0497). Data availability All data provided by this article are available on request from the corresponding author. Ethical approval This study did not involve human or animal subjects, and thus, no ethical approval was required. Conflict of interest The authors declare no competing interests. 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Analyst 148: 869-875. https://doi.org/10.1039/D2AN01914K Zeng RX, Zhou FF, Wang YH, Liao ZX, Qian SH, Luo Q, Zheng JP (2024) Polydopamine Modified Colloidal Gold Nanotag-Based Lateral Flow Immunoassay Platform for Highly Sensitive Detection of Pathogenic Bacteria and Fast Evaluation of Antibacterial Agents. Talanta 278: 126525. https://doi.org/10.1016/j.talanta.2024.126525 Jiang SJ, Wu JB, Xu LX, Yun J, Lu ZW, Wang YY, Sun MM, Rao HB (2025) A Dual-Mode Biosensing Platform Based on Polydopamine-Modified FeCoMOF/Co 3 O 4 Nanoenzyme for Sensitive Detection of Escherichia coli O157:H7. Talanta 295: 128295. https://doi.org/10.1016/j.talanta.2025.128295 Mostajabodavati S, Mousavizadegan M, Hosseini M, Mohammadimasoudi M, Mohammadi J (2024) Machine Learning-Assisted Liquid Crystal-Based Aptasensor for the Specific Detection of Whole-Cell Escherichia coli in Water and Food. Food Chem 448: 139113. https://doi.org/10.1016/j.foodchem.2024.139113 Wang SL, Liang NN, Hu XT, Li WT, Guo Z, Zhang XA, Huang XW, Li ZH, Zou XB, Shi JY (2024) Carbon Dots and Covalent Organic Frameworks Based FRET Immunosensor for Sensitive Detection of Escherichia coli O157:H7. Food Chem 447: 138663. https://doi.org/10.1016/j.foodchem.2024.138663 Zhang JS, Liu XM, Li ZQ, Li X, Li QJ, Li WW, Li JL (2025) Whole-Cell Molecularly Imprinted Fluorescent Photonic Microsphere Microarray for High-Throughput Detection of Foodborne Pathogens. Anal Chem 97: 9779-9788. https://doi.org/10.1021/acs.analchem.4c06821 Additional Declarations No competing interests reported. Supplementary Files Onlinefloatimage1.png Graphical abstract Schematic Diagram of the BPE-ECL biosensor based on bacterial molecularly imprint and Au@MOF. Onlinefloatimage1.png Graphical abstract Schematic Diagram of the BPE-ECL biosensor based on bacterial molecularly imprint and Au@MOF. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7210225","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494583731,"identity":"827c679e-3ba7-4ea6-935b-a3b6ad69816e","order_by":0,"name":"Yunlong Liu","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Yunlong","middleName":"","lastName":"Liu","suffix":""},{"id":494583732,"identity":"cdf5501f-9f44-4ab3-9235-7b49332fb91d","order_by":1,"name":"Panpan Liu","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Panpan","middleName":"","lastName":"Liu","suffix":""},{"id":494583733,"identity":"a83ce281-165f-44d9-9b72-c38dac228347","order_by":2,"name":"Mengjuan Li","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Mengjuan","middleName":"","lastName":"Li","suffix":""},{"id":494583734,"identity":"ab531113-4ceb-4411-acbc-833efdb7da5a","order_by":3,"name":"Fengyang Wang","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Fengyang","middleName":"","lastName":"Wang","suffix":""},{"id":494583735,"identity":"437a214f-3c75-4f4d-985b-5c309d9a32ba","order_by":4,"name":"Yusong Wan","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Yusong","middleName":"","lastName":"Wan","suffix":""},{"id":494583736,"identity":"d0c2ef86-9e1c-4661-830e-93ab58a0bdb2","order_by":5,"name":"Yan Qi","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Yan","middleName":"","lastName":"Qi","suffix":""},{"id":494583737,"identity":"22ebf4cd-3743-4684-954f-e45e87e522c5","order_by":6,"name":"Lei Ji","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Lei","middleName":"","lastName":"Ji","suffix":""},{"id":494583738,"identity":"8e482065-c769-4293-a2ba-27123675217e","order_by":7,"name":"Xiaohui Xiong","email":"","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Xiaohui","middleName":"","lastName":"Xiong","suffix":""},{"id":494583739,"identity":"e2f61fd7-2e32-4501-9928-e8a5f88fd667","order_by":8,"name":"Yuanjian Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxElEQVRIiWNgGAWjYBACPiA+AGUzPkioqCGshQ2hhZnZ4MGZY8RpgQJmNsmHLcxEaJFIfnjgxx8GeYNr549VJDawMfC3dycQ0JJmcLC3jcFww+1kthuJO2QYJM6c3UBASw7DAd4GhgQDsJYzbAwGErmEtRz88weipSCxjZk4LYd52CBaGIjTwvPM4LAs0C8zbycbSyScOcZD0C/87MmPP74Bhhjf7cSHH39U1Mjxt/fi1wIF/+EsHmKUj4JRMApGwSggAAB5UETY2I+P3gAAAABJRU5ErkJggg==","orcid":"","institution":"Coll Food Sci \u0026 Light Ind, Nanjing Tech University","correspondingAuthor":true,"prefix":"","firstName":"Yuanjian","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2025-07-25 04:23:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7210225/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7210225/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88370930,"identity":"97aff252-1ef8-4431-a8e4-b1b1a5ef9abd","added_by":"auto","created_at":"2025-08-05 19:08:06","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":90464,"visible":true,"origin":"","legend":"\u003cp\u003e(A) The synthesis procedure of the Apt-Au@MOF. (B) The mechanism of \u003cem\u003eE. coli\u003c/em\u003e O157:H7 detection based on bacterial molecularly imprinted BPE and Au@MOF.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/fc8b8b1ac1107aad5a5f65fc.jpg"},{"id":88370931,"identity":"e688ac86-b6cc-4445-9080-ff81fb01bace","added_by":"auto","created_at":"2025-08-05 19:08:06","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":192617,"visible":true,"origin":"","legend":"\u003cp\u003eThe SEM images of MOF (A) and Au@MOF (B). The elemental analysis of MOF (C) and Au@MOF (D). The SEM images of bare BPE (E) and bacterial molecularly imprinted BPE (F).\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/f32d30490eb3e73f36ba062f.jpg"},{"id":88370933,"identity":"3a745ee7-d2e7-4c14-96cb-cfdbd480198a","added_by":"auto","created_at":"2025-08-05 19:08:06","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":71711,"visible":true,"origin":"","legend":"\u003cp\u003e(A) UV-vis absorption spectra of TMB and its oxidation by H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e catalyzed by Au@MOF. (B) Chromogenic reaction of TMB oxidation by H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e catalyzed by Au@MOF.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/c57ce384fd50b50d295a1699.jpg"},{"id":88371533,"identity":"e1656db0-bdf9-44d7-99a6-adb43338f37c","added_by":"auto","created_at":"2025-08-05 19:16:06","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":46510,"visible":true,"origin":"","legend":"\u003cp\u003eThe ECL signal of anode with different cathode (Bare BPE; BPE modified with the target 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e-1\u003c/sup\u003e \u003cem\u003eE. coli\u003c/em\u003e O157:H7; BPE modified with the target 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e-1\u003c/sup\u003e \u003cem\u003eE. coli\u003c/em\u003e O157:H7 and Apt-Au@MOF; TMB solution was dropped on the BPE modified with the target 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e-1\u003c/sup\u003e \u003cem\u003eE. coli\u003c/em\u003e O157:H7 and Apt-Au@MOF) with an applied driving voltage of 5.6 V.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/0a5a95a6a2ffa3380fb06673.jpg"},{"id":88371535,"identity":"4835634a-14b0-452a-bd12-f7400f0a8410","added_by":"auto","created_at":"2025-08-05 19:16:06","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":55648,"visible":true,"origin":"","legend":"\u003cp\u003e(A) ECL signal values under different driving voltages, red line (10 µL 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e-1\u003c/sup\u003e \u003cem\u003eE. coli\u003c/em\u003e O157:H7) and black line (10 µL PBS). Both groups were incubated for 60 min. (B) The ECL intensity of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e in combination with Apt-Au@MOF and 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e-1\u003c/sup\u003e \u003cem\u003eE. coli\u003c/em\u003e O157:H7 at different incubation times. The applied voltage was 5.6 V. (Anode: 10 µL ECL detection solution; Cathode: 10 µL TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution.)\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/aec37d4bf816cdcc3422f348.jpg"},{"id":88371885,"identity":"4083d26b-cbd4-4b0a-9b58-81cf60431f83","added_by":"auto","created_at":"2025-08-05 19:24:06","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":93955,"visible":true,"origin":"","legend":"\u003cp\u003e(A) ECL-wavelength response of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e on the anode of BPE-ECL sensor incubated with different concentrations of \u003cem\u003eE. coli\u003c/em\u003e O157:H7. (B) Calibration curve corresponding to the value of ECL intensity as a function of the logarithm concentration of \u003cem\u003eE. coli\u003c/em\u003e O157:H7. (C) ECL intensity of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e for different pathogenic bacteria in bottled water. (D) ECL intensity of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e for different concentrations of \u003cem\u003eE. coli\u003c/em\u003e O157:H7 (blank, 10 CFU mL\u003csup\u003e-1\u003c/sup\u003e and 100 CFU mL\u003csup\u003e-1\u003c/sup\u003e) in bottled water, juice, and milk. (Anode: 10 µL ECL detection solution; Cathode: 10 µL TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution; Applied voltage: 5.6 V).\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/8f6db44a843289ac915f4ffa.jpg"},{"id":88590238,"identity":"976a7ffe-6627-48c1-b200-2fa82faaf094","added_by":"auto","created_at":"2025-08-08 05:32:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1370230,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/70739929-479e-45c6-862d-12c8ff3036fb.pdf"},{"id":88371532,"identity":"17a8922d-5ae1-4e3f-8295-018c8cc23738","added_by":"auto","created_at":"2025-08-05 19:16:06","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":78042,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical abstract\u003c/p\u003e\n\u003cp\u003eSchematic Diagram of the BPE-ECL biosensor based on bacterial molecularly imprint and Au@MOF.\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/c3628c1e9bc1df3f3f9f0a64.png"},{"id":88370964,"identity":"008aaf6c-fcb2-41cc-a7b8-fdd75cd01636","added_by":"auto","created_at":"2025-08-05 19:08:07","extension":"png","order_by":31,"title":"","display":"","copyAsset":false,"role":"supplement","size":78042,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical abstract\u003c/p\u003e\n\u003cp\u003eSchematic Diagram of the BPE-ECL biosensor based on bacterial molecularly imprint and Au@MOF.\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7210225/v1/48b035ed85077ed684c4cad6.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Detection of E. coli O157:H7 using bacterial molecularly imprinted bipolar electrode and Au@metal-organic framework","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eFood safety issues significantly impact public health and represent a critical concern that warrants immediate attention. These issues are intricately linked to human health and have profound consequences on economic and social development [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The causes of foodborne diseases are diverse and multifactorial, involving bacteria, fungi, viruses, parasites, and chemical contaminants present in food. Among these, foodborne pathogens are the predominant contributors to such diseases [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. As environmental pollution intensifies, pathogens can rapidly proliferate and spread, exacerbating health-related issues. Consequently, it is imperative to develop rapid and sensitive bacterial detection methods for early clinical diagnosis [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e][\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Although traditional culture-based detection methods are reliable, they are often cumbersome, time-consuming, and limited in sensitivity. In contrast, non-culture detection technologies, such as mass spectrometry, colloidal gold assays, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assays (ELISA), offer improved sensitivity and reduced analysis time [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, these techniques still face challenges, including complex sample preparation, high costs, and the need for skilled personnel [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e][\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e][\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eElectrochemiluminescence (ECL) is an effective biosensing technology known for its high sensitivity, strong selectivity, good controllability, and ease of operation [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The recognition element is a critical component, significantly influencing both selectivity and sensitivity. One reported amplification strategy involves utilizing nanomaterials as electrochemical modifiers to enhance the detected ECL signal [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Metal-organic frameworks (MOFs), which are porous materials with a crystalline structure, are advanced materials formed from metal ions/clusters and organic ligands through coordination reactions. These frameworks can form three-dimensional structures with distinctive properties that promote substrate diffusion. MOFs typically feature active components, functionalized pore surfaces, high surface-to-volume ratios, and large pore volumes [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e][\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. MOF-modified electrodes containing electroactive substances can significantly improve electrode conductivity, thereby enhancing sensor sensitivity. Gupta et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] developed an electrochemical sensor based on an iron-based MOF (MIL-53) for detecting \u003cem\u003eEscherichia coli\u003c/em\u003e (\u003cem\u003eE. coli\u003c/em\u003e). They combined polystyrene sulfonate (PEDOT: PSS) with MIL-53 to introduce electrochemical activity and optimized the encapsulation amount of PEDOT: PSS within the MOF pores to achieve optimal conductivity. The composite material, due to its specific antibodies against E. coli, was used to modify screen-printed electrodes (SPE). By employing differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS), E. coli was detected across a wide concentration range of 2.1 \u0026times; 10\u003csup\u003e2\u003c/sup\u003e to 2.1 \u0026times; 10\u003csup\u003e8\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with a detection limit of 4.0 CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eMolecularly imprinted polymers (MIPs) are rigid structures formed by the copolymerization of functional and crosslinking monomers in the presence of a molecular template. This templated synthesis enables the self-organization of functional monomers around the template, while the crosslinking monomer solidifies their positions into a rigid matrix. Once the template is removed, cavities are formed within the MIP, exhibiting complementary characteristics in size, spatial shape, and the distribution of chemical functional groups relative to the target molecule. These features confer high-affinity and selective binding sites for the template [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Electropolymerization is the process of electrolysis conducted in an electrolytic cell containing an appropriate electrolyte, using specific electrochemical methods. During this process, monomers on the electrode surface undergo oxidation, reduction, or decomposition, generating intermediates such as free radicals or ions, which initiate polymerization reactions. Electropolymerization is a powerful tool for generating uniform films on electrodes and allows easy adjustment of film thickness by varying the number of deposition cycles [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. However, a limitation of this technique is the restricted range of monomers that can undergo electropolymerization, which limits the possibilities for MIP synthesis. Reports suggest that dopamine, as an electropolymerizable monomer, can interact with various templates through non-covalent interactions such as π-π stacking, electrostatic interactions, and hydrogen bonding [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePolydopamine (PDA) is a biomimetic polymer first identified in 2007 [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Inspired by the adhesive proteins found in marine mussels, which are rich in dopamine (DA) and lysine, early studies revealed that DA undergoes self-oxidation to dopamine-quinone, which subsequently cyclizes to form 5,6-dihydroxyindole (DHI), a critical precursor to PDA. Additionally, the amine and catechol functional groups of polydopamine promote metal-ion coordination [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. For instance, Yang et al. developed PDA-coated nanocomposites that feature a MOF shell encasing a nanoparticle core [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis study developed a bipolar electrode (BPE) sensor by integrating Au@MOF with bacterial molecularly imprint for the detection of \u003cem\u003eE. coli\u003c/em\u003e O157:H7. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, bacterial molecularly imprint provides selective cavity adsorption of \u003cem\u003eE. coli\u003c/em\u003e O157:H7, while Au@MOF facilitating redox reactions. By introducing SH-Apt, Au@MOF was effectively immobilized onto the cathodic end of BPE. The subsequent addition of 3,3\u0026prime;,5,5\u0026prime;-tetramethylbenzidine (TMB), a redox-active substrate, further amplified the ECL signal. The resulting sensor exhibited high sensitivity and specificity for \u003cem\u003eE. coli\u003c/em\u003e O157:H7, demonstrating considerable potential for practical applications.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"2. Experimental part","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials and apparatus\u003c/h2\u003e\u003cp\u003e\u003cem\u003eE. coli\u003c/em\u003e O157:H7 (CICC 10907), \u003cem\u003eSalmonella typhimurium\u003c/em\u003e (\u003cem\u003eS. typhimurium\u003c/em\u003e, ATCC 14028) and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e (\u003cem\u003eS. aureus\u003c/em\u003e, ATCC 29213) came from Guangdong Microbial Culture and Collection Center (GDMCC). Ternary pyridine hexahydrate ruthenium chloride (Ru(bpy)\u003csub\u003e3\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e.6H\u003csub\u003e2\u003c/sub\u003eO) and tripropylamine (TPA) were acquired from Sigma-Aldrich Ltd. (St. Louis, Missouri, USA). LB broth (CICC10907) was obtained from Qingdao Haibo Biotechnology Co., Ltd. (Qingdao China). H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, HAuCl\u003csub\u003e4\u003c/sub\u003e, terephthalic acid (H\u003csub\u003e2\u003c/sub\u003eBDC), FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, ethanol, dopamine (DA), 3,3',5,5'-tetramethylbenzidine (TMB) and anhydrous sodium acetate were procured from Nanjing Wanqing Chemical Glassware \u0026amp; Instrument Co., Ltd. (Nanjing China). Sodium citrate was procured from Tianjin Xiansi Aopude Technology Co., Ltd. (Tianjin China). Sodium dodecyl sulfate (SDS) was procured from Shanghai Macklin Biochemical Technology Co., Ltd. (Shanghai China). N, N-Dimethylformamide (DMF) was procured from Shanghai Meirui Biochemical Technology Co., Ltd. (Shanghai China). Thiolated aptamer for \u003cem\u003eE. coli\u003c/em\u003e O157:H7 (SH-Apt): 5\u0026prime;-SH-TGA GCC CAA GCC CTG GTA TGC GGA TAA CGA GGT ATT CAC GAC TGG TCG TCA GGT ATG GTT GGC AGG TCT ACT TTG GGA TC-3\u0026prime; was synthesized by Sangon Biotech Co., Ltd. (Shanghai, China).\u003c/p\u003e\u003cp\u003eThe following buffer solutions were used in this study: PBS (pH 7.2\u0026ndash;7.4, containing 136.89 mM sodium chloride, 2.67 mM potassium chloride, 8.24 mM disodium hydrogen phosphate, and 1.76 mM sodium dihydrogen phosphate); ECL detection solution (PBS with 50 mM [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e and 250 mM TPA, prepared fresh daily); dopamine electropolymerization buffer solution (1\u0026times;PBS containing 3 mM dopamine, pH 6.5, deoxygenated with nitrogen gas for 15 min); and TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution (1 mL total volume, comprising 890 \u0026micro;L sodium acetate, 100 \u0026micro;L of 10 mM TMB, and 10 \u0026micro;L of 10 mM H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e). All buffers were prepared using an ultra-pure water system (GWA-UN1-F40, Persee, China) with a specific resistance of 18.2 MΩ\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn this experiment, all electrochemical measurements were conducted using a CHI750E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd., China). The ECL signal of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e (λ\u003csub\u003emax\u003c/sub\u003e,\u003csub\u003eem\u003c/sub\u003e = 620 nm) was detected with a fluorescence spectrophotometer (Fmur4700, Hitachi, Japan), operating at a scanning speed of 12,000 nm/min, in strict accordance with the parameters established in our previous work [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The microstructural morphology and elemental distribution during the synthesis of MOF, Au@MOF, and BPE cathodes were systematically characterized using scanning electron microscopy (SEM; ZEISS Sigma 360 1) and energy-dispersive X-ray spectroscopy (EDS; Ultim Max 65). UV-vis spectra were obtained by a Rayleigh UV-1601 spectrophotometer (Beifen-Ruili Analytical Instrument Company. Limited, China).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Bacteria culture\u003c/h2\u003e\u003cp\u003e\u003cem\u003eE. coli\u003c/em\u003e O157:H7 was inoculated into Luria-Bertani (LB) medium and incubated at 37\u0026deg;C for 18\u0026ndash;24 h with shaking at 160 rpm. The bacterial suspension was washed, resuspended to a concentration of 10\u003csup\u003e8\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and then serially diluted tenfold to achieve the desired concentration.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Preparation of Apt-Au@MOF\u003c/h2\u003e\u003cp\u003eThe MOF was synthesized via a hydrothermal method [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Specifically, 0.126 g of H\u003csub\u003e2\u003c/sub\u003eBDC and 0.187 g of FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO were dissolved in 15 mL of DMF. Subsequently, 1.67 mL of acetic acid was added, and the mixture was stirred until complete dissolution. The homogeneous solution was then transferred to a preheated oil bath and stirred at 120\u0026deg;C for 4 h. Upon completion of the reaction, the solution was cooled to room temperature naturally. The product was isolated via centrifugation and washed sequentially with DMF, ethanol, and deionized water to remove residual reactants. The resulting precipitate was collected and stored in deionized water.\u003c/p\u003e\u003cp\u003eA 5 mL MOF solution (1 mg mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was vigorously stirred with 1 mL HAuCl\u003csub\u003e4\u003c/sub\u003e (0.01 M) at room temperature for 3 h until complete dissolution. The resulting mixture was then transferred to a preheated oil bath, and a 0.5mL 2% sodium citrate solution was added. The reaction proceeded at 90\u0026deg;C for 15 min under continuous stirring [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Upon completion, the solution was cooled to room temperature, and the synthesized Au@MOF was stored for further use.\u003c/p\u003e\u003cp\u003eA 100 \u0026micro;L aliquot of synthesized Au@MOF was mixed with 100 \u0026micro;L of Apt solution (4 \u0026micro;M Apt in PBS). Subsequently, the NaCl concentration was incrementally increased from 0.1 M to 0.2 M, followed by incubation at room temperature for 20 min. This salt-aging step was repeated in 0.1 M increments until a final concentration of 0.7 M NaCl was achieved. Unbound SH-Apt was removed via two rounds of centrifugation (11,000 rpm, 15 min) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Preparation of bacterial molecularly imprinted BPE\u003c/h2\u003e\u003cp\u003eFirst, \u003cem\u003eE. coli\u003c/em\u003e O157:H7 (10\u003csup\u003e8\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and 3 mM PDA dissolved in 1\u0026times; PBS were electrochemically polymerized on the surface of a bipolar electrode via cyclic voltammetry (CV) under nitrogen purging (15 min) to remove oxygen. Ten polymerization cycles were conducted within a potential range of -0.8 V to 0.8 V at a scan rate of 20 mV/s. To remove the \u003cem\u003eE. coli\u003c/em\u003e O157:H7 template, a 5 wt% acetic acid/SDS solution was applied to the cathodic end of the electrode. After 18 h of incubation at room temperature, the electrode was rinsed with ultrapure water, yielding a template with bacterial-imprinted cavities.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. ECL analysis\u003c/h2\u003e\u003cp\u003eA 10 \u0026micro;L aliquot of \u003cem\u003eE. coli\u003c/em\u003e O157:H7 solution (10\u003csup\u003e0\u003c/sup\u003e-10\u003csup\u003e6\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was introduced at the cathodic end of a cavity template. After 1 hour incubation, the samples were rinsed twice with ultrapure water. Subsequently, they were incubated with 10 \u0026micro;L Apt-Au@MOF for an additional hour at room temperature, followed by two further washes with 1\u0026times;PBS. Next, 10 \u0026micro;L of TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution was added to the cathode, while 10 \u0026micro;L of ECL detection reagent was introduced at the anode. Finally, ECL signal detection was conducted by applying a constant potential of 5.6 V across the BPE for a response time of 20 seconds.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Real sample testing\u003c/h2\u003e\u003cp\u003eTo evaluate the practical efficacy of the Au@MOF-integrated bacterial molecularly imprinted BPE sensor, real samples, including purified water, milk, and juice, were selected in accordance with the Chinese National Food Safety Standard (GB 7101\u0026thinsp;\u0026minus;\u0026thinsp;2022 for beverages). Each sample (100 \u0026micro;L) was diluted with 900 \u0026micro;L of 1\u0026times;PBS, followed by spiking with 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of \u003cem\u003eE. coli\u003c/em\u003e O157:H7. A constant potential of 5.6 V was applied to the electrode using an electrochemical workstation, and the ECL signal was recorded using a fluorescence spectrophotometer.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e\u003cem\u003e3.1 Characterization of Au@MOF.\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe synthesis processes of Au@MOF were illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA. To confirm the successful synthesis of MOF and Au@MOF, SEM was employed to analyze their morphology. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA, octahedral MOF nanoparticles were observed. In the Au@MOF composite prepared using chloroauric acid as the precursor, AuNPs were uniformly distributed on the MOF surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). EDS analysis was performed on both MOF and Au@MOF. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC demonstrated the uniform distribution of C, O, and Fe, confirming the successful synthesis of the MOF. Furthermore, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD revealed the uniform distribution of AuNPs on the MOF surface, verifying the formation of Au@MOF.\u003c/p\u003e\u003cp\u003eTo further assess the catalytic performance of Au@MOF in TMB oxidation, the reaction mixture was analyzed using UV-vis spectroscopy. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003eA, the UV-vis spectrum of the TMB solution showed significant changes within 2 min, with the appearance of a characteristic absorption peak at 450 nm, confirming the formation of TMB\u003csup\u003e2+\u003c/sup\u003e. Furthermore, colorimetric analysis of TMB oxidation catalyzed by different concentrations of Au@MOF revealed that the mixture of TMB and Au@MOF developed a distinct yellow-green color after 2 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). The oxidation caused the formation of diamines, exhibiting a distinct yellow color solution and the green color was caused by the mixture of the initial blue product and the final yellow product [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The color intensity increased progressively with higher Au@MOF concentrations, further validating its catalytic role in TMB oxidation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Characterization of the bacterial molecularly imprinted BPE.\u003c/h2\u003e\u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB, E. \u003cem\u003ecoli\u003c/em\u003e O157:H7 was immobilized on the electrode surface via molecularly imprinting. Initially, a PDA film was formed on the cathode of BPE through the electropolymerization of DA with \u003cem\u003eE. coli\u003c/em\u003e O157:H7. The bacterial cells were subsequently eluted, leaving behind an imprinted cavity complementary to \u003cem\u003eE. coli\u003c/em\u003e O157:H7 on the cathode surface. The cavity was then re-exposed to \u003cem\u003eE. coli\u003c/em\u003e O157:H7, enabling selective rebinding. The electrochemical polymerization of PDA was a complex process involving the oxidation of DA monomers on the electrode surface, followed by subsequent polymerization reactions. A simplified reaction scheme illustrating this process was presented below, accompanied by a detailed description:\u003c/p\u003e\u003cp\u003eDA was oxidized on the electrode surface, yielding dopamine quinone while releasing electrons and protons (Eq.\u0026nbsp;1). Subsequently, dopamine quinone underwent intramolecular cyclization to form leukodopaminechrome (Eq.\u0026nbsp;2). Leukodopaminechrome was then further oxidized to produce dopaminechrome (Eq.\u0026nbsp;3). Finally, dopaminechrome molecules polymerized via covalent bonding and non-covalent interactions, such as hydrogen bonding and π-π stacking, resulting in the formation of polydopamine (Eq.\u0026nbsp;4).\u003c/p\u003e\u003cp\u003eCathodic reaction:\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDopamine \u0026rarr; Dopamine quinone\u0026thinsp;+\u0026thinsp;2e\u003csup\u003e\u0026minus;\u003c/sup\u003e+ 2H\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(1)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDopamine quinone \u0026rarr; Leukodopaminechrome\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(2)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeukodopaminechrome \u0026rarr; Dopaminechrome\u0026thinsp;+\u0026thinsp;2e\u003csup\u003e\u0026minus;\u003c/sup\u003e+ 2H\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003enDopaminechrome \u0026rarr; (Polydopamine)n\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTo examine the sensor preparation process in greater detail, SEM was employed to characterize the surface morphology of both the bare BPE and the bacterial molecularly imprinted BPE. The bare BPE surface appeared relatively smooth (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE), whereas the bacterial molecularly imprinted BPE displayed numerous cavities (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eF), confirming the successful loading of molecularly imprinted polymers onto the electrode surface.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Designing principle of E. coli O157:H7 detection.\u003c/h2\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA, the SH-Apt was immobilized onto the Au@MOF surface via Au-S bond formation and when \u003cem\u003eE. coli\u003c/em\u003e O157:H7 was present, it specifically bound with the bacteria, enabling Au@MOF to selectively attach to the molecularly imprinted electrode as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB.\u003c/p\u003e\u003cp\u003eFor enhancing detection sensitivity, TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was added on the cathode. The Au@MOF exhibited peroxidase-like activity and could catalyze the reduction reaction of TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system. Due to the electrical neutrality principle of the BPE, the oxidation reaction of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e/TPA system on the anode, generating a distinct ECL signal. A simplified reaction scheme illustrating this process was presented below (Eq.\u0026nbsp;5\u0026ndash;11):\u003c/p\u003e\u003cp\u003eCathodic reaction:\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe\u003csup\u003e3+\u003c/sup\u003e + H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e \u0026rarr; Fe\u003csup\u003e2+\u003c/sup\u003e + ▪O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e+H\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(5)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe\u003csup\u003e2+\u003c/sup\u003e + H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026rarr; Fe\u003csup\u003e3+\u003c/sup\u003e + ▪OH\u0026thinsp;+\u0026thinsp;HO\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(6)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTMB +▪O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e+▪OH\u0026thinsp;+\u0026thinsp;H\u003csup\u003e+\u003c/sup\u003e \u0026rarr; TMB\u003csup\u003en+\u003c/sup\u003e(n\u0026thinsp;=\u0026thinsp;1,2)\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(7)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"2\"\u003eAnodic reaction:\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabc\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRu(bpy)\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e - e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; Ru(bpy)\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e3+\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(8)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPA - e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr;TPA▪\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(9)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPA▪\u003csup\u003e+\u003c/sup\u003e \u0026rarr; TPA▪+ H\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(10)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTPA▪ + Ru(bpy)\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e3+\u003c/sup\u003e \u0026rarr;Ru(bpy)\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e *+ hv\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(11)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFollowing the layered assembly of the electrodes, a BPE sensor modified with Au@MOF was fabricated. ECL detection was conducted on four electrode configurations: (1) the bare electrode, (2) the electrode after cavity formation and subsequent target adsorption, (3) the Au@MOF-modified electrode and (4) TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution was added on the electrode. The ECL intensity of the bare electrode was measured at 1584 a.u., whereas the BPE adsorbing 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e \u003cem\u003eE. coli\u003c/em\u003e O157:H7 exhibited an intensity of 2602 a.u. The Au@MOF-modified BPE yielded a significantly higher ECL signal of 3277 a.u. Furthermore, upon applying 10 \u0026micro;L of TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution to the cathode of the Au@MOF-modified electrode, the ECL signal increased to 5289 a.u. (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e). These results demonstrated that Au@MOF, in conjunction with TMB and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e as the detection medium, enhanced electron transfer efficiency, thereby amplifying the ECL intensity of the BPE.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Optimization of detection conditions\u003c/h2\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe luminescence intensity of ECL is influenced by multiple factors. To optimize ECL intensity, we investigated the effects of applied driving voltage and SH-Apt incubation time. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eA, the ECL intensity increases with voltage at 5.6 V, the signal growth in the experimental group slows, while the difference between the blank and experimental groups becomes more pronounced. Thus, 5.6 V was selected as the optimal driving voltage for subsequent experiments.\u003c/p\u003e\u003cp\u003eThe incubation time of bacteria with Apt-Au@MOF significantly influenced the luminescence intensity of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e]2+\u003c/sup\u003e. This Au@MOF material exhibited catalytic redox activity, effectively enhancing the ECL signal. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eB, the ECL signal began to gradually increase after 30 min of reaction, showed a sharp upward trend after 45 min, and reached a stable state after 60 min. Therefore, this study selected 60 min as the optimal incubation time.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Sensitivity of BPE-ECL Sensors\u003c/h2\u003e\u003cp\u003eUnder optimized conditions, the BPE-ECL sensor was employed to detect \u003cem\u003eE. coli\u003c/em\u003e O157:H7. As the concentration of \u003cem\u003eE. coli\u003c/em\u003e O157:H7 increased, the ECL signal intensity exhibited a corresponding rise. A strong linear relationship was observed between the bacterial concentration (1-10\u003csup\u003e6\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and the ECL signal of [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eA). The linear regression equation was determined as \u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;3540\u0026thinsp;+\u0026thinsp;548.9 log\u003cem\u003eC\u003c/em\u003e (y denoted the anode luminescence intensity, and \u003cem\u003eC\u003c/em\u003e represented the concentration of \u003cem\u003eE coli\u003c/em\u003e. O157:H7), with a correlation coefficient (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e) of 0.9952 (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eB). Compared to previously reported bacterial detection methods, this approach demonstrated significantly improved sensitivity (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.5. Selectivity of BPE-ECL Sensor\u003c/h2\u003e\u003cp\u003eA comprehensive study was conducted to evaluate the binding selectivity of the prepared BPE-ECL sensor toward various bacterial strains, along with a detailed analysis of the corresponding ECL intensities. The binding affinity of the molecularly imprinted BPE sensor, functionalized with Au@MOF, was systematically investigated using three common foodborne pathogenic bacteria: \u003cem\u003eE. coli\u003c/em\u003e O157:H7, \u003cem\u003eSalmonella\u003c/em\u003e, and \u003cem\u003eS.\u003c/em\u003e aureus. The results revealed that the BPE-ECL sensor exhibited remarkable selectivity for \u003cem\u003eE. coli\u003c/em\u003e O157:H7. At a bacterial concentration of 10\u003csup\u003e3\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the sensor generated a strong ECL signal of 3220 a.u. for \u003cem\u003eE. coli\u003c/em\u003e O157:H7, while the signals for \u003cem\u003eSalmonella\u003c/em\u003e and \u003cem\u003eS.\u003c/em\u003e aureus remained close to the baseline (~\u0026thinsp;1400 a.u.) (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eC). These findings demonstrate that the developed sensor possesses high specificity and sensitivity for \u003cem\u003eE. coli\u003c/em\u003e O157:H7 detection.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.6. Real Sample Testing\u003c/h2\u003e\u003cp\u003eTo further evaluate the applicability of the ECL sensor constructed by Au@MOF and bacterial molecular imprinting technology in food safety detection, diluted \u003cem\u003eE. coli\u003c/em\u003e O157:H7 solutions of different concentrations (10 CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 100 CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) were added to bottled drinking water, milk and fruit juice respectively. Under optimized conditions, three repeated experiments were conducted using BPE-ECL to detect bacterial concentration. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eD, the ECL signal values of three actual samples at different concentrations of \u003cem\u003eE. coli\u003c/em\u003e O157:H7 indicate that the sensor has high precision and high sensitivity. These results indicate that this method is expected to be used for the quantitative detection of \u003cem\u003eE. coli\u003c/em\u003e O157:H7 in actual food samples and has broad application prospects in related fields.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of different bacteria sensors.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMethod\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSystem\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDetection range\u003c/p\u003e\u003cp\u003e(CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eDetection limit\u003c/p\u003e\u003cp\u003e(CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLFIA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDA functionalized AuNPs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u003csup\u003e2\u003c/sup\u003e~10\u003csup\u003e7\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e10\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eELISA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDA-based FeCoMOF/Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoenzymes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u003csup\u003e1\u003c/sup\u003e~10\u003csup\u003e8\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLC-based\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFabric mesh-anchored liquid crystal platform utilizing the cationic surfactant cetyltrimethylammonium bromide (CTAB)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u003csup\u003e1\u003c/sup\u003e~10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFluorescent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCombine CDs with covalent organic frameworks (COFs)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u0026thinsp;~\u0026thinsp;10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWhole-cell imprinted microarray platform\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u0026thinsp;~\u0026thinsp;10\u003csup\u003e7\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBPE-ECL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAu@MOF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\u0026thinsp;~\u0026thinsp;10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eThis article\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study developed an ECL sensor by integrating the Au@MOF structure with a bacterial molecularly imprinted BPE for the detection of \u003cem\u003eE. coli\u003c/em\u003e O157:H7. The sensor was fabricated by electrochemically polymerizing PDA and \u003cem\u003eE. coli\u003c/em\u003e O157:H7 on the cathode of the BPE, thereby forming highly specific recognition sites. The MOF structure can catalyze redox reactions, and the further synthesized Au@MOF nanocomposites, after modification with SH-Apt, can specifically recognize the target bacteria. Then, the Au@MOF can catalyze the reduction reaction of the TMB/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e system. Due to the electro-neutrality principle of the BPE, the oxidation reaction of the [Ru(bpy)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e/TPA system on the anode generates a distinct ECL signal. The sensor has a wide linear detection range (1-10\u003csup\u003e6\u003c/sup\u003e CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and an ultralow detection limit (1 CFU mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), demonstrating excellent analytical performance. Additionally, the sensor shows high selectivity for \u003cem\u003eE. coli\u003c/em\u003e O157:H7 and can effectively distinguish it from \u003cem\u003eSalmonella\u003c/em\u003e and \u003cem\u003eS.\u003c/em\u003e aureus. The combination of bacterial molecularly imprinted technology with Au@MOF for ECL detection provides a promising platform for rapid and accurate pathogen detection.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e Yunlong Liu: Writing \u0026ndash; review \u0026amp; editing. Panpan Liu: Formal analysis, Writing \u0026ndash; review \u0026amp; editing. Mengjuan Li: Validation, Writing \u0026ndash; review \u0026amp; editing. Fengyang Wang: Validation, Writing \u0026ndash; review \u0026amp; editing. Yusong Wan, Yan Qi and Lei Ji: Validation, Writing \u0026ndash; review \u0026amp; editing. Xiaohui Xiong: Formal analysis, Conceptualization, Methodology, Funding acquisition, Project administration. Yuanjian Liu: Funding acquisition, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e This work was financially supported by the Postgraduate Research and Practice Innovation Programme Projects of Jiangsu (No. SJCX24_0497).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003eAll data provided by this article are available on request from the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e This study did not involve human or animal subjects, and thus, no ethical approval was required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLi JT, Yang XL, Li QL, Yang DZ, Hu QF, Zhong ZT, Yang YL (2024) Sensitive Colorimetric Aptasensor for Multiple Foodborne Pathogens Detection Based on PCN-Mo Peroxidase-like Activity. 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Firstly, dopamine (DA) was mixed with E. coli O157:H7 through an electropolymerization process to form polymer film on the BPE cathode. After bacteria removal, the bacterial molecularly imprinted polydopamine (PDA) film remained on the cathode, exhibiting high specificity for bacterial recognition and binding. Secondly, the E. coli O157:H7 aptamer was modified to the Au@MOF surface by Au-SH covalent bonds. Then, E. coli O157:H7 was present at the cathode, through the specific binding of aptamer to E. coli O157:H7, Au@MOF was assembled to the electrode surface. Finally, 3,3′,5,5′-tetramethylbenzidine/H2O2 (TMB/H2O2) solution was added to the cathode. The Au@MOF exhibited peroxidase-like activity and could catalyze the reduction reaction of TMB/H2O2 system. Due to the electrical neutrality principle of the BPE, the oxidation reaction of [Ru(bpy)3]2+/tripropylamine ([Ru(bpy)3]2+/TPA) system on the anode, generating a distinct Electrochemiluminescence (ECL) signal. The sensor detected E. coli O157:H7 within a concentration range of 1 to 106 CFU mL-1, with a detection limit of 1 CFU mL-1, demonstrating high selectivity and sensitivity. This BPE platform, integrating molecular imprinting and Au@MOF-assisted oxygen reduction, shows significant potential for bacteria detection in various applications.","manuscriptTitle":"Detection of E. coli O157:H7 using bacterial molecularly imprinted bipolar electrode and Au@metal-organic framework","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-05 19:08:01","doi":"10.21203/rs.3.rs-7210225/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b533867a-af4e-4e7e-a918-4f4856ddd507","owner":[],"postedDate":"August 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-08-08T05:31:39+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-05 19:08:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7210225","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7210225","identity":"rs-7210225","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}