Lable-free optical miRNA detection using charged Au nanoparticles

Abstract A simple and efficient biosensing system was designed to measure miRNA-155 (miR-155) as a promising biomarker for early diagnosis of breast cancer. In this system, two different charged gold nanoparticles (Au NPs) were used: 1- negatively charged citrate-stabilized Au NP (Cit-Au NP) to immobilize the probe, 2- positively charged polyethylenimine-capped Au NP (PEI-Au NP) as an amplifier. The probe DNA covalently binds to the Cit-Au NP via Au–S bond in this system. A double-stranded probe DNA-miRNA is formed when miR-155 is introduced to the system. Then, PEI-Au NPs are added to the biosensing system to amplify surface plasmon resonance (SPR) changes in the absorption band of Au NPs. This amplification resulted in more stabilization of Au NPs in the presence of miR-155. On the contrary, in the absence of miR-155, Au NPs are aggregated due to the electrosteric interactions. This simple method achieves a detection limit of ~ 8 pM and a wide linear range from approximately 80 pM to 2 µM.