Identification of a Pb(II) specific peptide and its application as a biorecognition unit for colorimetric detection of Pb(II) ions

Phage display technology employs a library of engineered filamentous M13 viruses infecting only bacteria. In this study, the genuine phage display selection technique was applied to identify a specific peptide selectively binding to one of the most toxic heavy metal ions, Pb(II). After three rounds of positive screenings against Pb(II) and the consecutive negative screenings against interfering metal ions (Al(III), Co(II), Fe(III), Ni(II) and Zn(II)), a final phage library with increased Pb(II) binding affinity was obtained. Enzyme Linked Immunosorbent Assay (ELISA) analyses confirmed the selective Pb(II) binding. 20 monoclonal phage plaques were randomly selected. Sequencing analyses revealed four consensus DNA sequences. Pb9 peptide (KASPYIT) showing the highest Pb(II) binding affinity was selected for detection studies. Pb9 was synthetically synthesized with additional 3 Cys units at C-terminal and coupled to 20 nm AuNPs through Au-S binding. A colorimetric Pb(II) detection system was validated using the engineered peptide-AuNP complex at a calculated LOD of around 11 nM (3σ/k, n=6) for the case study. The detection system was Pb(II) selective over various metal ions (Al, Ag, Au, Co, Cu, Cr, Fe, Ni, Mn and Zn). Target specific peptides can be further applied to develop simple, user friendly and cost-effective alternative detection tools which can be widened to environmental and healthcare research fields.