Identification of indium tin oxide nanoparticle-binding peptides via phage display and biopanning under various buffer conditions

Background: By recent advances in phage-display approaches, many oligopeptides exhibiting binding affinities for metal oxides have been identified. Indium tin oxide is one of the most widely used conductive oxides, because it has a large band gap of 3.7–4.0 eV. In recent years, there have been reports about several ITO-based biosensors. Development of an ITO binding interface for the clustering of sensor proteins without complex bioconjugates is required. Objective: In this article, we aimed to identify peptides that bind to indium tin oxide nanoparticles via different binding mechanisms. Methods: Indium tin oxide nanoparticles binding peptide ware selected using phage display and biopanning against indium tin oxide, under five different buffer conditions and these peptides characterized about binding affinity and specificity. Results: Three types of indium tin oxide nanoparticles-binding peptides were selected from 10 types of peptide candidates identified in phage display and biopanning. These included ITOBP8, which had an acidic isoelectric point, and was identified when a buffer containing guanidine was used, and ITOBP6 and ITOBP7, which contained a His-His-Lys sequence at their N-termini, and were identified when a highly concentrated phosphate elution buffer with a low ionic strength was used. Among these peptides, ITOBP6 exhibited the strongest indium tin oxide nanoparticles-binding affinity (dissociation constant, 585 nmol/L; amount of protein bound at saturation, 17.5 nmol/m 2-particles). Conclusion: These results indicate that peptides with specific binding properties can be obtained through careful selection of the buffer conditions in which the biopanning procedure is performed.