Catecholate Dye-Assisted Decoration of Ag on TiO₂ Nanoparticles for Detection of Cancer-Related MicroRNA Biomarkers on a Multiplexed Photoelectrochemical Platform

Photoelectrochemical (PEC) signal transduction has emerged as a powerful technique for ultrasensitive biosensing with a low background in complex media. However, it remains challenging to create PEC biosensors found on stable materials that are easily biofunctionalized. Herein, we report the development of a one-pot synthesis method for TiO2 nanoparticles (NPs) decorated with Ag NPs. In this nanomaterial synthesis process, TiO2 NPs are modified with hematoxylin (HTX) dye to achieve enhanced photoreduction and direct nucleation of Ag NPs. The resulting TiO2/HTX/Ag NP heterostructure showed significantly enhanced photocurrent generation, necessary for achieving high sensitivity in PEC biosensing, through the combined effects of plasmon resonance and photoelectron injection. TiO2/HTX/Ag NP is very easily biofunctionalized through thiol-metal complexation. This was taken as an advantage to create a multiplexing PEC microRNA sensor for the analysis of urine samples, which demonstrated a low limit of detection of 172 fM and a high dynamic range of 100 fM-100 nM, while showing a high degree of specificity.