Photoelectrochemistry combines light excitation with electrochemical readout for lowering the bias voltage needed for performing electrochemical reactions. As a result, when used in biosensing, photoelectrochemical signal readout reduces the background signals, lowering the limit-of-detection of such biosensors. To enable photoelectrochemical (PEC) signal readout to be applied to point-of-need biosensing, we have taken a three tiered approach focused on improving the understanding of signal transduction in PEC Biosensing, developing label-free assays, and creating handheld readout platforms.

In this work, we developed a system using DNA as a nano-ruler to control the distance between plasmonic nanoparticles and PEC electrodes. This system was used to rationally-design PEC material systems for signal-on biosensing. Using this materials architecture, we developed a signal-on biosensor without target labeling for detecting DNA hybridization. This assay uses sequential DNA hybridization to generate a PEC signal. First, the DNA target is captured on probe-modified photoelectrodes. This is followed by hybridization of the unbound probes with DNA strands modified with plasmonic labels. The plasmonic label modulates the PEC signal, increasing the measured PEC current at low target concentrations. To enable biosensing at the point-of-need, we also developed a handheld PEC reader. The integration of plasmonic nanoparticles with PEC electrodes, label-free DNA assays, and handheld PEC readout paves the way toward bringing point-of-need PEC Biosensing.