SERS-based hydrogel sensors for pH and enzymatic substrates

A sensing hydrogel for potential implantation was demonstrated using pH-sensitive surface-enhanced Raman scattering (SERS) reporters. The gold nanoparticle-based pH probes were encapsulated within polyelectrolyte multilayer microcapsules and embedded in a hydrogel matrix. These sensors were fully characterized for pH sensitivity and reproducibility. They were further combined with glucose oxidase (co-encapsulated with the nanoparticles) to generate a glucose-sensitive response, and the Raman signals of the system were recorded in the physiological glucose range (0-400 mg/dL). The results demonstrate SERS based sensing via pH sensitive Raman molecule modified gold nanoparticles (MBA-AuNPs) encapsulated within hydrogels. Further, upon incorporation of GOx, a pH decrease was observed due to glucose oxidization. However, the diffusion-reaction system will need to be better balanced to achieve a more glucose-proportional change for steady-state pH.