Functionalization of Polydopamine on Fiber Optic-based Localized Surface Plasmon Resonance for Biosensor

This study features functionalization of polydopamine (PDA) on Au nanoparticles-coated fiber optics for biosensor applications, demonstrating both real-time (insitu) and at final stage (ex-situ) monitoring of the PDA polymerization with and without stirring. The measurement was set up in reflectance mode. Light from the halogen light source travels through the fiber optic, exciting a localized surface plasmon resonance (LSPR) of the Au nanoparticles along the sensing area in coupling to the evanescence field of the fiber optic. The reflected light spectrum is recorded and monitored by the spectrometer, and the evolution of the LSPR peak is tracked in real-time. As a result, the polymerization and deposition process of the PDA layer on the Au nanoparticle is observed to induce a redshift to the LSPR peak shift due to an increase in PDA thickness and refractive index. Moreover, the implementation of stirring during the PDA deposition process significantly accelerates the polymerization rate. Finally, the PDA functionalization was verified using bovine serum albumin (BSA) adsorption. The real-time binding process of BSA on the PDA layer is indicated by further LSPR peak redshift. The binding of BSA is irreversible upon solvent flush. These results showed that implementation of in-situ monitoring opens the possibility of monitoring nanoscale growth and activity in controlled environment that will benefit the development of sensitive, specific, and real-time biosensors for medical diagnostics, environmental monitoring, and food safety applications.