Surface-Enhanced Raman Scattering for Biosensor Probes

Abstract

In this work, several possible configurations of a glucose biosensor based on surface-enhanced Raman scattering (SERS) were investigated. The glucose biosensor is intended for measurements of blood glucose levels in diabetics. The SERS nanopatterns used in this work were fabricated on optical fiber end facets and microscope glass slides using nanosphere lithography. In this fabrication method, a densely packed monolayer of polymer microspheres is deposited onto a sample followed by deposition of a thin metal film. The SERS signals from nanopatterns on microscope glass slides were measured in a conventional Raman measurement setup. The measured signals were used to quantify the performance of the nanopatterns both by their ability to predict glucose concentrations through multivariate analysis and through their SERS enhancements. Analysis of the flat samples was used as a comparison for the performance of the sensor configurations under investigation. The suitability of each configuration for implementation in a biosensor was discussed. Simulations of the nanostructures under consideration were used to elucidate the electromagnetic interactions of light with the nanopatterns and to gain insight into the magnitude of the electric fields around the particle arrays. A promising and novel sensor configuration was reported, in which a ball-lensed fiber was used to couple light onto the nanopattern and collect the resulting SERS signal. Necessary improvements prior to implementation of the configuration in an actual glucose biosensor were discussed.