In the last decade, the need for faster, real-time and highly sensitive methods to characterize biomolecular interactions has yielded tremendous progress in the development of label-free biosensor techniques. The rapid progress in nanofabrication techniques and material science has propelled the development of novel nanostructures. Specifically, (bio)sensing is a critical field that nanostructured materials have impacted in recent years. Metallic nanostructures, such as nanohole arrays [NHAs) and crossed surface relief gratings (CSRGs), can couple incident light with the free electrons on the metallic surface, promoting a photonic phenomenon called surface plasmon resonance (SPR). SPR offers label-free sensing with high-sensitivity and reproducibility, providing the technique with noteworthy popularity as a commercial biomolecular analysis technique. However, commercial SPR systems involve complex optical setups that increase the cost and the size of the devices, making them impractical for portable point-of-care (POC) applications. NHAs and CSRGs offer all the advantages of the SPR technique, but with the possibility of collinear optics that reduce cost and allow for miniaturization.

In this dissertation, novel plasmonic nanostructures such as nanohole arrays and cross surface relief gratings were designed, investigated and characterized to evaluate their sensing and biosensing potential. Theoretical and simulation approaches were performed to evaluate the plasmonic effects of the fabrication parameters, such as size, material, and periodicity. The fabricated nanostructures were experimentally characterized and implemented on the SPR-based POC platforms presented in this thesis. The platforms are built with collinear optical setups consisting of off-the-shelf electronics and optical components. The applications demonstrated in this work include:​ 1] the development of a portable POC platform for the diagnosis of urinary tract infections (UTIs) using nanohole arrays and CSRGs — The platform allowed for the detection of pathogenic bacteria in clinically relevant concentrations in real-time analyte-analyte binding kinetic assays;​ 2] Variable pitch CSRGs evaluation for POC sensing applications;​ 3] Structural stability evaluation of flow-through NHAs;​ 4] A novel bioinspired template-stripped CSRGs (TS-CSRGs) demonstrated as a label-free surface-enhanced Raman scattering (SERS) substrates for biochemical sensing applications;​ 5] Study of diffusion kinetics of volatile organic compounds (VOC) on silicone-coated flow through NHAs for sensing applications. This dissertation demonstrates the potential of unique, miniaturized SPR-based POC platforms with high sensitivity and performance for several applications.