Polymer Optical Fiber-Based Plasmonic Biosensors for Medical Diagnostics ^†

In recent years, the classic geometries of sensors based on surface plasmon resonance (SPR) have been adapted for use in optical fibers (both extrinsic and intrinsic configurations), thus providing a simple approach to low-cost plasmonic sensing. For instance, polymer optical fibers (POFs) are particularly advantageous due to their excellent flexibility, ease of manipulation, great numerical aperture, large diameter and, last but not least, the fact that plastic can withstand smaller bend radii than glass. In bio-chemical applications, a very specific medium (receptor layer) for the selective binding of the considered analyte is deposited on a gold layer of the SPR platform. A simple and low-cost experimental setup, consisting of a halogen lamp and a spectrometer, can be arranged to measure the light spectrum transmitted through the SPR-POF sensors. Interesting applications have been devised and successfully implemented by exploiting these low-cost plasmonic POF platforms combined with different receptors, such as molecularly imprinted polymers (MIPs), chemical receptors, and bio-receptors (aptamers and antibodies). For example, by exploiting SPR in a D-shaped POF probe with different receptors, interesting results have been achieved in medical diagnostics for cancer bio-markers detection, the monitoring of antigens in celiac disease, L-nicotine detection, thrombin detection, and SARS-CoV-2 virus and pancreatic amylase detection. A survey of these medical applications is presented, highlighting the advantages and limitations of each application and revealing possible future implementations of the platform as a point-of-care device.