High Binding Density Coatings for Biomolecules on Plasmonic Gratings and Their Sensing Applications

The COVID-19 pandemic has exposed a critical need for advances in high-throughput and high-resolution epidemiological testing devices with both high clinical sensitivity and specificity. Curbing the rapid spread of emerging diseases requires detection of biomarkers for disease at extremely sparse levels from body fluids. Sample preprocessing prior to detection is often used to increase the amount of biomarker in a patient sample to detectable limits, including polymerase chain reaction (PCR). Alternatively, the sensor might be designed to amplify intrinsic signal, improving the signal generated by sparsely distributed molecules without sample preprocessing. Identifying more stable and highly dense binding surfaces is critical to improving shelf-life, reducing binding protocol complexity, and expanding to a wider range of applications. Polystyrene well plates after exposure to gamma radiation are commonly used for high-density binding substrates. Herein, we present the development of a stable, ultra-thin polystyrene film on plasmonic gratings and demonstrate bioconjugation comparable to commercially available well plates without the need for surface activation (e.g., nuclear irradiation). Testing using Rhodamine Red X-labeled antibody bound to the plasmonic gratings showed a factor of 63.8 times brighter fluorescence signal than commercial Nunc MaxiSorp® plates using the same concentration of biomolecule.