Mid-infrared plasmonic nanoantennas for protein structure detection

Engineered plasmonic nanoantennas with well-defined resonances in Mid-Infrared (Mid-IR) range enable unique possibilities for surface enhanced infrared absorption spectroscopy of biomolecular monolayers, including proteins, for detection, identification and analysis purposes through their distinct vibrational fingerprints. Proteins amide signatures contain vital information on their secondary structural properties which is important in understanding many incurable diseases such as type II diabetes and neurodegenerative disorders, including Alzheimer’s disease. Therefore introducing non-destructive label-free biosensors that enable structural analysis of proteins at their native states and in aqueous solution will provide unique advantageous in applications related to fundamental biology and diseases. In this work, we showed for the first time that plasmonic Mid-IR nanoantennas can sensitively differentiate the secondary structural compositions of protein monolayers both in dry and aqueous environments. Our experimental results with disease-related proteins using Mid-IR plasmonic nanorod antenna arrays demonstrate our platform as a powerful spectroscopic biosensor by detecting conformational variations in random structured monomeric monolayer and cross β-sheet structured fibrillated α-synuclein (α-Syn) protein as well as dominantly native β-sheet streptavidin protein.[1]