Label -free measuring biomolecular interactions using plasmonic metasurfaces with dual bands based on surface lattice resonances in the mid-infrared range

Abstract

Mid-infrared plasmonic metasurfaces are remarkable platforms for chemical-specific detection and dynamic monitoring of biomolecules. This study uses surface-enhanced infrared absorption (SEIRA) spectroscopy by applying plasmonic metasurfaces for label-free and real-time monitoring of biomolecular interactions. SEIRA devices based on geometric combinations of two types of square arrays with different Au microdots require the use of new dual-resonant plasmonic metasurfaces. Resonant matching between the plasmonic and molecular vibrational modes can be realized through the controlled microdot dimensions and periodicity of the array. Plasmonic surface lattice resonances contribute to this optical tuning, enabling simultaneous observations of SEIRA-enhanced methyl and amide bands. The electric fields on mixed arrays were strongly confined to approximately 100 nm, enabling high SEIRA performance and single molecule detection. Moreover, the SEIRA device no longer needed in-plane polarization control of IR light, enhancing sensing detection’s robustness and stability. Finally, the in situ real-time monitoring of biomolecular interactions between protein A and immunoglobulin, which provides remarkable changes in the intensity and vibrational features of SEIRA absorbance, is reported. Dynamic SEIRA measurements using molecular vibrations as self-biomarkers helped in identifying the kinetic parameters required for important affinity metrics of biomolecular interactions.