Mid-infrared Laser Spectroscopy for Ultra-Low Concentration Protein in Quartz Hollow Waveguide

Protein analysis is of significant importance in the biomedical field. Mid-infrared absorption spectroscopy offers advantages such as non-invasiveness, label-free detection, and real-time monitoring, making it highly beneficial for studying protein concentrations and conformational changes. However, current mid-infrared absorption spectroscopy systems for protein analysis face challenges like complex equipment, high costs, and low sensitivity, which greatly limit research capabilities. In this work, we present a method using a quartz hollow waveguide as a microfluidic reaction vessel, combined with biotin-functionalized gold nanoparticle-based materials that provide Surface-enhanced infrared absorption (SEIRA) effects and streptavidin capture capabilities. This approach achieves ultra-low detection limits for streptavidin in the ng/mL range at the amide I and II bands. Additionally, the quartz hollow waveguide offers advantages such as low cost and compact size, showing great potential for integration into protein analysis spectrometers.