Terahertz polarization sensing of bovine serum albumin proteolysis on curved flexible metasurface

Abstract

Proteolysis is a key research field of biochemistry and plays an important role in biomedicine, the food industry, etc. Moreover, because many molecular collective vibration and rotation energy levels containing structural information of proteins, peptides, amino acids, and other molecules are located in the terahertz (THz) band, the THz spectroscopy can perform molecular-level characterization. Here, based on the traditional time-domain spectroscopy system, we propose a reflective polarization characterization method and use the resonance enhancement effect of the flexible chiral metasurface sensor to realize the sensing of bovine serum albumin (BSA) under the proteolysis of papain. Experimental results show that under different amounts of papain proteolysis, the THz polarization characteristic spectra of the BSA solution have significant differences. Its sensitivities of frequency shift, intensity, and polarization angle changes can reach the order of 106 GHz∙mL/mol, 106 dB∙mL/mol, and 106 °∙mL/mol, respectively, and the concentration detection accuracy of papain reaches in the order of nmol/mL. This work demonstrates a new THz label-free, on-chip, wearable, and microfluidic sensing method and device for protein detection.