Enzyme cascade-induced optical sensing of hyaluronidase using an ultraviolet-modified liquid crystal interface

H yaluronidase (HAase) is a clinically significant enzyme involved in tumor progression, extracellular matrix remodeling, and inflammation. Hence, HAase is an important biomarker for disease diagnostics. Here, a label-free, pH-responsive biosensor using ultraviolet (UV)-treated liquid crystals (LCs) for HAase detection is presented. The sensor utilizes a cascade enzymatic reaction where HAase hydrolyzes hyaluronic acid (HA) into oligosaccharides, which are sequentially degraded by β-glucuronidase, chitosanase, and amine oxidase into glucosaminic acid, hydrogen peroxide, and protons (H⁺). This results in a significant decrease in pH. The pH change alters the protonation state of the 4-cyano-4'-biphenylcarboxylic acid UV-induced product of 4-cyano-4'-pentylbiphenyl, triggering a distinct optical reorientation of the LC at the aqueous interface. Reorientation is evident as a dark-to-bright transition in polarized optical microscopy. The sensor is highly sensitive with a detection limit of 0.0018 U/mL and a linear detection range from 0.3 to 40 U/mL. The sensor also demonstrates excellent selectivity and can detect HAase in dilute human serum and urine samples, highlighting its potential as a practical diagnostic platform.