A portable intelligent hydrogel platform for multicolor visual detection of HAase.

Hyaluronidase (HAase) is an important endoglycosidase involved in numerous physiological and pathological processes, such as apoptosis, senescence, and cancer progression. Simple, convenient, and sensitive detection of HAase is important for clinical diagnosis. Herein, an easy-to-operate multicolor visual sensing strategy was developed for HAase determination. The proposed sensor was composed of an enzyme-responsive hydrogel and a nanochromogenic system (gold nanobipyramids (AuNBPs)). The enzyme-responsive hydrogel, formed by polyethyleneimine-hyaluronic acid (PEI-HA), was specifically hydrolyzed with HAase, leading to the release of platinum nanoparticles (PtNPs). Subsequently, PtNPs catalyzed the mixed system of 3,3',5,5'-tetramethylbenzidine (TMB) and H 2 O 2 to produce TMB 2+ under acidic conditions. Then, TMB 2+ effectively etched the AuNBPs and resulted in morphological changes in the AuNBPs, accompanied by a blueshift in the localized surface plasmon resonance peak and vibrant colors. Therefore, HAase can be semiquantitatively determined by directly observing the color change of AuNBPs with the naked eye. On the basis of this, the method has a linear detection range of HAase concentrations between 0.6 and 40 U/mL, with a detection limit of 0.3 U/mL. In addition, our designed multicolor biosensor successfully detected the concentration of HAase in human serum samples. The results showed no obvious difference between this method and enzyme-linked immunosorbent assay, indicating the good accuracy and usability of the suggested method.