Multicolor Biosensor of Hyaluronidase by the Regulation of Enzyme-Like Catalytic Activity of Au Nanoclusters through Changes in the Aggregation State

The control of nanoparticle morphology can effectively change their properties. Adjusting the aggregation state of bovine serum albumin-coated gold nanoclusters (BSA-Au NCs) can regulate the enzyme-mimicking catalytic activity. Hyaluronic acid (HA) induces the aggregation of BSA-Au NCs, leading to the shielding of the catalytic active sites and a decrease in activity; this feature has been utilized to design a multicolor biosensor for hyaluronidase (HAase). The presence of HAase can hydrolyze the glycosidic bonds in HA, causing the aggregated BSA-Au NCs to disperse and express their catalytic activity, which in turn catalyzes the etching of Au nanobipyramids (Au-NBPs) in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB), resulting in a morphological transition from bipyramidal to ellipsoidal and spherical shapes, while the solution displays a variety of colors. Visual recognition of these multicolor changes establishes a relationship between the enzyme activity and color. Based on the controlled aggregation and dispersion of BSA-Au NCs and the etching of Au-NBPs, a simple multicolor HAase biosensor was designed. The proposed biosensor shows a linear response to HAase concentrations in the range of 5–80 U/mL, with clear color changes under optimized conditions. The limit of detection (LOD) of the sensor was determined to be 1.98 U/mL (LOD = 3s/k). This method successfully applies the changing of enzyme-mimicking catalytic activity nanoparticles for colorimetric analysis detection.