A design for fast and effective screening of hyaluronidase inhibitor using gold nanoparticles

A hyaluronic acid-coated gold nanoparticle (HA-AuNPs) was synthesized and further employed for hyaluronidase (Hyal) assay and for screening effective inhibitors. The negatively charged hyaluronate on the surface of AuNP enhanced the solubility and stability of colloidal HA-AuNPs in aqueous solution. The HA-AuNPs in the solution possess a characteristic absorption band at 518 nm, whereas at the aggregation form, the band gradually red-shifts to 630 nm in various concentration of NaCl solution. The NaCl-induced red-shift absorption became steady when NaCl concentration reached 375 mM or higher concentration. In an enzymatic assay, Hyal promotes the hydrolysis of hyaluronate on AuNPs to produce more negatively charged HA oligomers, which can increase the surface shielding of AuNPs and to be released into solution to bind with sodium ion from NaCl. Both effects can largely prevent the aggregation of AuNPs. With this feature, inhibitors of Hyal can be effectively screened by monitoring the absorption change at 630 nm. Several effective inhibitors were found from a chemical library containing 2000 compounds. Thioguanine, harmine, and phenylbiguanide were selected for IC50 measurement using this newly designed method with values of 4.5, 13.3, and 28.7 μM, respectively. The same concept can be easily applied to the case of other polysaccharide degrading enzyme, such as chitosanase, condroitinase, haparinase, etc.