Thiol-linked hyaluronic acid-mediated encapsulation of RCR-stabilized gold nanoclusters for hyaluronidase sensing and cellular imaging.

Encapsulating peptide-stabilized gold nanoclusters (AuNCs) with thiolated hyaluronic acid (HA-SH) and selectively adding cysteine to the peptide sequence increased their photoluminescence. We found that peptide compositions with cysteine in the middle emitted the most. RCR-stabilized AuNCs can be purified using size-exclusion chromatography to characterize their optical characteristics, chemical composition, and possible structure. Our findings show that RCR-stabilized AuNCs have a unique chemical structure, microsecond photoluminescence lifetime, good quantum yield, and near-infrared emission peak. Due to Au-S bonding and electrostatic interactions, RCR-stabilized AuNCs were encapsulated with HA-SH to create nanocomposites. HA-SH-AuNCs had a longer emission peak, greater particle size, and better photostability than RCR-stabilized AuNCs. HAase break down HA in HA-SH-AuNCs, changing their structure and size. Thus, centrifugation makes it easier to separate HA-SH-AuNCs from HAase-digested ones. Similar to earlier sensors, HA-SH-AuNCs have great sensitivity and selectivity for HAase, with a linear range of 0.5-6.0 U/mL and a detection limit of 0.39 U/mL. They were useful for urine HAase determination, with spike recovery of 103 % to 107 %. HA-SH-AuNCs further served as a platform for targeted imaging of CD44 receptor-expressing cancer cells, demonstrating bioimaging and clinical diagnostic potential.