Construction of Chitosan Carbon Dot/Quercetin Composite nanosystem with Enhanced Antioxidant Properties

In this study, a novel chitosan carbon dot/quercetin (CS-CDs/Que) composite nanosystem was constructed. Utilizing the abundant carbon, nitrogen, hydroxyl, and amino functional groups in the molecular structure of chitosan, carbonization, molecular polycondensation, and surface passivation were achieved through a hydrothermal method, ultimately forming chitosan carbon quantum dot carriers (CS-CDs) with an average size of 6.27 nm. Quercetin (Que) was then loaded onto these carriers to construct the composite nanosystem. Structural characterization of the composite nanosystem was conducted using techniques such as transmission electron microscopy and infrared spectroscopy, confirming the successful hybridization of the nanocomposites. Notably, compared with Que alone, the CS-CDs/Que composite nanosystem exhibit significantly enhanced antioxidant capacity under the same mass concentration. The scavenging rates of CS-CDs/Que for DPPH and ABTS can reach 92% and 62%, respectively; their chelating ability for ferrous ions is also much stronger than that of Que. Furthermore, CS-CDs/Que can effectively scavenge superoxide anion free radicals and hydroxyl free radicals. When the concentration of CS-CDs/Que is 15 µg mL −1 , it achieved a 100% scavenging rate for hydroxyl radicals. Overall, the prepared CS-CDs/Que composite nanosystem show excellent antioxidant activity, providing new insights for the development of novel antioxidants.