Bio-functionalities of nitrogen based carbon dots from chitosan via in-situ incorporation with nano-copper

Recent researches were considerably interested in the biological performance of carbon dots as a unique member of carbon based-nanomaterials to find widely applicability in various purposes. This study investigates the direct incorporation of nano-copper within nitrogen based carbon quantum dots (N-CQDs) that were formerly ingrained from carboxy-methylated chitosan, via hydrothermal conditions without any reducing agent for biomedical applications. Copper was incorporated using three precursors including copper sulphate, copper nitrate, and copper acetate, yielding Cu(S)@N-CQDs, Cu(N)@N-CQDs, and Cu(C)@N-CQDs, respectively. Carboxy-methylated chitosan was firstly synthesized from chitosan via interaction with chloro-acetic acid. Non-doped N-CQDs exhibited an average particle size of 9.6 nm, while Cu(S)@N-CQDs, Cu(N)@N-CQDs, and Cu(C)@N-CQDs displayed increased sizes of 43.3 nm, 24.8 nm, and 40.7 nm, reflecting the distinct effects of precursor chemistry on particle growth. Cu doping significantly enhanced the biological functionalities of N-CQDs, including antimicrobial, antioxidant, and anti-inflammatory activities. Against Staphylococcus aureus, Cu(N)@N-CQDs achieved the highest bacterial reduction (89%), followed by Cu(C)@N-CQDs (87%) and Cu(S)@N-CQDs (84%), compared to 52% for undoped N-CQDs. Consistently, Cu(N)@N-CQDs also demonstrated superior antioxidant capacity (79.8% DPPH scavenging) and anti-inflammatory performance (68.1% cell viability), highlighting the pivotal role of precursor-dependent Cu incorporation in optimizing N-CQD bioactivity.