Natural quercetin-derived carbon nanodots for dual antibacterial and anti-inflammatory therapy against bacterial infections

Bacterial infections and the associated inflammatory responses present significant challenges to public health, underscoring the need for innovative therapeutic strategies. In this study, novel carbon dots (QA-CDs) derived from quercetin (QU) and 4-aminophenol (4-AP) were synthesized using a one-step hydrothermal method. This approach merges the antimicrobial properties of phenolic compounds with the multifunctional advantages of carbon-based nanomaterials. The resulting QA-CDs exhibited a spherical morphology with an average diameter of 3.23 nm and abundant surface functional groups. In vitro antimicrobial assays demonstrated that QA-CDs effectively inhibited the growth of E. coli and S. aureus, with minimum bactericidal concentrations (MBCs) of 100 μg/mL and 25 μg/mL, respectively. Mechanistic studies revealed that QA-CDs disrupted bacterial membrane integrity, induced nucleic acid leakage, and exhibited strong reactive oxygen species (ROS) scavenging activity. Notably, QA-CDs significantly downregulated the mRNA expression of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β, iNOS, and TGF-β1) while upregulating the anti-inflammatory cytokine IL-10 in lipopolysaccharide (LPS)-induced RAW264.7 cells. In vivo studies using murine models of peritonitis and pneumonia showed that QA-CDs completely eradicated MRSA in infected tissues and reduced TNF-α and IL-1β levels in organ lavage fluids, confirming their dual antibacterial and anti-inflammatory effects. With excellent biocompatibility (hemolysis rate <5 % and no significant organ toxicity) and broad-spectrum antimicrobial activity, QA-CDs represent a promising nanotherapeutic strategy for treating bacterial infections and associated inflammatory disorders.