Fluorescent carbon dots with a high nitric oxide payload for effective antibacterial activity and bacterial imaging

Multidrug resistance of bacteria has led to the invalidation of traditional therapies using antibiotics and has formed a huge threat to human health. Therefore, promising antibacterial therapies are urgently demanded. Nitric oxide (NO) has attracted much attention in the field of antibacterial agents, and novel antibacterial materials based on NO are being developed rapidly. In this work, we first proposed a carbon dot (CDs)-based and NO-releasing platform for antibacterial application. Here, the chitosan-graft-poly(amidoamine) dendrimer (CPA) was used to synthesize fluorescent CDs via one-step hydrothermal carbonization, and CPA-CDs were successfully prepared, followed by loading NO with the formation of N-diazeniumdiolate (NONOate). The resultant CPA-CDs/NONOate displayed 3.5 times the NO content of the CPA copolymer. Due to their stable photoluminescence, the super-resolution bacterial imaging ability of CPA-CDs/NONOate was observed. Moreover, excellent in vitro and in vivo antibacterial effects were demonstrated against Pseudomonas aeruginosa, where bacterial viability and biofilm were significantly reduced. Further, in vivo assays proved the theranostic activity of CPA-CDs/NONOate in curing rats' wounds with serious bacterial infection. Importantly, these NO-releasing CDs possessed outstanding in vivo and in vitro biocompatibilities. This study provided a multifunctional strategy, providing a foundation for fast bacterial detection and precise antibacterial treatments.