Near-infrared II fluorescent carbon dots for differential imaging of drug-resistant bacteria and dynamic monitoring of immune system defense against bacterial infection in vivo

In vivo fluorescence imaging allows the accurate acquisition of dynamic biological information, which plays a vital role in the early diagnosis and treatment of bacterial infectious diseases. Herein, a NIR-II-emitting CD-based nanoprobe (CyCDs) is synthesized using Cy7-CH3 as the carbon source and 3-hydroxytyramine hydrochloride as the surface passivator. Notably, the pi-conjugated system and rigid planar structure of the carbon source can broaden the wavelength range of absorption and emission. The presence of amino groups enables CyCDs with a positive zeta potential (+0.32 mV), which can facilitate the interactions between CyCDs and bacteria. Interestingly, CyCDs can only stain the cell wall of drug-resistant bacteria, while normal bacteria have a bright fluorescent signal over all of the cell. This phenomenon enables the identification of drug-resistant bacteria in vitro. Furthermore, CyCDs can be used to monitor the interaction between the immune system and infected bacteria in vivo and guide the timely usage of antibiotics