Carbon dots derived from metformin by electrochemical synthesis with broad-spectrum antibacterial properties.

Due to the advantages of good aqueous dispersion and biocompatibility, carbon dots (CDs) are promising candidates for a wide range of applications in the biological field. Notably, CDs derived from biosafe organic precursors will contribute both new types of CDs and new bioactivities. Herein, metformin (MET), a first-line drug for the treatment of type II diabetes, was selected as an organic precursor to fabricate a new type of CDs, namely, semi-carbonized MET (MCDs). These MCDs derived from MET possess a completely new antibacterial activity against Staphylococcus aureus ( SA ) and Escherichia coli ( E. coli ) compared with that of MET and achieve complete antibacterial activity at 200 μg mL -1 . The broad-spectrum antibacterial mechanism of MCDs involves two aspects. For the Gram-positive bacteria SA , MCDs mainly affect the transport of nutrients by adsorbing onto the surface of bacteria, thereby inhibiting bacterial growth. For the Gram-negative bacteria E. coli , MCDs can easily pass through their thin cell walls and stimulate the bacteria to produce excess ROS, eventually leading to the death of the bacteria. This work may open a new way for the future design and development of CDs prepared from biosafe organic precursors with specific functions.