Spermidine-capped carbon dots as potent antimicrobial nanomaterials against Escherichia coli

The food industry must prevent food contamination caused by pathogenic Escherichia coli, as they pose a severe public health threat globally, hence the need to explore new antimicrobial materials. In this paper, spermidine capped carbon dots (S-PCDs) were synthesized by hydrothermal reaction, and the antibacterial effects against E. coli and multi-drug resistant E. coli (MREC) was determined, so as to explore their potential application as antibacterial nanomaterials. The minimum inhibitory concentration values of S-PCDs against E. coli and MREC were 64 μg/mL and 128 μg/mL, respectively, showing strong antibacterial activity. The antibacterial zone was increased significantly with the increasing content of S-PCDs (p < 0.05). The results of bacteriostatic curve and bactericidal curve of S-PCDs on E. coli and MREC also showed that S-PCDs had a concentration-dependent inhibition on bacteria. In addition, the intrinsic antibacterial mechanism indicated that the antibacterial action of S-PCDs may involve cell membrane damage and reactive oxygen species production. During 30 days of exposure, S-PCDs showed persistent antibacterial effect against both E. coli and MREC without detectable resistance, especially without triggering secondary resistance in MREC. S-PCDs has potential application value in foodborne diseases caused by complex bacteria and even drug-resistant bacteria.