Carbon dot-based antimicrobial photosensitizer: Synthesis, characterization and antimicrobial performance against food borne pathogens

In this study, quasi-spherical carbon dots (CDs) with a white appearance were synthesized from acetate and zinc (Z). The size of the CDs was less than 10 nm and −11.4 mV zeta potential. At concentrations lower than 5 mg/mL, the Z-CDs showed no cytotoxicity in L929 fibroblasts. The antimicrobial activity of Z-CDs was dose-dependent on both Gram-positive (Listeria monocytogenes) and Gram-negative (Salmonella Typhimurium) bacteria in antimicrobial assays. Furthermore, observations from SEM imaging confirmed this activity. The photodynamic properties of the photosensitizer Z-CDs were examined with a focus on Z-CDs concentration and irradiation [i.e., time (0–120 min), temperature (4 and 25 °C), and LED lamps (360 and 420 nm wavelength)]. It was evident that L. monocytogenes was susceptible to photodynamic treatment at 25 °C when both wavelengths were utilized. The photodynamic properties of Z-CDs were influenced largely by temperature, followed by wavelength and Z-CDs concentration parameters. Remarkably, the bacterial cell membranes were significantly destroyed by Z-CDs and photodynamic treatments. These multifunctional Z-CDs are highly appealing candidates for food and biomedical applications owing to their favorable characteristics; such as low toxicity, photosensitizing properties, and appearance.