4 CONCLUSIONS
The swift proliferation of antibiotic resistance has necessitated the
development of antibacterial materials that afford excellent
antibacterial property while enjoying universal recognition akin to
antibiotics. In this study, a new type of CDs with photodynamic and
synergistic antibacterial effect is synthesized by means of a one-step
hydrothermal process, offering a new train of thought for combating
antibiotic resistance. Apart from the ROS intrinsically generated by the
CDs, evolution of singlet oxygen (1O2)
can also be triggered by the CDs under light irradiation, contributing
to a photoinduced synergistic bactericidal activity. The CDs possess
three advantages over the previously reported antibacterial materials.
By using citric acid and PEI as the precursor, first, the tiny
(~3 nm) yet uniform CDs can be produced in 2 h in a
single-step, one-pot fashion. The procedure may be achievable without
the need for a professional background. Second, the CDs afford enhanced
antibacterial effect with broad-spectrum effectiveness under
photoirradiation, depending upon their quantum yield that is tunable
with the molecular weight of PEI. Mechanistic insights into the
antibacterial effect reveal the CDs-induced disruption of bacterial
membrane and elevation of intracellular ROS level. Third, the CDs exert
minimal cytotoxicity even at a concentration of 100 mg/mL, pointing to a
high biocompatibility. This makes the CDs particularly useful for
applications in the fields of food packing, antibacterial coating of
medical devices and pharmaceutics. Given the synthetic accessibility and
wide availability of carbon sources, we suggest that the CDs be prepared
in a scalable and lower-cost way from waste organic materials. We also
hope that our findings will inspire more efforts on creation of
promising materials as potent antibacterial agents, which can combat
bacterial infections and biofilms while overcoming antibiotic
resistance.