Abstract
Increasing drugs and antibiotic resistance against pathogenic bacteria create the necessity to explore novel biocompatible antibacterial materials. This study investigated the antibacterial effect of carbon dot (C-dot) against E. coli and suggested an effective synergistic dose of tetracycline with C-dot, using mathematical modeling of antibacterial data. Colony count and growth curve studies clearly show an enhanced antibacterial activity against E. coli synergistically treated with C-dot and tetracycline, even at a concentration ten times lower than the minimum inhibitory concentration (MIC). The Richards model-fit of growth curve clearly showed an increase in doubling time, reduction in growth rate, and early stationary phase in the synergistic treatment with 42% reduction in the growth rate (μm) compared to the control. Morphological studies of E. coli synergistically treated with C-dot + tetracycline showed cell damage and deposition of C-dots on the bacterial cell membrane in scanning electron microscopy imaging. We further validated the topological changes, cell surface roughness, and significant changes in the height profile (ΔZ) with the control and treated E. coli cells viewed under an atomic force microscope. We confirmed that the effective antibacterial doses of C-dot and tetracycline were much lower than the MIC in a synergistic treatment.
Highlights
Several studies suggest that nanoparticles (NPs) can be an excellent replacement to antibiotics and effective drug carriers and are suitable for multifunctional designs with their broad-spectrum antibacterial properties, considering the availability of various functional groups (Mühling et al, 2009; Pelgrift and Friedman, 2013; Beyth et al, 2015)
We have explored the antibacterial efficacy of carbon dot (C-dot)
The C-dot–treated cells showed a decrease in the number of colonies compared to the control plate, where more than 50% of the colonies decreased at 8.0 μg/mL C-dot concentration (Figure 1B, Supplementary Figure S3 and Supplementary Table S2)
Summary
Several studies suggest that nanoparticles (NPs) can be an excellent replacement to antibiotics and effective drug carriers and are suitable for multifunctional designs with their broad-spectrum antibacterial properties, considering the availability of various functional groups (Mühling et al, 2009; Pelgrift and Friedman, 2013; Beyth et al, 2015). C-dot possesses photo excited state properties and redox processes similar to conventional nanoscale semiconductors (Rocha et al, 2002; Hu et al, 2015; Jelinek, 2017; Righetto et al, 2017), which initiate the efficient photoinduced charge separation This process allows the formation of radical anions and cations (Cao et al, 2013; Fernando et al, 2015; LeCroy et al, 2016). Due to their photoinduced redox potential, C-dots are excellent candidates functioning as antibacterial agents and are effective against bacterial cells, under normal visible/ natural light illumination without giving an excess dose of the photon (Lim et al, 2015; Meziani et al, 2016). An excess amount of photons triggers C-dot–dependent photodamage of tetracycline and other similar antibiotics (López-Peñalver et al, 2010; Nagamine et al, 2020; Semeraro et al, 2020; Xu et al, 2020; Liu et al, 2021)
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