دانلود رایگان مقاله فعالیت هم افزایی ضد باکتری نانوکامپوزیت پگیلیتد نقاط کوانتومی

abstract

 The emergence of antibiotic-resistant bacteria is a major threat to world-wide public health. Functionalized nanoparticles could offer novel strategies in this post-antibiotic era. In this study, we developed nanocomposites of silver nanoparticles decorated with graphene quantum dots (Ag-GQDs) using pulsed laser synthesis. The nanocomposites were PEGylated, which increases their biocompatibility and solubility in aqueous solutions. The HR-TEM micrographs of bare GQDs show that their size is in the range of 1.6–4 nm, and the lattice spacing is 0.214 nm, which corresponds to the (1 0 0) lattice fringes of graphene. The antibacterial activity of Ag-GQDs was evaluated and compared to that of bare GQDs and commercial silver nanoparticles (Ag-NPs) against both Gram-negative and Gram-positive bacteria, using Pseudomonas aeruginosa and Staphylococcus aureus as model bacteria, respectively. Concentration values of 25 and 50 g/mL are required for Ag-GQDs to inhibit the growth of S. aureus and P. aeruginosa bacteria, respectively. The fractional inhibitory concentration (FIC) index is below 0.5 indicating that there is a synergistic effect between Ag-NPs and GQDs. Kirby–Bauer tests showed that Ag-GQDs inhibit P. aeruginosa and S. aureus, in contrast to bare GQDs and Ag-NPs alone. Cell viability of normal mammalian cells treated with Ag-GQDs showed that cell viability is maintained at 100% for cells incubated with Ag-GQDs. The decoration of Ag-NPs with GQDs minimizes their cytotoxicity in mammalian cells and increases their biocompatibility. Ag-GQDs have potential applications in the fabrication of antibacterial coatings, self-sterile textiles, and personal care products.

4. Conclusions

We successfully synthesized biocompatible nanocomposites of Ag-GQDs consisting of Ag-NPs decorated with GQDs on their surface and functionalized with PEG. The Ag-GQDs showed enhanced antibacterial activity against P. aeruginosa and S. aureus bacteria, which are used as Gram-negative and Gram-positive model bacteria, respectively. The results showed that the decoration of Ag-NPs with GQDs fosters a synergistic effect and reduces dramatically the concentrations required to inhibit both bacterial strains, which are commonly isolated from microbial infections in wounds. The effective antibacterial concentrations of Ag-GQDs did not affect the viability of human and animal cells, which suggest that they are biocompatible and ecofriendly. These results also suggest that Ag-GQDs nanocomposites may be applied as antibacterial material, such as in: antibiotics, coating of surgical instrumentation, wound dressing textiles, disinfectants, antiseptic and detergents. Further studies are necessary in order to elucidate the exact mechanism(s) of Ag-GQDs that induce bacterial cytotoxicity.