RESUMO
Silver nanoparticles (AgNPs) have excellent antimicrobial properties, as they can inhibit multidrug-resistant (MDR) pathogens. Furthermore, bio-AgNPs have potential applications in medicine due to their low toxicity and high stability. Here, AgNPs were synthesized from the biomass of Aeromonas caviae isolated from a sediment sample and subsequently characterized. The UV-Vis spectra of AgNPs in aqueous medium peaked at 417 nm, matching their plasmon absorption. The X-ray diffraction analysis (XRD) pattern of AgNPs showed four peaks at 2θ values, corresponding to Ag diffraction faces. Absorption band peaks at 3420.16, 1635.54, and 1399.43 cm-1 were identified by Fourier-transform infrared spectroscopy (FTIR) analysis as belonging to functional groups of AgNP-associated biomolecules. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanoparticles are spherical and pseudospherical, with sizes of 15-25 nm. Agar well diffusion minimal inhibitory concentration (MIC) assays were used to assess the antibacterial activity of the nanoparticles against MDR pathogens. AgNPs exhibited antibacterial activity against MDR bacteria. Two groups of albino rats received intraperitoneal injections of AgNPs at 15 mg/kg or 30 mg/kg for 7 days. Blood, kidney, and liver samples were collected to investigate hematological, biochemical, and histopathological alterations. Administered AgNPs in rats fluctuated in liver and kidney function parameters. The ultrastructural impacts of AgNPs were more prominent at higher doses. The results proved the easy, fast, and efficient synthesis of AgNPs using A. caviae isolates and demonstrated the remarkable potential of these AgNPs as antibacterial agents. Nanotoxicological studies are required to identify the specific dose that balances optimal antibacterial activity with minimal toxicity to human health.
RESUMO
Background: Nanoparticles can be chemically, physically, or biologically synthesized. Biosynthesis of silver nanoparticles (AgNPs) utilizing microbes is a promising process due to the low toxicity and high stability of AgNPs. Here, AgNPs were fabricated by Gram-negative Raoultella planticola. Objectives: This study aimed to assess the ability of Raoultella planticola to produce nanoparticles (NPs) and evaluate their antibacterial potential against multidrug-resistant pathogens (MDR). Additionally, the study aimed to compare the antibacterial activity of biosynthesized nanoparticles to well-known conventional antibiotics Azithromycin and Tetracycline. Materials and Methods: AgNPs were characterized using visual observation, UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The TEM and SEM were used to determine the size and shape of the nanoparticles. The XRD data were recorded in the 2θ ranging from 20-80° to analyze the crystalline structure of nanoparticles. The antibacterial activity was detected using a 96-well microtiter plate. Results: The UV-vis absorption recorded from the 300 - 900 nm spectrum was well defined at 420 nm, and the XRD pattern was compatible with Braggs's reflection of the silver nanocrystals. FTIR showed absorbance bands corresponding to different functional groups. TEM and SEM images showed non-uniform spherical and AgNPs of 10-80 nm. XRD data confirmed that the resultant particles are AgNPs. The AgNPs showed effective activity against multi-drug resistant (MDR) Pseudomonas aeruginosa, Salmonella sp., Shigella sp., E. coli, Enterobacter sp., Staphylococcus aureus, and Bacillus cereus. The AgNPs demonstrated effectiveness in lower concentrations compared to broad-spectrum antibiotics. Conclusion: These data reveal that AgNP generated by R. planticola was more efficient against MDR microorganisms than commercial antibiotics. However, the cytotoxicity of these nanoparticles must be further studied.
