Síntese e caracterização de nanopartículas de prata e determinação da sua atividade antimicrobiana

Abstract

One of modern society’s main issues is the search for new ways to combat pathogenic bacterias responsible for a range of diseases. These bacteria are highly mutable and increasingly resistant to antibiotics, that are increasingly limited and difficult and slow to develop. In this work, knowing the existence of silver's antimicrobial properties, searched to synthesize, characterize and evaluate the effects of silver nanoparticles (Ag-NPs) on bacterial cultures aiming at applications mainly on polymeric films / blends and surfaces. The synthesis of Ag-NPs was performed using the chemical reduction method using silver nitrate (AgNO3) as precursor salt, sodium borohydride (NaBH4) as reducing salt and carboxymethylcellulose (CMC) as stabilizing agent. To determine the optimal concentrations of each reagent, were used the factorial design and response surface obtained after UV-vis spectroscopy of each sample. UV-Vis spectrometry and electron transmission microscopy (TEM) were used to characterize Ag-NPs optimally synthesized (CMC: 0,07% (m/v); NaBH4: 3,5 x 10-4 mol L-1; e AgNO3: 3,5 x 10 -4 mol L-1) by obtaining surface plasmon band (BPS) scans, dispersion and Ag-NPs’s diameter - 2.01 ± 0.54 nm. In microbiological tests, diffusion plaque test was used to determine qualitative elements (evidence of antibacterial effect and effectiveness) and microdilution plaque and spot test for quantitative elements (determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) respectively). The concentrations obtained were: Clostridium perfringens: MIC = 0.0149 μg mL-1, MBC = 0.0149 μg mL- 1; Staphylococcus aureus: MIC = 0.0299 μg mL-1, MBC = 0.0299 μg mL-1; Escherichia coli: MIC = 0.0149 μg mL-1, MBC = 0.0299 μg mL-1; Pseudomonas aeruginosa: MIC = 0.0299 μg mL-1, MBC = 0.0299 μg mL-1. These results demonstrated the effects of Ag-NPs against the effects with different macromolecular complexes on the cell wall, with a high potential for application and future work, as Ag-NPs were not only able to inhibit / remove C. perfringens , E. coli, and S. aureus in similars ampicillin’s concentracions (an antibiotic commonly used without microbiological control), but were also used against P. aeruginosa - an ampicillin resistant bacterium.