SÍNTESE, CARACTERIZAÇÃO E ATIVIDADE ANTIBACTERIANA DE NANOPARTÍCULAS DE PRATA OBTIDAS COM A FRAÇÃO FENÓLICA DERIVADA DAS FOLHAS DE Gustavia augusta L

Abstract

Nanotechnology is a rapidly expanding interdisciplinary field with the potential to transform various sectors, especially healthcare. Among its advances, metallic nanoparticles stand out, widely investigated due to their antimicrobial properties. Among these, silver nanoparticles (AgNPs) stand out for presenting a broad antibacterial spectrum and a low probability of inducing microbial resistance. In this context, sustainable approaches, such as green synthesis mediated by plant extracts, have gained prominence for reducing environmental impacts and toxicological risks. Therefore, this study aimed to evaluate the potential of the plant species Gustavia augusta L. as a reducing and stabilizing agent in the green synthesis of AgNPs, as well as to investigate its physicochemical properties, antibacterial activity, and cell viability. For the synthesis, the phenolic fraction obtained from the plant's leaves was used as a reducing agent. A Central Composite Design (CCD) experimental design, associated with Response Surface Methodology (RSM), was applied to optimize synthesis conditions and evaluate the influence of experimental variables on the formation and activity of the nanoparticles. The AgNPs were characterized by UV-Vis spectrophotometry, dynamic light scattering, zeta potential, and transmission electron microscopy. Antibacterial activity was evaluated by the broth microdilution method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Staphylococcus aureus and Escherichia coli strains. Additionally, the cell viability of the nanoparticles was investigated in murine macrophage cells RAW 264.7. The formation of the AgNPs was confirmed by the color change of the dispersions and the presence of characteristic absorption bands between 400 and 500 nm in the UV-Vis spectrum. The average diameters ranged from 50.9 ± 11.8 to 245.3 ± 18.7 nm, with polydispersity indices between 0.216 ± 0.02 and 0.852 ± 0.13, and zeta potential values between –19.7 ± 2.0 and –42.1 ± 6.0 mV. The AgNPs showed relevant antibacterial activity, with MICs between 24.6 ± 4.4 and 123.2 ± 27.6 mg/L for S. aureus and between 8.8 ± 3.3 and 291.0 ± 137.2 mg/L for E. coli. The CBM values ranged from 160.5 to 1072.0 mg/L for S. aureus and from 30.0 to 544.0 mg/L for E. coli. Cell viability at 70% (V70) was estimated at 50 and 45 mg/L, respectively, for the optimum points determined by antibacterial activity against S. aureus and E. coli. It is concluded that G. augusta constitutes a promising source for the green synthesis of silver nanoparticles, resulting in nanomaterials with suitable physicochemical properties, significant antibacterial activity, and concentration-dependent cell viability. These findings contribute to the development of new antimicrobial agents and broaden the knowledge about the biotechnological potential of this plant species.