Síntese e caracterização de nanopartículas de prata estabilizadas com goma do cajueiro: atividade catalítica, antibacteriana e avaliação da toxicidade

Abstract

Across the globe, large amounts of effluent are disposed off daily in natural waters. Among the main residues generated are dyes, toxic compounds with difficult degradation, which can cause serious problems to fauna and flora due to the mutagenic nature of their con- stituents. Nanoparticles stabilized with natural products and their derivatives, are an alternative in the treatment of these effluents due to their physical and chemical prop- erties, and can act as support material in the transformation of several pollutants. In this work, silver nanoparticles (AgNPs) stabilized with the polysaccharides cashew gum (GC-AgNPs), acetylated cashew gum (GCA-AgNPs) and carboxymethylated cashew gum (GCC-AgNPs) were synthesized for use as catalysts of the Sodium borohydride (N aBH4) the reduction reaction of Congo red, a toxic and carcinogenic dye, widely used in different industries. The AgNPs were characterized by uv-visible spectroscopy, dynamic scattering of light, zeta potential, Fourier transform infrared spectroscopy, atomic force microscopy and nanoparticle tracking analysis. The data indicated the success of the synthesis and it was possible to verify which parameters were determinant for the size and stability of the AgNPs. The nanoparticles showed efficient catalysts in the degradation of the Congo red, considerably reducing the reaction time to only 25 minutes. The antimicrobial po- tential of the particles was also evaluated, indicating that GCA-AgNPs and GCC-AgNPs presented bacteriostatic effect against Staphylococcus aureus ATCC 29213, Staphylococ- cus aureus MRSA 43300 and Escherichia coli ATCC 25922. In analyzing the toxicity of the substances used in this work through the Galleria mellonella model, GC-AgNPs and GCC-AgNPs showed a percentage survival of 93.7 % of the population of larvae tested and GCA-AgNPs presented 81.2 %, not being considered toxic. Congo red was toxic, in- ducing the death of 62.5 % of the larvae tested, while the residue from its degradation induced the death of only 6.7 % of the population, indicating a decrease in the toxicity of the system after the reduction reaction catalyzed by AgNPs.