Silver nanoparticles (AgNPs) have recognized antimicrobial activity, but they are potentially harmful when obtained by traditional synthesis. In this context, biosynthesis offers a viable alternative using biological reducing agents. This work reports the biosynthesis of AgNPs using two materials: the biopolymer cashew gum (CG) and CG polymerized in situ with poly(methyl methacrylate) (PMMA). Fourier transform infrared (FTIR) spectroscopy confirmed the polymerization of PMMA/CG by the absence of C═C unsaturation. For both AgNPs, UV–vis absorption spectra confirmed their formation, as evidenced by the appearance of the surface plasmon resonance band. FTIR analysis of the AgNPs indicated that O–H and C═O groups participated in the silver reduction. The more significant reduction of these bands in AgNP-PMMA/CG suggests that the copolymer is an effective reducing agent for AgNP formation. These findings were corroborated by zeta potential measurements, which demonstrated greater colloidal stability for AgNP-PMMA/CG. XRD (X-ray diffractometry) peaks for both AgNPs were in agreement with the Miller indices (hkl) and indexed values (Ag─ICSD 22434), confirming a typical face-centered cubic structure. Through Rietveld refinement, a greater microstrain was observed for AgNP-CG (0.015) than for AgNP-PMMA/CG (0.01), despite a slight loss in the precision of the structural fit. AFM analysis of AgNP-PMMA/CG showed a more spherical shape and defined edges. In addition, the size distribution indicated a smaller size and less heterogeneity compared to AgNP-CG. Regarding antimicrobial activity, AgNP-PMMA/CG demonstrated bacteriostatic activity against all tested bacteria, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, while AgNP-CG showed activity only against Gram-negative strains. It also showed adequate cell viability in murine macrophages at all concentrations tested. In conclusion, the copolymer obtained was the most effective for the biosynthesis of AgNP-PMMA/CG. This material is considered promising due to its optimal structural organization, antimicrobial activity, biocompatibility, and more sustainable synthesis method.
Júnior et al. (Fri,) studied this question.