Biosynthesis of Silver Nanoparticles from Hybrid Polymer: Characterization, Approach from XRD and Investigation of
Expedito Lopes Fernandes Júnior1, Izabel Maria de Melo Amaral1, George Torres de Lima2
1Quality Control Core of Medicines and CorrelatesNCQMC, Department of Sciences, Federal University of PernambucoUFPE, Recife, State of Pernambuco CEP: 50670-901, Brazil.
Abstract:
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 CC 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 CO 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 (AgICSD 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.
