Nanopartículas de prata (AgNPs): síntese verde, utilizando extrato da borra de café como agente redutor, caracterização e aplicação

Abstract

The conventional synthesis of silver nanoparticles (AgNPs) often relies on toxic chemicals, motivating the development of environmentally friendly alternatives based on green chemistry principles. This study aimed to synthesize AgNPs through a green route and incorporate them into bacterial cellulose (BC) membranes to develop a biomaterial with antimicrobial properties. AgNPs were synthesized using aqueous and ethanolic coffee grounds extracts as reducing and stabilizing agents, while sodium citrate was employed as a capping agent. BC membranes were produced by cultivating a Kombucha starter culture in a natural medium, followed by inoculation into a synthetic medium for film production. After purification, the membranes were subjected to two AgNP impregnation methods. UV–Vis spectroscopy confirmed the formation of AgNPs, with characteristic surface plasmon resonance bands between 420 and 450 nm. The nanoparticles exhibited low polydispersity, with estimated sizes ranging from 85 to 90 nm based on full width at half maximum (FWHM) calculations. Physical characterization of the BC membranes revealed high water retention capacity, with an 89.6% mass loss after drying and a dry grammage of approximately 307 g/m², indicating the formation of a robust barrier structure. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) confirmed the successful incorporation of silver into the cellulose network. Elution assays demonstrated the stability of the composite material, showing no significant release of AgNPs into a buffer solution over a 24-hour period. Antimicrobial activity, evaluated by the disk diffusion method, revealed strong inhibitory effects against both Gram-positive and Gram-negative bacteria, producing inhibition zones comparable to those of commercial antibiotics. These results demonstrate that bacterial cellulose membranes incorporated with sustainably synthesized silver nanoparticles constitute a stable composite material with significant bactericidal activity. Therefore, this biomaterial shows potential for future applications as a primary wound dressing. Further in vitro and in vivo studies are required to assess its cytotoxicity and confirm its safety for biomedical applications.