Antibacterial activity modulation of silver nanoparticles prepared by green synthesis with aqueous extracts from different organs of native Argentinean trees

Abstract

Aqueous extracts of the leaves, branches, and barks of Schinopsis lorenzii (SL) and Sarconphalus mistol (SM), were employed in the green synthesis of silver nanoparticles (AgNPs). The characterization of the nanocomposites by UV-vis and ATR-FTIR absorption spectroscopies confirmed the presence of phenolic functional groups, which have the potential to act as reductants of silver ions (Ag+). The formation of polymorphic AgNPs was evidenced by dynamic light scattering measurements, with average diameters between 70 and 184 nm and markedly negative zeta potential values. The antimicrobial efficacy was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The nanocomposites showed the most pronounced inhibitory effect against the Gram-positive S. aureus. The decrease in the minimal inhibitory concentration (MIC) for all strains with an increase in both the size/charge ratio and the Ag+ release capability of the nanocomposites provides evidence that the nature of the aqueous extract of these native trees used in the biosynthesis of AgNPs is the determining factor in the selective antimicrobial activity achieved. Furthermore, the destabilization of the bacterial membrane also increased with the attachment of the AgNPs to the bacterial surface, as indicated by the changes in the zeta potential values.In conclusion, this study demonstrates that the nature of the aqueous extract used in the biosynthesis of AgNPs can provide new antimicrobial formulations with selective microbicidal activity.