Solid-State Synthesized Hyperbranched Polyamides as Hosts for Antimicrobial Silver Nanoparticles

Abstract Silver nanoparticles (AgNPs) are versatile materials that offer interesting perspectives in biomedical, catalytic, and electronic fields, which certainly prompted research for sustainable synthetic routes with low cost since it meets both industrial requirements and minimize environmental damage. In fact, some hyperbranched polymers (HBPs) can be used to produce AgNPs through green processes resulting in colloids with great stability. HBPs are commonly synthesized by simple methods, supporting their large-scale production. At the present work, hyperbranched polyamide (HBPA) was used to prepare AgNPs within a hyperbranched network with narrow size distribution and average diameter of ca. 2–5 nm. Such AgNPs were synthesized by the chemical reduction method using NaBH4 and by auto-reduction (AR) process. Microbiological assays performed with the resulting hybrid hyperbranched HBP-AgNPs network (HBPENs) by AR presented antimicrobial activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Candida albicans with minimum inhibitory concentration (MIC) values ranging from 9.1 ± 0.2 to 56.6 ± 0.2 μg/ml. AgNPs synthesized using NaBH4 also showed good antimicrobial activity against the microorganisms tested. However, the MIC values were considerably higher than AgNPs by AR process, showing the AR method is a good alternative to obtain nanoparticles with better antimicrobial activity and smaller size.