In situ synthesis of high swell ratio polyacrylic acid/silver nanocomposite hydrogels and their antimicrobial properties.

Silver nanocomposites embedded within a polymer matrix have attracted attention in recent years. Ionic polymer hydrogels comprise networks of chemically or physically cross-linked polymers that swell considerably in an appropriate solvent. In this study, we used a solution of the carboxylic monomer acrylic acid and silver nitrate to prepare nanocomposite hydrogels through ultraviolet (UV)-light irradiation. Silver-impregnated biomaterial composed of acrylic acid contains only a monomer and no cross-linker. The formation of hydrogels and reduction of silver nanoparticles were affected by the preparation parameters, that is, the monomer concentration and silver nitrate concentration. The morphology, structure, and size of the silver nanocomposite hydrogels were evaluated through field emission scanning electron microscopy and UV-visible absorption. The antimicrobial activity of the samples was tested against fourstandard strains Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli; and five clinical bacterial isolates Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumonia. The silver nanocomposite hydrogels exhibited an interconnected porous structure and could absorb 400 to 550g of deionized water per gram of dried hydrogel. Moreover, these hydrogels produced a strong antibacterial effect, which can be useful in developing new superabsorbent antimicrobial pharmaceutical products.

Biopolymer coated gold nanocrystals prepared using the green chemistry approach and their shape-dependent catalytic and surface-enhanced Raman scattering properties.

This study deals with the preparation of multi-shaped nanoscale gold crystals under synthetically simple, green, and efficient conditions using a seed-mediated growth approach in the presence of hyaluronic acid (HA). These highly biocompatible multi-shaped gold nanocrystals were examined to evaluate their catalytic and surface enhanced Raman scattering (SERS) properties. The results show that the size and shape of the nanocrystals are mainly correlated to the amount of seed, seed size, HA concentration, and reaction temperature. Gold seeds accelerate the reduction of the gold precursor to form gold nanocrystals using HA. The HA serves as a reducing agent and a growth template for the reduction of Au(III) and nanocrystal stabilization. The multi-shaped gold nanocrystals showed superior catalytic properties and higher SERS performance. The simple, green approach efficiently controls the nanocrystals and creates many opportunities for future applications.