Bactericidal activity of spruce xylan hydrogel with in situ biosynthesized silver nanoparticles

Skin injuries, such as ulcers and wounds caused by first-degree burns, chronic inflammation, and other conditions, require effective bactericidal biomaterials to prevent complications that may lead to amputation, septicemia or even death. In this work, hydrogels based on spruce xylan (SX) with in situ grown silver nanoparticles (Ag-NPs) were developed, and their bactericidal activity was evaluated. Silver nitrate solutions were used to prepare SX hydrogels through bio-catalytic crosslinking in less than a minute. Silver ions were continuously reduced for up to two weeks, as confirmed by the increased absorbance of the surface plasmon at 400-450 nm in UV-vis spectra. Transmission electron microscopy (TEM) revealed that quasi-spherical silver nanoparticles were grown in a range from 5 to 30 nm. Scanning electron microscopy (SEM) revealed slit-like and hexagonal pores ranging from 30 mu m to 100 mu m in neat hydrogels. A more homogeneous pore size distribution (20-50 mu m) was observed as the concentration of the precursor increased. Rheological characterization of hydrogels showed that the storage modulus (G') increased from 200 Pa to around 3000 Pa as the concentration of silver nitrate increased, while the loss modulus (G") increased up to 20-fold (from 2 Pa to 40 Pa). The antimicrobial activity of the hydrogels was examined against highly resistant Staphylococcus aureus, Pseudomonas aeruginosa and Staphylococcus epidermidis. Hydrogels with the higher nanosilver content showed inhibition zone of 15 mm for S. aureus and 16 mm for S. epidermis, twice as large as those observed for the neat hydrogel. In conclusion, the development of antibacterial hydrogels based on spruce xylan with in situ biosynthesized silver nanoparticles represents a promising approach to addressing the challenges in the treatment of superficial skin wounds.