Development of Gelatin Hydrogel Pads as Antibacterial Wound Dressings

Gelatin hydrogel pads have been prepared from a 10 wt.-% gelatin solution that contained 2.5 wt.-% AgNO3 in 70% v/v acetic acid by a solvent-casting technique. The AgNO3-containing gelatin solution was aged under mechanical stirring for various time intervals to allow for the formation of silver nanoparticles (nAgs). The formation of nAgs was monitored by a UV-vis spectrophotometer. The morphology and size of the nAgs were characterized by transmission electron microscopy (TEM). To improve the water resistance of the hydrogels, various contents of glutaraldehyde (GTA) were added to the AgNO3-containing gelatin solution to cross-link the obtained gelatin hydrogels. These hydrogels were tested for their water retention and weight loss behavior, release characteristics of the as-loaded silver, and antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. The AgNO3-containing gelatin solution that had been aged for 5 d showed the greatest number of nAgs formed. The size of these particles, based on TEM results, was 10-11 nm. With an increase in the GTA content used to cross-link the hydrogels, the water retention, the weight loss, and the cumulative amount of silver released were found to decrease. Finally, all of the nAg-loaded gelatin hydrogels could inhibit the growth of the tested pathogens, which confirmed their applicability as antibacterial wound dressings.