Wound-dressing materials with antibacterial activity from electrospun gelatin fiber mats containing silver nanoparticles

Ultrafine gelatin fiber mats with antibacterial activity against some common bacteria found on burn wounds were prepared from a gelatin solution (22%w/v in 70 vol% acetic acid) containing 2.5 wt% AgNO3. Silver nanoparticles (nAg), a potent antibacterial agent, first appeared in the AgNO3-containing gelatin solution after it had been aged for at least 12 h, with the amount of nAg increasing with increasing aging time. The average diameters of the as-formed nAg ranged between 11 and 20 nm. Electrospinning of both the base and the 12 h-aged AgNO3-containing gelatin solutions resulted in the formation of smooth fibers, with average diameters of ∼230 and ∼280 nm, respectively. The average diameter of the as-formed nAg in the electrospun fibers from the 12 h-aged AgNO3-containing gelatin solution was ∼13 nm. The nAg-containing gelatin fiber mats were further cross-linked with moist glutaraldehyde vapor to improve their stability in an aqueous medium. Both the weight loss and the water retention of the nAg-containing gelatin fiber mats in acetate buffer (pH 5.5), distilled water (pH 6.9) or simulated body fluid (SBF; pH 7.4) decreased with increasing cross-linking time. The release of Ag+ ions from both the 1- and 3 h-cross-linked nAg-containing gelatin fiber mats - by the total immersion method in acetate buffer and distilled water (both at a skin temperature of 32 °C) - occurred rapidly during the first 60 min, and increased gradually afterwards; while that in SBF (at the physiological temperature of 37 °C) occurred more gradually over the testing period. Lastly, the antibacterial activity of these materials, regardless of the sample types, was greatest against Pseudomonas aeroginosa, followed by Staphylococcus aureus, Escherichia coli, and methicillin-resistant S. aureus, respectively.