Gelatin-based films containing clinoptilolite-Ag for application as wound dressing

Dressings used in burns and chronic wounds treatment must present antimicrobial characteristics. Silver-based compounds are used for a long time as antiseptics, but they present problems related to the release of silver. In order to control the release, Ag⁺ ions may be immobilized in supports that must be dispersed in the film used as wound dressing. In this work gelatin-based films using glycerol as plasticizer and incorporated with different concentrations of clinoptilolite zeolite impregnated with silver ions were prepared and characterized, and the potential antimicrobial activity was investigated. For this purpose, films were produced by casting and evaluated in relation to their mechanical, chemical, thermal, morphological and antimicrobial properties, in addition the amount of silver present in the films was quantified and the kinetics of Ag⁺ release in vitro was studied. The antimicrobial analysis was done qualitatively, using Escherichia coli and Staphylococcus aureus bacteria and the microorganisms commonly present on human skin collected with a swab, and quantitatively, using Escherichia coli and Staphylococcus aureus. Characterization tests demonstrated that the glycerol concentration of 25% and the zeolite concentration of 0.5% resulted in films with more suitable properties for wound dressing applications and the silver release test showed that the release of the active compound occurs slowly, as expected. All gelatin/clinoptilolite-Ag films showed antibacterial activity against Staphylococcus aureus and human skin bacteria, not presenting expressive differences on the size of the formed halo. Moreover, by the quantitative antimicrobial analisys, it was observed that as the glycerol concentration increases, the antimicrobial action was faster and at the end of the experiment, there were no S. aureus in the solutions where the films were immersed and for the assay with E. coli, the bactericidal activity is slower and probably is needed a higher concentration of silver ions in the sample to completely inhibit the bacteria. However, the bactericidal activity of the gelatin/clinoptilolite-Ag films was satisfactory due its effectiveness in reducing bacterial growth of E. coli and S. aureus. Based on these results the prepared gelatin/clinoptilolite-Ag films could serve as a promising wound dressing with great antibacterial properties, thus possibly helping also the wound healing.