Imparting commercial antimicrobial dressings with low-adherence to burn wounds

The objective of our study was to decrease the wound adherence of commercial silver based wound dressings by depositing a non-adherent layer. Our hypothesis was that this non-adherent layer will lower the dressing's adherence to burn wounds without compromising the antimicrobial activity or increasing the cytotoxicity. A polyacrylamide (PAM) hydrogel layer was grafted on two commercial silver antimicrobial dressings (silver nanocrystal dressing (NC) and silver plated dressing (SP)) using a proprietary technique. The grafted PAM served as the non-adherent layer. Dressing adherence was measured with a previously published in vitro gelatin model using an Instron mechanical force testing instrument. The dressings were challenged with two clinically retrieved bacterial strains (Methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant (MDR) Pseudomonas aeruginosa) with both a disk diffusion test, and a suspension antibacterial test. The cytotoxicity of samples to human neonatal fibroblast cells was evaluated with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. Both untreated dressings showed high peeling energy: 2070 +/- 453 J/m(2) (NC) and 669 +/- 68 J/m(2) (SP), that decreased to 158 +/- 119 J/m(2) (NC) and 155 +/- 138 J/m(2) (SP) with the PAM deposition. Addition of the PAM caused no significant difference in zone of inhibition (ZOI) (disk diffusion test) or antibacterial kinetics (suspension test) against both bacteria (p > 0.05, n = 6) in either dressing. Survival of fibroblasts was improved by the PAM grafting from 48 +/- 5% to 60 +/- 3% viable cells in the case of NC and from 55 +/- 8% to 61 +/- 4% viable cells in SP (p < 0.05, n = 12). It was concluded that PAM as a non-adherent layer significantly decreases the adherence of these two commercial antimicrobial dressings in an in vitro gelatin model while preserving their antimicrobial efficacy, and reducing their cytotoxicity. (C) 2016 Elsevier Ltd and ISBI. All rights reserved.