Previously, we have shown in a cross-comparison study that multifunctional photopolymerized semi-interpenetrating network (sIPN) system is an effective donor site treatment in a swine model. The advantages of sIPN include spray-on application, in-situ photopolymerization, and ability to cover large contoured areas. sIPN has also been shown to be an effective delivery vehicle for keratinocyte growth factor, dexamethasone, bupivacaine, and silver sulfadiazine in vitro. Our aim for this study was to show that these products delivered to the wound bed with sIPN would not change the wound healing characteristics compared to the control site through qualitative clinical evaluation and to compare the rate and quality of donor site healing through histologic evaluation.
Eight Yucatan swine of 40lbs each were randomly divided into four groups of two pigs prior to surgery. Each animal had 5.6 % total body surface area of skin harvested from two different dorsal regions, with one at 22/1000th inch and the other at 30/1000th inch setting on the dermatome. Each test site on each animal was then sequentially dressed with 50 cm2 of Xeroform gauze, sIPN, sIPN loaded with 0.5% bupivacaine, or sIPN loaded with 1% silver sulfadiazine. sIPN with or without soluble drugs were applied as liquid then photopolymerized in situ to form an elastic covering. Each of the test areas was separated by 50 cm2 of autograft which was used to divide the test areas. Wound assessment and euthanasia occurred at days 7, 9, 14, and 21 days. A full thickness biopsy was taken from each of the study areas for histological analysis.
By 14 days, all areas show complete epidermal coverage histologically. The 30/1000th inch site revealed a thicker, more irregular dermis compared to the 22/1000th site. Evaluation of the day 21 sites revealed equal thinning and flattening of the new epidermis. No site showed full restoration of the rete ridges. No signs of infection were seen in clinical or histological evaluations of any treatment.
The addition of bupivacaine and silver sulfadiazine to sIPN does not show any alterations in wound healing of a donor site in a swine model when compared with sIPN without loaded drugs and a standard control dressing. This efficacy may be coupled with established localized sIPN drug delivery profiles and allow further studies to evaluate the efficacy of these drugs to promote healing, eradicate and prevent infection, and manage pain.