Comparison of a sealed, polymer foam biodegradable temporizing matrix against Integra® dermal regeneration template in a porcine wound model.

The aim of this study is to develop and optimize the first stage of a proposed two-stage skin graft replacement strategy. This entails creation of a material that can be applied immediately after burn excision to "temporize" the wound bed, become integrated as a "neodermis," resist contraction and infection, and provide the grounding for the second stage (an autologous, cultured composite skin). Four 8 × 8 cm wounds were generated in six pigs to assess and compare wound contraction using Integra® dermal regeneration template, a biodegradable temporizing polymer matrix (sealed and unsealed), and a secondary intention wound. All dressings were contiguous. Infection resulted in early spontaneous delamination of the Integra® marring the long-term comparison. The wounds treated with the sealed polymer thus contracted significantly less than the wounds treated with Integra® over the 28 days. Histologically, a thick layer of scar developed superficial to the Integra®, unsealed polymer, and in the secondary intention wounds when compared with the sealed polymer, where such a scar layer was characteristically minimal. No clinical signs of infection were observed for any polymer-treated wound. Once the Integra® silicone layer delaminated, wound contraction was aggressive. Optimization of the biodegradable sealing membrane is imminent, and the second stage of composite skin development is under way.

Split skin graft application over an integrating, biodegradable temporizing polymer matrix: immediate and delayed.

The objective of this study is to further investigate the NovoSorb™ biodegradable polyurethane in generating dermal scaffolds; to perform a pilot study comparing the previously used spun mat against a recently developed NovoSorb™ foam, ascertaining the optimum structure of the matrix; and to evaluate the successful matrix as an immediate adjunct to split skin grafting and as a temporizing matrix in a prospective six-pig study. A pilot study comparing a previously investigated form of the polymer (spun mat) against a new structural form, a foam, was performed. This was followed by a six-pig study of the foam matrix with three treatment arms-autologous split skin graft alone, polymer foam with immediate engraftment, and polymer foam with delayed engraftment. The foams allowed less wound contraction than the spun mats. The foam structure is less dense (cheaper to produce and having less degradation products). The material remained in situ despite clinical wound infection. Proof of concept was achieved in both treatment modalities in the main study. Split skin graft applied immediately over the polymer foam was able to engraft successfully. The result was "thicker" to pinch and "flush" with the skin surrounding the wound. There was no significant difference in the degree of wound contraction between the graft alone and the polymer plus immediate graft groups. Split skin graft also "took" when applied to the surface of a polymer that had been applied to a wound 11 days earlier, again with a thicker result, flush with the surrounding skin. Split skin grafts alone left a persisting depression. However, a significant degree of wound contraction (compared with the other two groups) was observed in the polymer plus delayed graft group. This has prompted further investigation into "sealing" the polymer foam with a membrane, to prevent evaporative water loss, when the foam is to be used as a biodegradable temporizing matrix. The studies indicate that the NovoSorb™ platform will allow the creation of two inexpensive dermal matrix products; an immediate scaffold to allow a thicker grafting result and a biodegradable temporizing matrix (BTM) for wound integration after burn debridement while donor sites become reharvestable. However, further modification on the BTM structure is necessary to further reduce wound contraction pregrafting.