Evaluation of wound-covering materials

Physical and in vivo (burned rat model) evaluations as wound coverings were performed for 1) a freeze-dried collagen/poly (ϵ-caprolactone) (PCL) film laminate, 2) a freeze-dried PCL “foam”/PCL film laminate, and 3) a heat-dried collagen/PCL film laminate. Porcine skin and cadaver skin were also evalulated in vivo for the purpose of comparison. Water-vapor transmission rates and Young's moduli were measured. The degrees of adherence of the coverings to the wound were measured. Grafts which became significantly adherent (>150 dyne/cm2) to the wound within 1 day were most successful in promoting the formation of a viable tissue bed which appeared ready to accept further grafting. The force required to remove the PCL foam laminate from a full-thickness excision wound was found to increase from 170 dyne/cm2 on the first day postgraft to 1500 dyne/cm2 by the tenth day. The force required to remove freeze-dried collagen laminate remained constant at 200 dyne/cm2 over the 10 day test period. For the heat-dried collagen laminate, a force of only 50 dyne/cm2 was required on day 1, increasing to 200 dyne/cm2 on day 6. Insensible water-loss rates of animals grafted with the laminates were found to be similar to those from animals with human cadaver skin grafts and less than that from animals with porcine skin grafts. When moistened, the laminates prepared using the freeze-dried materials were flexible and somewhat transparent permitting observation of the wound.