Robust Durability and Resistance to Degradation of a Native Type I Collagen Matrix with PHMB in vitro

Wound fluid is an essential component of the normal wound healing process that first appears in the wound during the inflammatory phase. There are significant differences in the wound fluid composition of wounds progressing towards normal healing compared to chronic wounds.1 Chronic wound fluid contains a cocktail of elements, including higher levels of matrix metalloproteinases (MMPs), specifically MMP-1 and MMP-8, which are responsible for increased extracellular matrix (ECM) destruction.2,3

In the current study, we have developed an in vitro model of chronic wound conditions using simulated wound fluid (SWF) and Collagenase I (MMP-1) and II (MMP-8). Using this model, we have evaluated degradation characteristics of a 2-layer (PCMPº) and 5-layer PCMP (PCMP-XT†) consisting of purified native type I collagen ECM with polyhexamethylene biguanide (PHMB) and compared that to an oxidized regenerated cellulose/collagen matrix (ORC/C*). PCMP, PCMP-XT, and ORC/C were exposed to collagenase (1mg/mL) type I, collagenase type II (1mg/ml), or SWF plus collagenases type I and II and ECM degradation was evaluated for up to 7 days at 37°C.

Degradation was evaluated by measuring collagen released into the degradation solution and by taking dry weights of samples. When evaluating matrix degradation, we found that PCMP and PCMP-XT were resistant to robust degradation by collagenases type I and II alone compared to ORC/C, which was readily degraded. Treatment with SWF plus collagenase I and II increased PCMP and PCMP-XT degradation when compared to collagenase only groups, but both were much more resistant to degradation than ORC/C.

We found the additional layers (5 vs. 2) within PCMP-XT resulted in a slower rate of degradation, suggesting the additional collagen layers may result in enhanced durability. We found that ORC/C was completely degraded by day 7 in all treatment groups. These results highlight the durability of PCMP and PCMP-XT in an in vitro model of a chronic wound environment. Additionally, the increased layers in PCMP-XT resulted in additional benefits of longer duration and slower degradation in this model.