Effect of Enzymatic Degradation On the Mechanical Properties of Biologic Scaffold Materials

Afua H Annor, BS, Michael E Tang, BS, Chi Lun Pui, BS, Gregory C Ebersole, MS MS, Margaret M Frisella, RN, Brent D Matthews, MD, Corey R Deeken, PhD. Washington University in St. Louis

 

 INTRODUCTION: In the body, biologic scaffolds are exposed to matrix metalloproteinases (MMPs) which are produced by inflammatory cells (neutrophils). Scaffolds must resist enzymatic degradation and support cellular attachment, neotissue deposition, and angiogenesis. The purpose of this study was to evaluate the effects of enzymatic degradation on the mechanical properties of biologic scaffold materials.

METHODS: Nine materials were evaluated (4 porcine dermis – PermacolTM, CollaMendTM, StratticeTM, XenMatrixTM; 2 human dermis – AlloMaxTM, FlexHD®; 2 bovine pericardium – Veritas®, PeriGuard®; and 1 porcine small intestine submucosa – SurgisisTM). Sixty (n=60) specimens were prepared of each. Ten specimens (n=10) were hydrated in saline at 37°C and subjected to uniaxial tension at a rate of 300mm/min until failure to establish the baseline “0 hour” properties before exposure to collagenase. The other fifty specimens (n=50) were incubated in a collagenase solution at 37°C for 2, 6, 12, 24, or 30 hours (n=10 each group). Specimens were then subjected to uniaxial tensile testing at a rate of 300mm/min until failure. A one-way analysis of variance (ANOVA) was performed, followed by a Fisher’s LSD post-test as appropriate. Statistical significance was set at the p<0.05 level.

RESULTS: Tensile strength was significantly reduced after 30 hours of exposure to collagenase for CollaMendTM, AlloMaxTM, Veritas®, StratticeTM, XenMatrixTM, PermacolTM, and FlexHD® (p<0.01), while PeriGuard® demonstrated a slight increase in tensile strength (p=0.0188). Differences were also observed between crosslinked and non-crosslinked scaffolds of the same tissue type. For instance, crosslinked bovine pericardium (PeriGuard®) maintained greater tensile strength than non-crosslinked bovine pericardium (Veritas®) throughout all exposure periods (p<0.0001). Similarly, crosslinked porcine dermis (PermacolTM) maintained greater tensile strength than non-crosslinked porcine dermis (StratticeTM and XenMatrixTM) throughout all exposure periods (p<0.0001).

Some scaffolds did not survive the longer incubation periods and were so degraded that mechanical testing was not possible. Specimens were measurable for PermacolTM, CollaMendTM, StratticeTM, FlexHD®, and PeriGuard® scaffolds throughout all exposure periods up to 30 hours. However, specimens of SurgisisTM and Veritas® were only measurable up to the 6 hour exposure period, and specimens of XenMatrixTM and AlloMaxTM were only measurable up to the 12 hour exposure period.

CONCLUSIONS: Materials that deteriorate rapidly after in vitro enzymatic exposure may be at risk for rapid in vivo degradation and loss of strength when exposed to a wound environment with elevated levels of MMPs.


Session Number: SS01 – Basic Science
Program Number: S001

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