title: Effect of enzymatic degradation on the mechanical properties of biological scaffold materials.
abstract: BACKGROUND
  Biological scaffolds must support a complex balance of resisting enzymatic degradation while promoting tissue remodeling. Thus, the purpose of this study was to evaluate the effects of in vitro enzymatic exposure on the mechanical properties of biological scaffolds. It was hypothesized that exposure to an enzyme solution would result in decreased tensile strength and that crosslinked scaffolds would resist enzymatic degradation more effectively than noncrosslinked scaffolds.
  
  
  METHODS
  Nine scaffolds were evaluated (four porcine dermis: Permacol™, CollaMend™, Strattice™, XenMatrix™; two human dermis: AlloMax™, FlexHD(®); two bovine pericardium: Veritas(®), PeriGuard(®); and one porcine small intestine submucosa: Surgisis™). Ten specimens (n = 10) were hydrated in saline at 37 °C and subjected to uniaxial testing to establish baseline properties. 50 specimens (n = 50) were incubated in collagenase solution at 37 °C for 2, 6, 12, 24, or 30 h (n = 10 each group) followed by uniaxial tensile testing.
  
  
  RESULTS
  Tensile strength was significantly reduced after 30 h for CollaMend™, AlloMax™, Veritas(®), Strattice™, XenMatrix™, Permacol™, and FlexHD(®) (p < 0.01), while PeriGuard(®) demonstrated a slight increase in tensile strength (p = 0.0188). Crosslinked bovine pericardium (PeriGuard(®)) maintained greater tensile strength than noncrosslinked bovine pericardium (Veritas(®)) throughout all exposure periods (p < 0.0001). Similarly, crosslinked porcine dermis (Permacol™) maintained greater tensile strength than noncrosslinked porcine dermis (Strattice™ and XenMatrix™) throughout all exposure periods (p < 0.0001).
  
  
  CONCLUSIONS
  Materials that deteriorate rapidly after in vitro enzymatic exposure may also deteriorate rapidly in vivo, particularly when exposed to a wound environment with elevated levels of matrix metalloproteinases. Permacol™, CollaMend™, Strattice™, FlexHD(®), and PeriGuard(®) survived the longest incubation period (30 h) and withstood mechanical testing. XenMatrix™, AlloMax™, Veritas(®), and Surgisis™ degraded more quickly and did not survive the longer exposure periods. Scaffolds that maintain strength characteristics after in vitro collagenase exposure may be advantageous for long-term hernia repair scenarios where elevated enzyme levels are expected.
authors.affiliation: Section of Minimally Invasive Surgery, Department of Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8109, St. Louis, MO 63110, USA.
authors.forename: Afua H
authors.initials: AH
authors.lastname: Annor
authors.forename: Michael E
authors.initials: ME
authors.lastname: Tang
authors.forename: Chi Lun
authors.initials: CL
authors.lastname: Pui
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Ebersole
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Frisella
authors.forename: Brent D
authors.initials: BD
authors.lastname: Matthews
authors.forename: Corey R
authors.initials: CR
authors.lastname: Deeken
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D002417:Cattle; D017364:Collagenases / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D020782:Matrix Metalloproteinases / Q000737:chemistry*; D011126:Polypropylenes / Q000737:chemistry; D011138:Polytetrafluoroethylene / Q000737:chemistry; D013314:Stress, Mechanical; D013526:Surgical Mesh; D013552:Swine; D013718:Tensile Strength; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D011126:Polypropylenes; D011138:Polytetrafluoroethylene; D017364:Collagenases; D020782:Matrix Metalloproteinases