title: Static axial stretching enhances the mechanical properties and cellular responses of fibrin microthreads.
abstract: Fibrin microthreads are a platform technology that can be used for a variety of applications, and therefore the mechanical requirements of these microthreads differ for each tissue or device application. To develop biopolymer microthreads with tunable mechanical properties, we analyzed fibrin microthread processing conditions to strengthen the scaffold materials without the use of exogenous crosslinking agents. Fibrin microthreads were extruded, dried, rehydrated and static axially stretched 0-200% of their original lengths; then the mechanical and structural properties of the microthreads were assessed. Stretching significantly increased the tensile strength of microthreads 3-fold, yielding scaffolds with tensile strengths and stiffnesses that equaled or exceeded values reported previously for carbodiimide crosslinked threads without affecting intrinsic material properties such as strain hardening or Poisson's ratio. Interestingly, these stretching conditions did not affect the rate of proteolytic degradation of the threads. The swelling ratios of stretched microthreads decreased, and scanning electron micrographs showed increases in grooved topography with increased stretch, suggesting that stretching may increase the fibrillar alignment of fibrin fibrils. The average cell alignment with respect to the longitudinal axis of the microthreads increased 2-fold with increased stretch, further supporting the hypothesis that stretching microthreads increases the alignment of fibrin fibrils on the surfaces of the scaffolds. Together, these data suggest that stretching fibrin microthreads generates stronger materials without affecting their proteolytic stability, making stretched microthreads ideal for implantable scaffolds that require short degradation times and large initial loading properties. Further modifications to stretched microthreads, such as carbodiimide crosslinking, could generate microthreads to direct cell orientation and align tissue deposition, with additional resistance to degradation for use as a long-term scaffold for tissue regeneration.
authors: Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA; Bioengineering Institute, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
authors: Jonathan M
authors: JM
authors: Grasman
authors: Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
authors: Laura M
authors: LM
authors: Pumphrey
authors: Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
authors: Melissa
authors: M
authors: Dunphy
authors: Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
authors: James
authors: J
authors: Perez-Rogers
authors: Biomedical Engineering Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA; Bioengineering Institute, Worcester Polytechnic Institute, Worcester, MA 01609, USA. Electronic address: gpins@wpi.edu.
authors: George D
authors: GD
authors: Pins
mesh_terms: D000818:Animals; D002460:Cell Line; D005337:Fibrin / Q000737:chemistry*; D008422:Materials Testing; D051379:Mice; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism*; D059748:Proteolysis; D013718:Tensile Strength; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D005337:Fibrin
keywords: Cell alignment; Fibrin; Microthreads; Scaffolds; Tissue engineering