Regulation of material properties in electrospun scaffolds: Role of cross-linking and fiber tertiary structure.
We cross-linked scaffolds of electrospun collagen to varying degrees with glutaraldehyde using an ethanol-based solvent system and subsequently defined how the percentage of cross-linking impacts bulk and microscale material properties and fiber structure. At hydration, electrospun fibers underwent coiling; the extent of coiling was proportional to the percentage of cross-linking introduced into the samples and was largely suppressed as cross-linking approached saturation. These data suggest that electrospun collagen fibers are not deposited in a minimal energy state; fiber coiling may reflect a molecular reorganization. This result has functional/structural implications for protein-based electrospun scaffolds. Changes in fiber topology that develop during post-electrospinning processing may alter monomer organization, mask or unmask receptor binding sites, and/or change the biological properties of these nanomaterials. Hydrated scaffolds were mounted into a custom stretching device installed on a microscope stage and photographed after incremental changes in strain. Changes in fiber alignment were measured using the two-dimensional fast Fourier transform method. Fibers in all scaffolds underwent alignment in response to strain; however, the rate and extent of alignment that could be achieved varied as a function of cross-linking. We propose four distinct modes of scaffold response to strain: fiber uncoiling, fiber reorientation, fiber elongation and interfiber sliding. We conclude that bulk material properties and local microscale architecture must be simultaneously considered to optimize the performance of electrospun scaffolds.
Newton
Dan
D
Virginia Commonwealth University, Department of Anatomy and Neurobiology, 1101 East Marshall Street, Box 980709, Richmond, VA 23298, USA.
Mahajan
Raul
R
Ayres
Chantal
C
Bowman
James R
JR
Bowlin
Gary L
GL
Simpson
David G
DG
D000818:Animals; D016880:Anisotropy; D001672:Biocompatible Materials / Q000737:chemistry*; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods; D005583:Fourier Analysis; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology; D013499:Surface Properties; D013696:Temperature; D023822:Tissue Engineering / Q000379:methods*
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D003094:Collagen