E-Spun Composite Fibers of Collagen and Dragline Silk Protein: Fiber Mechanics, Biocompatibility, and Application in Stem Cell Differentiation

Abstract

Biocomposite matrices with high mechanical strength, high stability, and the ability to direct matrix-specific stem cell differentiation are essential for the reconstruction of lesioned tissues in tissue engineering and cell therapeutics. Toward this end, we used the electrospinning technique to fabricate well-aligned composite fibers from collagen and spider dragline silk protein, obtained from the milk of transgenic goats, mimicking the native extracellular matrix (ECM) on a similar scale. Collagen and the dragline silk proteins were found to mix homogeneously at all ratios in the electrospun (E-spun) fibers. As a result, the ultimate tensile strength and elasticity of the fibers increased monotonically with silk percentage, whereas the stretchability was slightly reduced. Strikingly, we found that the incorporation of silk proteins to collagen dramatically increased the matrix stability against excessive fiber swelling and shape deformation in cell culture medium. When human decidua parietalis placental stem cells (hdpPSCs) were seeded on the collagen–silk matrices, the matrices were found to support cell proliferation at a similar rate as that of the pure collagen matrix, but they provided cell adhesion with reduced strengths and induced cell polarization at varied levels. Matrices containing 15 and 30 wt % silk in collagen (CS15, CS30) were found to induce a level of neural differentiation comparable to that of pure collagen. In particular, CS15 matrix induced the highest extent of cell polarization and promoted the development of extended 1D neural filaments strictly in-line with the aligned fibers. Taking the increased mechanical strength and fiber stability into consideration, CS15 and CS30 E-spun fibers offer better alternatives to pure collagen fibers as scaffolds that can be potentially utilized in neural tissue repair and the development of future nanobiodevices.

Optimization of Glutaraldehyde Vapor Treatment for Electrospun Collagen/Silk Tissue Engineering Scaffolds

“…16 The aligned fibers mimicked the locally oriented collagen fibers in native tissues. The incorporation of synthetic spider dragline silk proteins in collagen significantly enhanced the mechanical strength and stability of the E-spun fibers.…”

“…16 The spinning conditions were optimized to obtain fibers with a desired dimension, density, and alignment. The parameters are summarized in Table S1.…”

“…16 In short, aligned freestanding fibers with various GA treatment times were collected across an 8 mm gap of an aluminum frame. Optical images (10×) were taken to estimate fiber density, and the average cross-sectional area of individual fibers was determined by AFM.…”

Identification of Wet-Spinning and Post-Spin Stretching Methods Amenable to Recombinant Spider Aciniform Silk

“…A number of methods have been utilized to spin spider silks from dope solutions including electrospinning [37][38][39][40] , microfluidics 41 , and wet-spinning 9-12, 14, 15, 42-45 . Since wetspinning has been extensively employed on recombinant spidroins, alongside recombinant honeybee silk 46 , and regenerated Bombyx mori silkworm fibroin [47][48][49][50] , we focused on applying this technique to AcSp1.…”

Adding Functions to Biomaterial Surfaces through Protein Incorporation

“…Recombinant expression of spider silks is essential due to the territorial behavior of the natural hosts [120] and has been carried out in E. coli, [121] yeast, [122] silk worms, [123] and, in a scaledup production system, transgenic goats. [124] Silk-elastin-like PROGRESS REPORT polymers (SELPs), which contain repetitive amino acid sequence motifs derived from both silk fibroin and mammalian elastin, [125] have been produced recombinantly and at up to gram per liter yields in E. coli, [126] enabling their increasingly widespread investigation in structural [127] and controlled release/drug delivery applications. [127a,128] …”