Tendon-derived matrix crosslinking techniques for electrospun multi-layered scaffolds.

Tendon tears are common and healing often occurs incompletely and by fibrosis. Tissue engineering seeks to improve repair, and one approach under investigation uses cell-seeded scaffolds containing biomimetic factors. Retention of biomimetic factors on the scaffolds is likely critical to maximize their benefit, while minimizing the risk of adverse effects, and without losing the beneficial effects of the biomimetic factors. The aim of the current study was to evaluate cross-linking methods to enhance the retention of tendon-derived matrix (TDM) on electrospun poly(ε-caprolactone) (PCL) scaffolds. We tested the effects of ultraviolet (UV) or carbodiimide (EDC:NHS:COOH) crosslinking methods to better retain TDM to the scaffolds and stimulate tendon-like matrix synthesis. Initially, we tested various crosslinking configurations of carbodiimide (2.5:1:1, 5:2:1, and 10:4:1 EDC:NHS:COOH ratios) and UV (30 s 1 J/cm2 , 60 s 1 J/cm2 , and 60 s 4 J/cm2 ) on PCL films compared to un-crosslinked TDM. We found that no crosslinking tested retained more TDM than coating alone (Kruskal-Wallis: p > .05), but that human adipose stem cells (hASCs) spread most on the 60 s 1 J/cm2 UV- and 2.5:1:1 EDC-crosslinked films (Kruskal-Wallis: p < .05). Next, we compared the effects of 60 s 1 J/cm2 UV- and 2.5:1:1 EDC-crosslinked to TDM-coated and untreated PCL scaffolds on hASC-induced tendon-like differentiation. UV-crosslinked scaffolds had greater modulus and stiffness than PCL or TDM scaffolds, and hASCs spread more on UV-crosslinked scaffolds (ANOVA: p < .05). Fourier transform infrared spectra revealed that UV- or EDC-crosslinking TDM did not affect the peaks at wavenumbers characteristic of tendon. Crosslinking TDM to electrospun scaffolds improves tendon-like matrix synthesis, providing a viable strategy for improving retention of TDM on electrospun PCL scaffolds.

Bi-functional nanoparticle-stabilized hydrogel colloidosomes as both extracellular matrix and bioactive factor delivery vehicle.

Maintaining both cell-cell and cell-extracellular matrix (ECM) interactions is often a critical component of three-dimensional (3D) tissue regeneration. In high-density cell condensation systems, lack of appropriate cell-ECM interactions can result in limited and/or slow cell differentiation and tissue formation. To address these problems, a colloidosome microsphere system that is composed of a gelatin hydrogel core and a porous nanoparticle shell is developed. The colloidosome microsphere functions as an ECM and morphogen carrier for the induction of cartilage formation of high-density human mesenchymal stem cell (hMSC) in 3D cultures. With the protection of the nanoparticle shell, the colloidosome microspheres can be readily suspended in aqueous solution without clumping, thus incorporated homogeneously within high-density cell condensations. The gelatin-based colloidosome microspheres stimulate chondrogenesis of hMSCs and degrade rapidly to facilitate ECM remodeling for new tissue formation. When loaded with human transforming growth factor-ß1, a potent chondrogenic morphogen, the colloidosomes serve as a bioactive factor delivery vehicle as well. The dual functionality of the colloidosomes as an ECM and a growth factor carrier effectively supports the chondrogenic differentiation of high-density hMSC condensations. These capabilities render the colloidosomes a promising platform system amenable to large-scale production of high-density 3D tissue culture constructs.