Marrow Stromal Cell Reponse to Fiber-Reinforced Laminated Nanocomposites
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1235-RR05-05
Marrow Stromal Cell Response to Fiber-Reinforced Laminated Nanocomposites Junyu Ma, Weijie Xu, and and Esmaiel Jabbari* Biomimetic Materials and Tissue Engineering Laboratories Department of Chemical Engineering University of South Carolina, Columbia, SC 29208, U.S.A. ABSTRACT Current biomaterials as a scaffold for bone regeneration are limited by the extent of degradation concurrent with bone formation, mechanical strength, and the extent of osteogenic differentiation of marrow stromal cells migrating from the surrounding tissues. In this project, a novel laminated nanocomposite scaffold is fabricated, consisting of poly (L-lactide ethylene oxide fumarate) (PLEOF) hydrogel reinforced with poly (L-lactide acid) (PLLA) electrospun nanofibers and hydroxyapatite (HA) nanoparticles. The laminated nanocomposites were fabricated by dry-hand lay up technique followed by compression molding and thermal crosslinking. The laminated nanocomposites were evaluated with respect to mechanical strength and osteogenic differentiation of marrow stromal (BMS) cells. Laminates showed modulus values much higher than that of hydrogel or fiber. The effect of laminated nanocomposites on osteogenic differentiation of BMS cells was determined in terms of ALPase activity and calcium content. Our results demonstrate that grafting RGD peptide to a PLEOF/HA hydrogel reinforced with PLLA nanofibers synergistically enhances osteogenic differentiation of BMS cells. INTRODUCTION Bone is a composite matrix consisting of a mineral and a collagenous phase [1]. Bone exhibits hierarchical levels of organization from macroscopic to microscopic to nanoscale [2]. On the microscale, layers of fibrils are glued together by ECM proteins to form laminated structures that make bone elastic and allow diffusion of nutrients and oxygen to cells embedded in the bone matrix [3]. The apatite crystals provide mechanical support in compression, the laminated structure of the osteons confers elasticity, while the hydrophilic ECM proteins allow diffusion of nutrients and oxygen to cells in the bone matrix. The objective of this work was to develop a composite matrix to mimic the laminated structure of osteons in bone. Sheets of PLLA nanofibers were fabricated by electrospinning. The sheets were dipped in a hydrogel/HA precursor solution, stacked and pressed together, and allowed to crosslink by photopolymerization to form a fiber-reinforced laminated structure. The precursor solution is based on poly(lactide-co-ethylene oxide fumarate) (PLEOF) macromer that can be crosslinked in aqueous environment with redox or ultraviolet initiators to produce a biodegradable hydrogel [4, 5]. The crosslink density can be adjusted by the initiator concentration and density of fumarate groups on PLEOF chains [6]. In this work, the effect of lamination on Young’s modulus of the nanofiber-reinforced laminated composite is investigated. In addition, BMS cells seeded on RGD-conjugated laminated composites are evaluated with respect to osteogenic differentiation by measuring alka
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