Stimulated migration and penetration of vascular endothelial cells into poly (L-lactic acid) scaffolds under flow conditions.

BACKGROUND: The initial procedure of the development of engineered tissues is cell seeding into three-dimensional polymer scaffolds. However, it is hard to make the cells invade into scaffold due to the characteristic of pore and material. Electrospun poly (L-lactic acid) scaffold and flow perfusion system were used to overcome these seeding problems. RESULTS: Before starting the experiment, we set up the parallel plate chamber system to observe endothelial cell migration under flow condition. In individual cell migration model, human umbilical endothelial cells started to migrate in the direction of flow at 8 dyne/cm(2) and we observed the cytoskeleton alignment at 8 dyne/cm(2). This study has demonstrated the possibility to evaluate and analyze cell migration using the parallel plate chamber system and we may predict in vivo cell migration under flow condition based on these results. Also the flow perfusion system was established for the effective cell seeding into at three dimensional scaffolds. Moreover, shear stress induced by flow can enhance cell migration into PLLA scaffold that is in the form of cotton. CONCLUSIONS: Result indicated that cell penetration was achieved under flow condition better and more than under static condition throughout the matrix.

Polydopamine-mediated immobilization of multiple bioactive molecules for the development of functional vascular graft materials.

In this study, we introduced a simple method for polydopamine-mediated immobilization of dual bioactive factors for the preparation of functionalized vascular graft materials. Polydopamine was deposited on elastic and biodegradable poly(lactic acid-co-ɛ-caprolactone) (PLCL) films, and a cell adhesive RGD-containing peptide and basic fibroblast growth factor were subsequently immobilized by simple dipping. We used an enzyme-linked immunosorbent assay and fluorescamine assay to confirm that we had stably immobilized bioactive molecules on the polydopamine-coated PLCL film in a reaction time-dependent manner. When human umbilical vein endothelial cells (HUVEC) were cultured on the prepared substrates, the number of adherent cells and proliferation of HUVEC for up to 14 days were greatest on the film immobilized with dual factors. On the other hand, the film immobilized with RGD peptide exhibited the highest migration speed compared to the other groups. The expression of cluster of differentiation 31 and von Willebrand factor, which indicates maturation of endothelial cells, was highly stimulated in the dual factor-immobilized group, and passively adsorbed factors showed a negligible effect. The immobilization of bioactive molecules inspired by polydopamine was successful, and adhesion, migration, proliferation and differentiation of HUVEC were synergistically accelerated by the presence of multiple signaling factors. Collectively, our results have demonstrated that a simple coating with polydopamine enables the immobilization of multiple bioactive molecules for preparation of polymeric functionalized vascular graft materials.

Mussel-inspired immobilization of vascular endothelial growth factor (VEGF) for enhanced endothelialization of vascular grafts.

Most polymeric vascular prosthetic materials have low patency rate for replacement of small diameter vessels (<5 mm), mainly due to failure to generate healthy endothelium. In this study, we present polydopamine-mediated immobilization of growth factors on the surface of polymeric materials as a versatile tool to modify surface characteristics of vascular grafts potentially for accelerated endothelialization. Polydopamine was deposited on the surface of biocompatible poly(L-lactide-co-ε-caprolactone) (PLCL) elastomer, on which vascular endothelial growth factor (VEGF) was subsequently immobilized by simple dipping. Surface characteristics and composition were investigated by using scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Immobilization of VEGF on the polydopamine-deposited PLCL films was effective (19.8 ± 0.4 and 197.4 ± 19.7 ng/cm(2) for DPv20 and DPv200 films, respectively), and biotin-mediated labeling of immobilized VEGF revealed that the fluorescence intensity increased as a function of the concentration of VEGF solution. The effect of VEGF on adhesion of HUVECs was marginal, which may have been masked by polydopamine layer that also enhanced cell adhesion. However, VEGF-immobilized substrate significantly enhanced proliferation of HUVECs for over 7 days of in vitro culture and also improved their migration. In addition, immobilized VEGF supported robust cell to cell interactions with strong expression of CD 31 marker. The same process was effective for immobilization of basic fibroblast growth factor, demonstrating the robustness of polydopamine layer for secondary ligation of growth factors as a simple and novel surface modification strategy for vascular graft materials.