Ji-hye Lee

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.

Heparin-coated superparamagnetic iron oxide for in vivo MR imaging of human MSCs.

Human mesenchymal stem cells (hMSCs) offer significant therapeutic potential in the field of regenerative medicine and high-resolution magnetic resonance imaging (MRI) is useful modality to visualize in vivo kinetics of transplanted stem cells. For successful MR imaging, there is a great need for effective contrast agents for stem cell labeling with high uptake yield and low toxicity. Here, we present superparamagnetic iron oxide (SPIO) nanoparticles coated with unfractionated heparin (UFH-SPIO) as a new negative contrast agent for in vivo MR imaging of hMSCs. The uptake of UFH-SPIO by hMSCs was effective without the aid of transfection agents, which was dependent on the concentration and exposure time. The uptake efficiency of UFH-SPIO was greater than that of DEX-SPIO (SPIO coated with dextran) by approximately 3 folds when treated for 1 h. TEM and Prussian blue staining confirmed that UFH-SPIO nanoparticles were internalized into the cytosol of hMSCs which existed during in vitro subculture for 28 days. Low temperature endocytosis inhibition assay demonstrated that the incorporation of UFH-SPIO into hMSCs was likely to be mediated by endocytosis. When the phantom of UFH-SPIO-labeled hMSCs was visualized with 3-T T(2)-weighted MRI, the hypointensity signals of UFH-SPIO-labeled hMSCs were linearly correlated with the concentration of the nanoparticles. The cellular labeling using UFH-SPIO did not reduce the viability, proliferation or differentiation potential to osteogenic and adipogenic lineages of hMSCs. When the UFH-SPIO-labeled hMSCs were transplanted into the left renal subcapsular membranes of nude mice, they were successfully visualized and detected by T(2) and T(2)(∗)-weighted MRI for a month. Collectively, these results suggest that UFH-SPIO nanoparticles are promising as a new MRI contrast agent for in vivo long-term tracking of hMSCs.

Rapid Transfer of Endothelial Cell Sheet Using a Thermosensitive Hydrogel and Its Effect on Therapeutic Angiogenesis

In this study, thermosensitive hydrogels incorporated with multiple cell-interactive factors were developed as a substrate to form monolayer of human umbilical vein endothelial cells (HUVECs) that can be detached and transferrable to target sites as a cell-sheet in response to temperature change. The cell adhesive peptide (RGD) and growth factor (bFGF) covalently incorporated within the hydrogel significantly enhanced adhesion and proliferation of HUVECs, allowing for the formation of their confluent monolayer. Meanwhile, the precisely controllable change in the size of the hydrogels was observed by a repeated increase and decrease in temperature from 37 to 4 °C. By exploiting this unique behavior, the detachment and transfer of HUVEC sheet confluently cultured at 37 °C was rapidly induced within 10 min by expansion of the hydrogels when the temperature was decreased to 4 °C. The transferred cell sheet was highly viable and maintained robust cell-cell junction. Finally, the process of cell sheet transfer was directly applied onto an ischemic injury in the hind limb of mice. The transplanted HUVECs as a sheet retarded tissue necrosis over 14 days in comparison with that of direct injection of the same number of cells. Our results suggest that the developed multifunctional Tetronic-tyramine hydrogels could serve as an ideal substrate to modulate the formation of an endothelial cell layer that could potentially be utilized to treat peripheral arterial disease.

Release Kinetics and in vitro Bioactivity of Basic Fibroblast Growth Factor: Effect of the Thickness of Fibrous Matrices

In this study, we fabricated non-woven matrices using blends of polycaprolactone and gelatin with various spinning volumes to control the immobilized heparin content, which was ultimately intended to increase the immobilization efficiency of bFGF. The amount of bFGF on the heparin conjugated fibrous matrices depended on the thicknesses of the swollen matrices ranging from 35.4 ± 6.5 to 162.3 ± 14.0 ng and ≈90% of the bFGF was gradually released over a period of up to 56 d. The released bFGF enhanced the proliferation of human umbilical vein endothelial cells and human mesenchymal stem cells. In conclusion, our heparin-conjugated fibrous matrices have the potential to be used as a growth factor delivery system in tissue engineering applications.