Sung In Jeong

Manufacture of elastic biodegradable PLCL scaffolds for mechano-active vascular tissue engineering

A soft and very elastic poly(lactide-co-ε-caprolactone) (PLCL)(50:50, M n 185 × 103) was synthesized. Tubular scaffolds were prepared by an extrusion-particulate leaching method for mechano-active vascular tissue engineering. The copolymer was very flexible but completely rubber-like elastic. Even the high porous PLCL scaffolds (90% salt wt) exhibited 200% elongation, but recovery over 85% in a tensile test. Moreover, the PLCL scaffolds maintained their high elasticity also in culture media under cyclic mechanical strain conditions. The highly porous scaffold (90% salt wt) withstood for an initial 1 week without any deformation and sustained for 2 weeks in culture media under cyclic stress of 10% amplitude and at 1 Hz frequency which are similar to the natural vascular conditions. Vascular smooth muscle cells (VSMCs) were seeded on to the PLCL scaffolds. The cell adhesion and proliferation on the scaffolds of various pore-size were increased with increasing pore size. For the pore sizes of 50-100 μm, 100-150 μm, 150-200 μm and 200-250 μm, the ratios of cell numbers were about 1:1.2:1.9:2.2, respectively, at both 12 h and 5 days. Similarly, the higher porous scaffolds exhibited more cell adhesion and proliferation compared to lower porous one, where the effect was more pronounced in the longer proliferation period. SMC-seeded scaffolds were implanted subcutaneously in athymic nude mice to confirm the biocompatibility. Such a high elastic property and proper biocompatibility to SMCs of PLCL scaffolds prepared in this study will be very useful to engineer SM-containing tissues such as blood vessels under mechanically dynamic environments (mechano-active tissue engineering).

Transplantation of mesenchymal stem cells within a poly(lactide‐co‐ɛ‐caprolactone) scaffold improves cardiac function in a rat myocardial infarction model

Cardiac tissue engineering has been proposed as an appropriate method to repair myocardial infarction (MI). Evidence suggests that a cell with scaffold combination was more effective than a cell‐only implant. Nevertheless, to date, there has been no research into elastic biodegradable poly(lactide‐co‐ε‐caprolactone) (PLCL) scaffolds. The aim of this study was to investigate the effect of mesenchymal stem cells (MSCs) with elastic biodegradable PLCL scaffold transplants in a rat MI model.

Development of Electroactive and Elastic Nanofibers that contain Polyaniline and Poly(L-lactide-co-ε-caprolactone) for the Control of Cell Adhesion

In this work, electrically conductive polyaniline (PAni) doped with camphorsulfonic acid (CPSA) is blended with poly(L-lactide-co-epsilon-caprolactone) (PLCL), and then electrospun to prepare uniform nanofibers. The CPSA-PAni/PLCL nanofibers show a smooth fiber structure without coarse lumps or beads and consistent fiber diameters (which range from 100 to 700 nm) even with an increase in the amount of CPSA-PAni (from 0 to 30 wt.-%). However, the elongation at break decreases from 391.54 +/- 9.20% to 207.85 +/- 6.74% when 30% of CPSA-PAni is incorporated. Analysis of the surface of the nanofibers demonstrates the presence of homogeneously blended CPSA-PAni. Most importantly, a four-point probe analysis reveals that electrical properties are maintained in the nanofibers where the conductivity is significantly increased from 0.0015 to 0.0138 S x cm(-1) when the nanofibers are prepared with 30% CPSA-PAni. The cell adhesion tests using human dermal fibroblasts, NIH-3T3 fibroblasts, and C2C12 myoblasts demonstrate significantly higher adhesion on the CPSA-PAni/PLCL nanofibers than pure PLCL nanofibers. In addition, the growth of NIH-3T3 fibroblasts is enhanced under the stimulation of various direct current flows. The CPSA-PAni/PLCL nanofibers with electrically conductive properties may potentially be used as a platform substrate to study the effect of electrical signals on cell activities and to direct desirable cell function for tissue engineering applications.

In Vitro Osteogenic Differentiation of Human Mesenchymal Stem Cells and In Vivo Bone Formation in Composite Nanofiber Meshes

Tissue engineering has become an alternative method to traditional surgical treatments for the repair of bone defects, and an appropriate scaffold supporting bone formation is a key element in this approach. In the present study, nanofibrous organic and inorganic composite scaffolds containing nano-sized demineralized bone powders (DBPs) with biodegradable poly(L-lactide) (PLA) were developed using an electrospinning process for engineering bone. To assess their biocompatibility, in vitro osteogenic differentiation of human mandible-derived mesenchymal stem cells (hMSCs) cultured on PLA or PLA/DBP composite nanofiber scaffolds were examined. The mineralization of hMSCs cultured with osteogenic supplements on the PLA/DBP nanofiber scaffolds was remarkably greater than on the PLA nanofiber scaffold during the first 14 days of culture but reached the same level after 21 days. The in vivo osteoconductive effect of PLA/DBP nanofibrous scaffolds was further investigated using rats with critical-sized skull defects. Micro-computerized tomography revealed that a greater amount of newly formed bone extended across the defect area in PLA/DBP scaffolds than in the nonimplant and PLA scaffolds 12 weeks after implantation and that the defect size was almost 90% smaller. Therefore, PLA/DBP composite nanofiber scaffolds may serve as a favorable matrix for the regeneration of bone tissue.

Nanofibrous Poly(lactic acid)/Hydroxyapatite Composite Scaffolds for Guided Tissue Regeneration

The production of nanofibrous PLA/HA composite scaffolds is described. The morphological, mechanical, surface, and thermal properties of the composites were extensively investigated. The results show that the mixture of PLA and HA formed smooth nanofibers without lumps. The incorporation of HA increased the mechanical strength of the nanofibers and changed the morphology, increasing the mean fiber diameter and pore size. Surface and internal properties confirmed that HA was homogeneously distributed inside the nanofibers and oriented towards their surface. The nanofiber composites allowed the adhesion and proliferation of pre-osteoblasts for up to 3 weeks.

Electrospun gelatin/poly(L-lactide-co-ε-caprolactone) nanofibers for mechanically functional tissue-engineering scaffolds

Recently, much attention has been given to the fabrication of tissue-engineering scaffolds with nano-scaled structure to stimulate cell adhesion and proliferation in a microenvironment similar to the natural extracellular matrix milieu. In the present study, blends of gelatin and poly(L-lactide-co-ε-caprolactone) (PLCL) (blending ratio: 0, 30, 70 and 100 wt% gelatin to PLCL) were electrospun to prepare nano-structured non-woven fibers for the development of mechanically functional engineered skin grafts. The resulting nanofibers demonstrated the uniform and smooth fibers with mean diameters ranging from approx. 50 to 500 nm with interconnected pores, regardless of the composition. The contact angle decreased with increasing amount of gelatin in the blend and the water content of the nanofibers increased concurrently. PLCL nanofibers retained significant levels of recovery following application of uniaxial stress; GP-3 with 70% PLCL blend returned to the original length within less than 10% of deformation following 200% of uniaxial elongation. The overall tensile strength was inversely affected by increase in the gelatin content and degradation rates of the nanofibers were accelerated as the gelatin concentration increased. When seeded with human primary dermal fibroblasts and keratinocytes on the nanofibers, both initial cell adhesion and proliferation rate increased as a function of the gelatin content in the blend. Additionally, the total cell number was significantly greater on the nanofiber scaffolds than on polymer-coated glasses, indicating that nanofibrous structure facilitates cell proliferation. Taken together, gelatin/PLCL blend nanofiber scaffolds may serve as a promising artificial extracellular matrix for regeneration of mechanically functional skin tissue.

Modulation of Osteogenic Differentiation of Human Mesenchymal Stem Cells by Poly[(L-lactide)-co-(ε-caprolactone)]/Gelatin Nanofibers

Developing biomaterial scaffolds to elicit specific cell responses is important in many tissue engineering applications. We hypothesized that the chemical composition of the scaffold may be a key determinant for the effective induction of differentiation in human mesenchymal stem cells (hMSCs). In this study, electrospun nanofibers with different chemical compositions were fabricated using poly[(L-lactide)-co-(epsilon-caprolactone)] (PLCL) and gelatin. Scanning electron microscopy (SEM) images showed a randomly arranged structure of nanofibers with diameters ranging from 400 nm to 600 nm. The incorporation of gelatin in the nanofibers stimulated the adhesion and osteogenic differentiation of hMSCs. For example, the well-stretched and polygonal morphology of hMSCs was observed on the gelatin-containing nanofibers, while the cells cultured on the PLCL nanofibers were contracted. The DNA content and alkaline phosphatase activity were significantly increased on the PLCL/gelatin blended nanofibers. Expression of osteogenic genes including alkaline phosphatase (ALP), osteocalcin (OCN), and collagen type I-alpha2 (Col I-alpha2) were also upregulated in cells cultured on nanofibers with gelatin. Mineralization of hMSCs was analyzed by von Kossa staining and the amount of calcium was significantly enhanced on the gelatin-incorporated nanofibers. These results suggest that the chemical composition of the underlying scaffolds play a key role in regulating the osteogenic differentiation of hMSCs.

Electroactive Electrospun Polyaniline/Poly[(L-lactide)-co-(ε-caprolactone)] Fibers for Control of Neural Cell Function

Blends of PAni and PLCL are electrospun to prepare uniform fibers for the development of electrically conductive, engineered nerve grafts. PC12 cell viability is significantly higher on RPACL fibers than on PLCL-only fibers, and the electrical conductivity of the fibers affects the differentiation of PC12 cells; the number of cells positively-stained and their expression level are significantly higher on RPACL fibers. PC12 cell bodies display an oriented morphology with outgrowing neurites. On RPACL fibers, the expression level of paxillin, cdc-42, and rac is positively affected and proteins including RhoA and ERK exist as more activated state. These results suggest that electroactive fibers may hold promise as a guidance scaffold for neuronal tissue engineering.

Synergistic Effect of Dual‐Functionalized Fibrous Scaffold with BCP and RGD Containing Peptide for Improved Osteogenic Differentiation

Over the last decade, bone tissue engineering scaffolds have been advanced owing to the bioceramic incorporation and biomimetic modification. In this report, a dual-functional fibrous scaffold with a bioceramic and biomolecule is developed, and a combined effect of a dual-modification is investigated. Biphasic calcium phosphate (BCP) is incorporated in electrospun poly (L-lactide) scaffolds, and Arg-Gly-Asp (RGD) peptide is then conjugated through the graft polymerization of acrylic acid by γ-ray irradiation. The scaffolds exhibit the intrinsic properties of BCP as well as RGD peptide, and only RGD peptide improves an adhesion and proliferation of the human mesenchymal stem cell. However, alkaline phosphatase activity and calcium formation are synergistically improved by the BCP and RGD peptide indicating that a favorable microenvironment is constructed for bone formation. Therefore, this combination strategy with bioceramic and biomolecule can be a useful tool for the bone tissue engineering.

Tissue Engineering Using a Cyclic Strain Bioreactor and Gelatin/PLCL Scaffolds

ConclusionsIn this study, we demonstrate that cyclic strain increased the proliferation of HDFs and subsequent expression of ECM proteins. Specifically, HDFs engineered under the cyclic stretching exhibited higher proliferation and up-regulated expression of collagen type IV and fibronectin. These cellular features could allow the engineered HDF tissues to exhibit contractile functions. Future studies will examine dose-dependent responses of various skin cells cultured in nanofibrous scaffold under mechanical loading that vary in strain amplitude, rate, frequency, and duration.