Simple fabrication method for a porous poly(vinyl alcohol) matrix by multisolvent mixtures for an air-exposed model of the lung epithelial system.

We introduce a simple and easy method for fabricating a thin and porous matrix that can be used as an extracellular matrix (ECM). A porous poly(vinyl alcohol) (PVA) matrix was created through recrystallization by multiple solvents under distilled water (DW), isopropyl alcohol (IPA), and a combination of DW and IPA. The crysatllization was driven by precipitating and dissolving a solute in a solution of a solvent and a nonsolvent, which induced the formation of microspheres in the IPA. The crystal structure depended on the ratio of the solvent/nonsolvent and the concentration of the PVA aqueous solution; these properties were used to tune the thickness, size, and porosity of the matrices. The resulting PVA matrix was chemically stabilized through a reaction with glutaraldehyde in the IPA solution. We demonstrated that a very thin and porous PVA matrix provided an effective functional model of the lung epithelial system. Lung epithelial cells (A549) displayed a high affinity for this matrix, which was permeable to the culture medium. These properties facilitated culturing under the air environment.

Effects of pulsatile bioreactor culture on vascular smooth muscle cells seeded on electrospun poly (lactide-co-ε-caprolactone) scaffold.

Electrospun nanofibrous scaffolds have several advantages, such as an extremely high surface-to-volume ratio, tunable porosity, and malleability to conform over a wide variety of sizes and shapes. However, there are limitations to culturing the cells on the scaffold, including the inability of the cells to infiltrate because of the scaffold's nano-sized pores. To overcome the limitations, we developed a controlled pulsatile bioreactor that produces static and dynamic flow, which improves transfer of such nutrients and oxygen, and a tubular-shaped vascular graft using cell matrix engineering. Electrospun scaffolds were seeded with smooth muscle cells (SMCs), cultured under dynamic or static conditions for 14 days, and analyzed. Mechanical examination revealed higher burst strength in the vascular grafts cultured under dynamic conditions than under static conditions. Also, immunohistology stain for alpa smooth muscle actin showed the difference of SMC distribution and existence on the scaffold between the static and dynamic culture conditions. The higher proliferation rate of SMCs in dynamic culture rather than static culture could be explained by the design of the bioreactor which mimics the physical environment such as media flow and pressure through the lumen of the construct. This supports regulation of collagen and leads to a significant increase in tensile strength of the engineered tissues. These results showed that the SMCs/electrospinning poly (lactide-co-ε-caprolactone) scaffold constructs formed tubular-shaped vascular grafts and could be useful in vascular tissue engineering.

Preparation of lotus-leaf-like structured blood compatible poly(ε-caprolactone)-block-poly(L-lactic acid) copolymer film surfaces.

Lotus-leaf-like structured poly(ε-caprolactone)-block-poly(L-lactic acid) copolymer (PCL-b-PLLA) films cast using the solvent-nonsolvent casting method. PCL-b-PLLA was synthesized by the well-known copolymerization process, and was confirmed by (1)H NMR analysis. The molecular weight of the synthesized PCL-b-PLLA was measured by gel permeation chromatography (GPC). The number-average (Mn), weight-average (Mw) molecular weights and polydispersity (Mw/Mn) were 3.9×10(4), 5.1×10(4), and 1.3, respectively. PCL-b-PLLA films were cast in vacuum conditions with various nonsolvent ratios. Tetrahydrofuran (THF) was used as solvent and ethanol was used as nonsolvent. Surface hydrophobicity was confirmed by the water contact angle. The water contact angle was increased from 90.9°±4.2° to 130.2°±3.6°. Water contact angle was found to be influenced by surface topography. The prepared film surfaces were characterized by scanning electron microscopy (SEM). Changes in crystalline property were characterized by X-ray diffraction (XRD). Platelet adhesion tests of the modified PCL-b-PLLA film surfaces were evaluated by platelet-rich plasma (PRP) and whole blood. Cell adhesive behavior on the modified film surfaces was evaluated by fibroblast cell culture. The prepared lotus-leaf-like structured film surfaces exhibited reduced platelet adhesion and an increased fibroblast cell proliferation ratio.

Three-dimensional electrospun poly(lactide-co-ɛ-caprolactone) for small-diameter vascular grafts.

Nanofibers have been applied to tissue engineering scaffolds because fiber diameters are of the same scale as the physical structure of protein fibrils in the native extracellular matrix. In this study, we utilized cell matrix engineering combined with cell sheet matrix and electrospinning technologies. We studied small-diameter vascular grafts in vitro by seeding smooth muscle cells onto electrospun poly(lactide-co-ɛ-caprolactone) (PLCL) scaffolds, culturing and constructing a three-dimensional network. The vascular grafts constructed using cell matrix engineering were similar to the native vessels in their mechanical properties, such as tensile strength, tensile strain, and e-modulus. Also, they had a self-sealing property more improved than GORE-TEX because PLCL has compatible elasticity. Small-diameter vascular grafts constructed using matrix engineering have the potential to be suitable for vascular grafts.