ABSTRACT
The 3D reconstruction of 100 µm- and 600 µm-thick fibrous poly-L/L-lactide scaffolds was performed by confocal laser scanning microscopy and supported by scanning electron microscopy and showed that the density of the fibers on the side adjacent to the electrode is higher, which can affect cell diffusion, while the pore size is generally the same. Bone marrow mesenchymal stem cells cultured in a 600 µm-thick scaffold formed colonies and produced conditions for cell differentiation. An in vitro study of stem cells after 7 days revealed that cell proliferation and hepatocyte growth factor release in the 600 µm-thick scaffold were higher than in the 100 µm-thick scaffold. An in vivo study of scaffolds with and without stem cells implanted subcutaneously onto the backs of recipient mice was carried out to test their biodegradation and biocompatibility over a 0-3-week period. The cells seeded onto the 600 µm-thick scaffold promoted significant neovascularization in vivo. After 3 weeks, a significant number of donor cells persisted only on the inside of the 600 µm-thick scaffold. Thus, the use of bulkier matrices allows to prolong the effect of secretion of growth factors by stem cells during implantation. These 600 µm-thick scaffolds could potentially be utilized to repair and regenerate injuries with stem cell co-culture for vascularization of implant.
ABSTRACT
Chitosan coatings of biological heart-valve prostheses enhance their biocompatibility, resistance to pathogenic microflora and lifetime. Collagen tissues can be coated with chitosan in aqueous solution acidified, to make chitosan soluble, with H2CO3 formed from a coexisting liquid CO2 phase under pressure. The advantage of H2CO3 is that it can be easily removed after the coating procedure. This study assessed the effects of 6-50â¯MPa CO2 pressure during the coating procedure on the structure and mechanical properties of the resulting biocomposite matrices. The dependence of chitosan adsorption on CO2 pressure was bell-shaped, reaching a maximum adsorption of 0.8 mass % at 40â¯MPa. Tissue surface became highly porous upon pressure treatment. At 50â¯MPa, the pores merged to form furrows with lengths of several hundred micrometers, accompanied by collagen fibril reorganisation. Chitosan coating did not affect tissue tensile strength in the axial direction, but increased it by 75% in the radial direction in the tissue coated at 50â¯MPa pressure. Strain at break, a measure of elasticity, increased in both directions by up to 100% upon coating with chitosan. CO2 pressure of 30-50â¯MPa seems thus optimal in terms of chitosan incorporation and tissue mechanical properties.
