No abstract

Polymer porous scaffolds and hydrogels have been separately employed as analogues of the native extra-cellular matrix (ECM). However, both of these two kinds of materials have their own advantages and shortcomings. In this work, an attempt to combine the advantages of these two kinds of materials is carried out. Poly-L-lactide (PLLA) scaffolds with good mechanical properties were prepared by thermally induced phase separation, which were then filled with hydrogel aiming at entrapment of cells within a support of predefined shape. Agar, which has a function to promote chondrogenesis, was selected to entrap chondrocytes, acting as analogues of native ECM. A straight forward merit of this construct is that both mechanical strength and macroscopic shape, and analogous ECM can be simultaneously achieved. The morphology and distribution of the chondrocytes were studied by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The cell growth behaviors were determined by MTT assay and collagen and glycosaminoglycan (GAG) secretion. After culture for 7 and 14 days, the cells in the construct were round and surrounded by the hydrogel. The MTT viability and the cell secretion in the chondrocytes/agar/scaffold construct were also higher than that of the chondrocytes/scaffold construct (control). Gelatin was further introduced into the construct, yielding improved GAG secretion and cytoviability. After implantation in the subcutaneous dorsum of nude mice for 4 weeks, cartilage-like specimens maintaining their original rectangular shapes were harvested. Histological examination showed that new cartilage was regenerated and a large quantity of collagen and GAG were secreted, while the cells in the control PLLA scaffold turned to be fibroblast-like with less secretion of extracellular matrices. The method provides a useful pathway of scaffold preparation and cell transplantation, which can achieve suitable mechanical properties and good cell performance simultaneously.

Biodegradable poly(l-lactide) (PLLA) scaffolds with well-controlled interconnected irregular pores were fabricated by a porogen leaching technique using gelatin particles as the porogen. The gelatin particles (280 -450 m) were bonded together through a treatment in a saturated water vapor condition at 70°C to form a 3-dimensional assembly in a mold. PLLA was dissolved in dioxane and was cast onto the gelatin assembly. The mixtures were then freeze-dried or dried at room temperature, followed by removal of the gelatin particles to yield the porous scaffolds. The microstructure of the scaffolds was characterized by scanning electron microscopy with respect to the pore shape, interpore connectivity, and pore wall morphology. Compression measurements revealed that scaffolds fabricated by freeze-drying exhibited better mechanical performance than those by room temperature dying. Along with the increase of the polymer concentration, the porosity of the scaffolds decreased whereas the compressive modulus increased. When the scaffolds were in a hydrated state, the compressive modulus decreased dramatically.

Three-dimensional poly(L-lactic acid) (PLLA) scaffolds with high porosity and an average pore size of 280-450 microm were fabricated using gelatin particles as porogen. The particles were bonded together by incubation in saturated water vapor at 70 degrees C for 3.5 h. After casting the PLLA/1,4-dioxane solution, freeze-drying and porogen leaching with 70 degrees C water, a porous scaffold with well-interconnected pores and some nano-fibers was obtained. The biological performance of the scaffold was evaluated by in vitro chondrocyte culture and in vivo implantation. In comparison with the control scaffold fabricated with NaCl particles as porogen under the same conditions, the experimental scaffold had better biological performance because the gelatin molecules were stably entrapped onto the pore surfaces. A larger number of cells in the experimental scaffold were observed by confocal laser scanning microscopy after the viable cells had been stained with fluorescein diacetate. The chondrocytes showed more spreading morphology. Higher cytoviability and secretion of glycosaminoglycan (GAG) were also determined in the experimental scaffold. After implantation of the chondrocytes/PLLA scaffold construct to the subcutaneous dorsum of nude mice for 30-120 days, cartilage-like specimens were harvested. Histological examination showed that the regenerated cartilages had a large quantity of collagen and GAG.