The application of precision scaffolds combined with nanomaterials for cartilage tissue engineering

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In the first part, fused deposition manufacturing (FDM) was utilized to fabricate the precision scaffolds for cartilage and bone regeneration. The results indicated that the highly porous and interconnected structure of precision scaffolds could benefit chondrocytes and osteoblasts ingrowth. Chondrocyte proliferated well with matrix accumulation in precision scaffolds coated with type II collagen at four weeks of in vitro culture. Based on the results of first part, highly porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds modified by type II collagen for cartilage tissue engineering were fabricated in the second part. The scaffolds were seeded with porcine articular chondrocytes and cultured for 4 weeks. Although the cells were well distributed in the interior of the constructs with a large fiber interval and formed neocartilage around, the acidic degradation products of PLGA may have influenced cell growth. The study also suggested that a low processing temperature may be required to produce PLGA precision scaffolds using FDM. Therefore, the liquid-frozen deposition manufacturing (LFDM) system based on an improvement of the FDM process was developed. PLGA precision scaffolds were fabricated by LFDM from the PLGA solution of different concentrations. LFDM scaffolds in general had mechanical strength better matched to that of the native cartilage, compared to FDM scaffolds. Chondrocytes in LFDM scaffolds made from low concentrations (15-20%) of PLGA solution maintained the round shape, well proliferated and secreted abundant extracellular matrix. Furthermore, neocartilage formation was observed in LFDM scaffolds seeded with porcine articular chondrocytes after 28 days of culture. The LFDM system successfully offered a useful way to fabricate scaffolds for cartilage tissue engineering applications. On the other hand, the nanocomposites (denoted “CII-Au”) of porcine type II collagen (CII) with 0.05%, 0.1%, 0.5%, 1% or 2.5% (w/w) gold nanoparticles (~5 nm), were fabricated for potential use in cartilage tissue engineering. The addition of gold at low concentrations (≦0.5%) increased the modulus and viscosity as well as the free radical scavenging ability. Chondrocytes proliferation on CII-Au 0.1% was promoted. Type I collagen, aggrecan and Sox 9 gene expressions increased with the increased Au content, but slightly decreased at 2.5% Au. Au at an appropriate amount could be well dispersed in CII, and enhanced the material modulus, antioxidant effect, as well as the chondrocyte growth and matrix production. Furthermore, cytotoxicity and immunological response of gold and silver nanoparticles with various sizes were evaluated by using a murine macrophage cell line. The results showed the cell proliferation for treatment with nanoparticles at a concentration of 10 ppm decreased dramatically in both nanoparticles. Gold nanoparticles had greater effect of cytotoxicity and proinflammatory genes expression (IL-1, IL-6 and TNF-a)than silver nanoparticles in the same size. These results were speculated that gold nanoparticles were easily adsorbed by the nonspecific serum proteins due to negative surface charge and induced different endocytosis pathway.