Degradation and osteogenic potential of a novel poly(lactic acid)/nano-sized β-tricalcium phosphate scaffold

Lu Cao,^1,2 Ping-Guo Duan,^1,2 Hui-Ren Wang,^1,2 Xi-Lei Li,^1,2 Feng-Lai Yuan,³ Zhong-Yong Fan,⁴ Su-Ming Li,⁵ Jian Dong<sup>1,2

1</sup>Department of Orthopedic Surgery, Zhongshan Hospital, Fudan University, Shanghai, China; ²State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai, China; ³Affiliated Third Hospital of Nantong University, Wuxi, Jiangsu, China; ⁴Department of Materials Science, Fudan University, Shanghai, China; ⁵Max Mousseron Institute on Biomolecules, Montpellier I University, Montpellier, France

Abstract: The purpose of this study was to investigate the influence of nano-sized β-tricalcium phosphate (β-TCP) on the biological performance of poly (lactic acid) (PLA) composite scaffolds by using in vitro degradation and an in vivo model of heterotopic bone formation. Nano-sized βTCP (nβ-TCP) was prepared with a wet grinding method from micro-sized β-TCP (mβ-TCP), and composite scaffolds containing 0, 10, 30, or 50 wt% nβ-TCP or 30 wt% mβ -TCP were generated using a freeze-drying method. Degradation was assessed by monitoring changes in microstructure, pH, weight, and compressive strength over a 26-week period of hydrolysis. Composite scaffolds were processed into blocks, and implanted into muscular pockets of rabbits after loading with recombinant human bone morphogenetic protein-2 (rhBMP-2). New bone formation was evaluated based on histological and immunohistochemical analysis 2, 4, and 8 weeks after implantation. The in vitro results indicated that the buffering effect of nβ-TCP was stronger than mβ-TCP, which was positively correlated with the content of nβ-TCP. The in vivo findings demonstrated that nβ-TCP enhanced the osteoconductivity of the scaffolds. Although composite scaffolds containing 30% nβ-TCP exhibited similar osteoconductivity to 50% nβ-TCP, they had better mechanical properties than the 50% nβ-TCP scaffolds. This study supports the potential application of a composite scaffold containing 30% nβ-TCP as a promising scaffold for bone regeneration.

Keywords: poly (lactic acid), β-tricalcium phosphate, biodegradation, porous scaffold, bone regeneration