Component effect of stem cell-loaded thermosensitive polypeptide hydrogels on cartilage repair

Publication date: Available online 21 April 2018
Source:Acta Biomaterialia
Author(s): He Liu, Yilong Cheng, Jinjin Chen, Fei Chang, Jincheng Wang, Jianxun Ding, Xuesi Chen
Biophysical properties of the desired biomimetic scaffolds, such as porosity and elasticity, have been proven associated with the efficacy of cartilage regeneration. In this work, the copolymers of poly(L-alanine)-block-poly(ethylene glycol)-block-poly(L-alanine) (PA-PEG-PA) and poly(L-alanine-co-L-phenylalanine)-block-poly(ethylene glycol)-block-poly(L-alanine-co-L-phenylalanine) (PAF-PEG-PAF) with different ratios of alanine to phenylalanine were synthesized. The introduction of a hydrophobic amino acid, phenylalanine, into polyalanine-based thermosensitive hydrogel leaded to the enhanced gelation behaviors and upregulated mechanical properties. Moreover, the increase of phenylalanine content resulted in the enlarged pore size and enhanced mechanical strength of PAF-PEG-PAF thermogel, followed by the regeneration of hyaline-like cartilage with reduced fibrous tissue formation. The findings indicated the great potential of thermosensitive polypeptide hydrogels in cartilage tissue engineering.Statement of SignificanceArticular cartilage defect has limited self-repair ability due to the lack of blood supply and innervation, which may lead to knee osteoarthritis afterwards. Injectable hydrogels are demonstrated possessing outstanding properties as biomimetic scaffolds in cartilage tissue engineering, while the effect of biophysical properties on the efficacy of cartilage regeneration has not been revealed. Herein, the poly(ethylene glycol)−polypeptide triblock copolymers with different ratios of alanine to phenylalanine were synthesized. The sol-to-gel transition temperature and the critical gelling concentration decreased as the increased amount of phenylalanine units, resulting in the enlarged pore size and enhanced mechanical strength. These features lead to better regeneration of hyaline-like cartilage with reduced fibrous tissue formation, indicating great potential of thermosensitive polypeptide hydrogels for efficient cartilage repair.

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