Degradation mechanisms and acceleration strategies of poly (lactic acid) scaffold for bone regeneration

Poly (lactic acid) (PLA) with good biodegradability, biocompatibility and processability has a wide application prospect in bone tissue engineering. However, PLA exhibits a very slow degradation rate, hindering the regeneration of new bone. In this study, the degradation mechanisms of PLA bone scaffold, including autocatalysis and non-catalysis, end-chain and random chain breaking, surface degradation and bulk degradation, were analyzed systematically, and the influence factors including crystallinity, molecular weight, pH, and so on, were introduced. On this basis, the strategies including blending, copolymerization, compounding and surface modification to accelerate the degradation of PLA were summarized, and the accelerating mechanisms were analyzed and discussed detailedly. In addition, rapid prototyping technologies with unique advantages on the structure and shape of scaffold were introduced. The mechanical properties (strength and modulus) and biological properties (in vivo and in vitro) of PLA scaffold were reviewed and discussed. Finally, the present problem of research including the simultaneous improvement of mechanical and degradation properties was put forward, and four-dimensional printing (4D printing) as an advanced technique which might bring new ideas to improve and extend the properties of PLA scaffold was mentioned.