Metal organic frameworks as a compatible reinforcement in a biopolymer bone scaffold
The insufficient mechanical strength and slow degradation rate of poly-L-lactic acid (PLLA) limit its applications in bone repair. In this study, zeolitic imidazolate framework-8 (ZIF-8), one typical metal organic framework, was introduced into a laser-sintered PLLA scaffold. The results showed that the ZIF-8 formed favorable interface bonding with PLLA due to its inherent hydrophobicity and abundant organic ligands. Meanwhile, it served as an efficient nucleating site and increased the crystallinity of PLLA. Thus, the tensile and compressive strength was improved by 36.9% and 85.6%, respectively. On the other hand, ZIF-8 was biodegradable and its degradation rate would speed up in an acid environment caused by the degradation of PLLA. In this condition, numerous cavities resulting from the degradation of ZIF-8 on the scaffold surface promoted the invasion of the immersion solution, which considerably enhanced the degradation rate. Besides, ZIF-8 released nutrient Zn element during degradation, which favored cell adhesion, proliferation and differentiation. It was suggested that the scaffold showed great potential as a candidate for bone implantation.