Core–shell-Structured ZIF-8@PDA-HA with Controllable Zinc Ion Release and Superior Bioactivity for Improving a Poly-l-lactic Acid Scaffold

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are able to act as effective reinforcements to enhance the overall performance of a poly-l-lactic acid (PLLA) scaffold due to its interface compatibility and natural degradability. Nevertheless, the fast degradation of ZIF-8 would release excessive zinc ions, which produces adverse effects on natural cell growth. In this study, a core–shell-structured nanoparticle, in which ZIF served as a core and hydroxyapatite (HA) served as a shell, was constructed by polydopamine (PDA)-induced in situ growth of HA on ZIF-8 nanoparticles, aiming to control the zinc ion release. Then, the core–shell-structured nanoparticle (ZIF-8@PDA-HA) was introduced into the PLLA scaffold using selective laser sintering. Results showed that the zinc ion concentration for the PLLA/ZIF-8@PDA-HA scaffold decreased by 65.3% after 28 days of immersion, as compared with the PLLA/ZIF-8 scaffold. Moreover, the in situ-synthesized HA possessed superior bioactivity, which effectively enhanced the mineralization ability of scaffolds and promoted cell adhesion, proliferation, and differentiation.