Integrating biologically inspired nanomaterials and table-top stereolithography for 3D printed biomimetic osteochondral scaffolds

TLDR

The osteochondral interface of arthritic joints is difficult to regenerate because of its poor regenerative capacity and complex stratified architecture, and native tissue ECM contains numerous nanoscale organic and inorganic components that current scaffolds fail to mimic. This study aims to develop 3D‑printed biomimetic nanocomposite scaffolds to enhance osteochondral tissue regeneration. The authors synthesized osteoconductive nanocrystalline hydroxyapatite and PLGA nanospheres loaded with TGF‑β1, then used a tabletop stereolithography printer with a nano‑ink (nHA + nanospheres + hydrogel) to fabricate a porous, hierarchically structured scaffold with spatially and temporally controlled bioactive gradients. In vitro, the graded scaffold markedly improved human bone marrow‑derived MSC adhesion, proliferation, and osteochondral differentiation, demonstrating the efficacy of the nano‑ink and printing approach and the synergistic effect of tissue‑specific growth factors.

Abstract

The osteochondral interface of an arthritic joint is notoriously difficult to regenerate due to its extremely poor regenerative capacity and complex stratified architecture. Native osteochondral tissue extracellular matrix is composed of numerous nanoscale organic and inorganic constituents. Although various tissue engineering strategies exist in addressing osteochondral defects, limitations persist with regards to tissue scaffolding which exhibit biomimetic cues at the nano to micro scale. In an effort to address this, the current work focused on 3D printing biomimetic nanocomposite scaffolds for improved osteochondral tissue regeneration. For this purpose, two biologically-inspired nanomaterials have been synthesized consisting of (1) osteoconductive nanocrystalline hydroxyapatite (nHA) (primary inorganic component of bone) and (2) core-shell poly(lactic-co-glycolic) acid (PLGA) nanospheres encapsulated with chondrogenic transforming growth-factor β1 (TGF-β1) for sustained delivery. Then, a novel table-top stereolithography 3D printer and the nano-ink (i.e., nHA + nanosphere + hydrogel) were employed to fabricate a porous and highly interconnected osteochondral scaffold with hierarchical nano-to-micro structure and spatiotemporal bioactive factor gradients. Our results showed that human bone marrow-derived mesenchymal stem cell adhesion, proliferation, and osteochondral differentiation were greatly improved in the biomimetic graded 3D printed osteochondral construct in vitro. The current work served to illustrate the efficacy of the nano-ink and current 3D printing technology for efficient fabrication of a novel nanocomposite hydrogel scaffold. In addition, tissue-specific growth factors illustrated a synergistic effect leading to increased cell adhesion and directed stem cell differentiation.