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Bone-Mimetic Laminated Nano-Structures for Regeneration of Skeletal Tissues

Bone exhibits hierarchical levels of organization from macroscopic to microscopic to nanoscale. The objective of this work was to develop a bonemimetic composite matrix to provide structural support to the regenerating region and to support the cascade of osteogenic differentiation of progenitor marrow stromal (BMS) cells. Sheets of poly(L-lactide) (L-PLA) nanofibers, fabricated by electrospinning, were coated with a hydrogel/apatite precursor solution, stacked and pressed together, and allowed to crosslink by photopolymerization to form a peptide-reinforced hydrogel/apatite laminated composite. Addition of an osteonectin-derived glutamic acid peptide (Glu6) and lamination resulted in an order of magnitude increase in modulus of the composite to within the range reported for wet human cancellous bone. Lamination significantly increased the extent of mineralization of BMS cells and the laminates reinforced with apatite nanocrystals and conjugated with integrin-binding focal-point adhesion RGD peptide (Lam-RGD-HA) had 3-fold higher calcium content and higher expression of osteogenic markers osteopontin and osteocalcin (compared to laminates without apatite or RGD) after 21 days of incubation in osteogenic media. Laminated osteon-mimetic structures have the potential to provide mechanical strength to the regenerating region as well as supporting the differentiation of progenitor cells to the osteogenic lineage.