Development and in vitro assessment of a bi-layered chitosan-nano-hydroxyapatite osteochondral scaffold.

An innovative approach was developed to engineer a multi-layered chitosan scaffold for osteochondral defect repair. A combination of freeze drying and porogen-leaching out methods produced a porous, bioresorbable scaffold with a distinct gradient of pore size (mean = 160-275 µm). Incorporation of 70 wt% nano-hydroxyapatite (nHA) provided additional strength to the bone-like layer. The scaffold showed instantaneous mechanical recovery under compressive loading and did not delaminate under tensile loading. The scaffold supported the attachment and proliferation of human mesenchymal stem cells (MSCs), with typical adherent cell morphology found on the bone layer compared to a rounded cell morphology on the chondrogenic layer. Osteogenic and chondrogenic differentiation of MSCs preferentially occurred in selected layers of the scaffold in vitro, driven by the distinct pore gradient and material composition. This scaffold is a suitable candidate for minimally invasive arthroscopic delivery in the clinic with potential to regenerate damaged cartilage and bone.

Structural, mechanical and swelling characteristics of 3D scaffolds from chitosan-agarose blends.

This study aimed to explore the correlation between mechanical and structural properties of chitosan-agarose blend (Ch-Agrs) scaffolds. Porosity of Ch-Agrs scaffolds was constant at 93%, whilst pore sizes varied between 150 and 550 µm. Pore sizes of the blend scaffolds (150-300 µm) were significantly smaller than for either agarose or chitosan scaffolds alone (ca. 500 µm). Ch50-Agrs50 blend scaffold showed the highest compressive modulus and strength values (4.5 ± 0.4 and 0.35 ± 0.03 MPa) due to reduction in the pore size. The presence of agarose improved the stability of the blends in aqueous media. The increase in compressive properties and residual weight after the TGA test, combined with the reduction in the swelling percentage of the blend scaffolds suggested an interaction between chitosan and agarose via hydrogen bonding which was confirmed using FTIR analysis. All wet blend scaffolds exhibited instant recovery after full compression. This study shows the potential of Ch-Agrs scaffolds for repairing soft tissue.