A novel bilayer osteochondral scaffold integrating Hofmeister-treated PVA-based hydrogel with collagen-coated PCL...

Osteochondral tissue engineering is promising but challenging, because an effective scaffold must present gradient properties that match heterogeneous osteochondral tissue while providing sufficient mechanical support for post-implantation loading. Herein, a novel bilayer scaffold was fabricated based on poly(vinyl alcohol) (PVA) and polycaprolactone (PCL). The bone-layer scaffold was prepared by sintering PCL microspheres, followed by a type I collagen coating to improve cell attachment without compromising its porosity. FTIR, SEM, and EDS confirmed successful uniform collagen coating. The cartilage-layer scaffold was produced from a freeze-thawed PVA-based hydrogel. The addition of 1.5% w/v alginate to PVA (10% w/v) increased the hydrogel pore size from 1.26 ± 0.46 μm to 11.95 ± 4.05 μm and the compressive modulus from 36 ± 3 kPa to 49 ± 5 kPa. Hofmeister treatment of the PVA-alginate hydrogels with a 1.5 M sodium sulfate solution significantly increased the compressive modulus from 49 ± 5 kPa to 190 ± 29 kPa, approaching native articular cartilage, without reducing the pore size significantly (10.08 ± 3.89 μm). The resulting hydrogel also showed a high water content but anti-swelling behavior. MTT assays confirmed that all the scaffolds supported cell proliferation, and SEM revealed a well-spread mesenchymal stem cell morphology on the bone-layer scaffold and a poorly spread, chondrocyte-like morphology on the cartilage-layer scaffolds. Overall, based on the physicochemical and biological characterization, the fabricated bilayer scaffold shows promising features for potential use in osteochondral tissue engineering.