Fabrication of composition-graded collagen/chitosan–polylactide scaffolds with gradient architecture and properties

Chitosan–polylactide (CH–PLA) copolymers with various polylactide percentages changing from around 14 to 40   wt% were synthesized. CH–PLAs were then blended with type-II collagen to fabricate layered collagen/CH–PLA scaffolds that are potentially suitable for the applications in articular cartilage repair. Based on combinatorial processing techniques involving layer-superposition, thermal melting and freeze-drying, two types of stratified collagen/CH–PLA scaffolds were built. The content of collagen inside the scaffolds altered from the top layer to the bottom layer in a trend contrary to that of chitosan. One of them was fabricated using tripolyphosphate (TPP) as a single crosslinker and another type of scaffold was constructed via a dual-crosslinking pathway using TPP and genipin as two crosslinkers in a designated order. These collagen/CH–PLA scaffolds were found to have graded average pore-size and porosity, gradient swelling index and layer-dependent compressive modulus. The resulting scaffolds were thus partially similar to the articular cartilage extracellular matrix in composition , structure and property. In vitro cell culture on some optimized collagen/CH–PLA scaffolds for a period of time up to 3   weeks showed that the scaffolds were able to well support the growth of the seeded cells, suggesting that these collagen/CH–PLA scaffolds have promising potential for articular cartilage repair.