Phosphorylation of chitosan to improve osteoinduction of chitosan/xanthan-based scaffolds for periosteal tissue engineering.

The periosteum is a membrane that surrounds bones, providing essential cellular and biological components for fracture healing and bone repair. Tissue engineered scaffolds able to function as periosteum substitutes can significantly improve bone regeneration in severely injured tissues. Efforts to develop more bioactive and tunable periosteal substitutes are required to improve the success of this tissue engineering approach. In this work, a chemical modification was performed in chitosan, a polysaccharide with osteoconductive properties, by introducing phosphate groups to its structure. The phosphorylated polymer (Chp) was used to produce chitosan-xanthan-based scaffolds for periosteal tissue engineering. Porous and mechanically reinforced matrices were obtained with addition of the surfactant Kolliphor® P188 and the silicone rubber Silpuran® 2130A/B. Scaffolds properties, such as large pore sizes (850-1097 μm), micro-roughness and thickness (0.7-3.5 mm in culture medium), as well as low thrombogenicity compared to standard implantable materials, extended degradation time and negligible cytotoxicity, enable their application as periosteum substitutes. Moreover, the higher adsorption of bone morphogenetic protein mimic (cytochrome C) by Chp-based formulations suggests improved osteoinductivity of these materials, indicating that, when used in vivo, the material would be able to concentrate native BMPs and induce osteogenesis. The scaffolds produced were not toxic to adipose tissue-derived stem cells, however, cell adhesion and proliferation on the scaffolds surfaces can be still further improved. The mineralization observed on the surface of all formulations indicates that the materials studied have promising characteristics for the application in bone regeneration.