Synthesis and Characterization of Chitosan-Mg-Based Composite Scaffolds for Bone Repair Applications

Abstract

Bone has a remarkable ability to regenerate and heal itself when damaged. Most minor injuries heal naturally over time, but when the defects are larger, they require a substrate to support the cell growth and guide the repair process. Bone grafting is currently done by using either an autograft, where the substrate is harvested from a suitable donor site within the patient’s body; or an allograft, where the substrate is harvested from a cadaver. However, both techniques have significant drawbacks. In autografting, significant complications tend to arise from donor site morbidity. In allografting, the issues are the risk of disease transmission, and the logistical difficulties in the local or even global matching process for donor tissue. A third approach, employing tissue-engineered scaffold materials, provides superior performance by helping to restore bone tissue functions during regeneration and by subsequent resorption of the graft material as new bone tissue forms. These bioactive scaffolds are porous and made of natural materials that are capable of harboring growth factors, drugs, genes, or stem cells. The objectives of this research are to synthesize biofunctional composite scaffold materials, based on chitosan (CS) and magnesium (Mg), for use in bone regeneration and to measure their physiochemical properties. Scaffolds were fabricated from the aqueous dispersions of starting materials by subsequent freezing and phase separation by the lyophilization process. A CS solution was prepared by dissolving CS in 2 % (v/v) acetic acid solution, whereas carboxymethyl chitosan (CMC) was dissolved in deionized water. The concentrations of CS and CMC (in a constant 1:1 weight ratio) ranged between 2% and 5 %. Various dry weight percentages of Mg gluconate (MgG) were added to the scaffolds by dissolving the MgG solution in the CS/CMC. SEM imaging showed the scaffolds to possess uniform porosity with a pore size distribution range of 100–150 μm. Micro CT analysis showed that the pores were distributed throughout the scaffold’s entire volume and they were highly interconnected. Compressive strengths of up to 340 kPa and compressive moduli of up to 5 MPa were obtained for these fabricated scaffolds. When introduced into a cell culture medium, these scaffolds were found to remain intact, retaining their original three-dimensional frameworks and ordered porous structures maintaining sufficient mechanical strength. These observations provide a new effective approach for preparing scaffold materials suitable for bone tissue engineering.