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Bone defect repair poses significant challenges in orthopedics, thereby increasing the demand for bone substitutes. Magnesium phosphate cements (MPCs) are widely used for bone defect repair because of their excellent mechanical properties and biodegradability. However, high crystallinity and uncontrolled magnesium ion (Mg2+) release limit the surface bioactivity of MPCs in bone regeneration. Here, we fabricate chondroitin sulfate (CS) as a surface coating via the lyophilization method, namely CMPC. We find that the CS coating is uniformly distributed and improves the mechanical properties of MPC through anionic electrostatic adsorption, while mediating degradation-related controlled ion release of Mg2+. Using a combination of in vitro and in vivo analyses, we show that the CS coating maintained cytocompatibility while increasing the cell adhesion area of MC3T3-E1s. Furthermore, we display accelerated osteogenesis and angiogenesis of CMPC, which are related to appropriate ion concentration of Mg2+. Our findings reveal that the preparation of a lyophilized CS coating is an effective method to promote surface bioactivity and mediate Mg2+ concentration dependent osteogenesis and angiogenesis, which have great potential in bone regeneration. [ABSTRACT FROM AUTHOR]

Incorporating bioactive substances into synthetic bioceramic scaffolds is challenging. In this work, oxygen-carboxymethyl chitosan (O-CMC), a natural biopolymer that is nontoxic, biodegradable and biocompatible, was introduced into magnesium potassium phosphate cement (K-struvite) to enhance its mechanical properties and cytocompatibility. This study aimed to develop O-CMC/magnesium potassium phosphate composite bone cement (OMPC), thereby combining the optimum bioactivity of O-CMC with the extraordinary self-setting properties and mechanical intensity of the K-struvite. Our results indicated that O-CMC incorporation increased the compressive strength and setting time of K-struvite and decreased its porosity and pH value. Furthermore, OMPC scaffolds remarkably improved the proliferation, adhesion and osteogenesis related differentiation of MC3T3-E1 cells. Therefore, O-CMC introduced suitable physicochemical properties to K-struvite and enhanced its cytocompatibility for use in bone regeneration. [ABSTRACT FROM AUTHOR]

Magnesium phosphate cement (MPC) can be injected to form an in situ scaffold to repair bone defects. Here we synthesized novel injectable bioactive cements (CMPCs) by incorporating different ratios of carboxymethyl chitosan (CMC, 0–10%) into MPC. The physiochemical properties, compositions, and microstructures of CMPCs were evaluated. The in vitro cellular responses of pre-osteoblast MC3T3-E1 cells to CMPCs including adhesion, proliferation, and differentiation were quantified and the underlying cellular mechanisms investigated. CMPCs had longer setting times and lower setting temperatures. CMPC injectability was enhanced by the addition of CMC. The CMPC containing 5% CMC had the highest compressive strength and washout resistance. CMPCs had a more neutral pH compared to MPC at four weeks. Furthermore, CMPC samples showed similar degradability and Mg2+ release to MPC in Tris-HCl buffer. Osteoblasts (MC3T3-E1) showed significantly greater adherence, proliferation, and differentiation on CMPC specimens than on MPC. Finally, CMPCs effectively increased the adsorption of fibronectin and activated integrin signaling as indicated by enhanced FAK and ERK phosphorylation. Our novel CMPC composites have improved physicochemical properties and cellular responses and represent a promising material for bone regeneration. • CMPCs showed superior compressive strength, injectability and washout resistance. • Osteoblast cells showed better adherence, proliferation and differentiation on CMPCs. • CMPCs increased fibronectin adsorption and activated the integrin-FAK-ERK signaling. [ABSTRACT FROM AUTHOR]