Multifunctional marine polysaccharide κ-carrageenan reinforced Sr–Mg hydroxyapatite/chitosan nanocomposite for bone repair applications

In order to achieve bone tissue engineering, scaffolds with a biomimetic composition are desired that mimic the composition of the original extracellular matrix and promote osteogenesis and redox balance. In this study, a new marine polysaccharide-based nanocomposite (MPKC@SMHA-CH) was synthesized by co-precipitation method, which is a κ-carrageenan (κ-Car) functionalized strontium-magnesium substituted hydroxyapatite-chitosan (SMHA-CH). The results from the physicochemical assessment (FTIR, XRD, SEM-EDAX) confirmed the successful incorporation of MPKC into the SMHA-CH matrix, enhancement of the crystallinity modulation, and porous morphology to facilitate cell infiltration. Biocompatibility and osteogenic potential were evaluated in MG-63 osteoblast-like cells after 1, 3 and 7 days. MTT experiment showed that the concentration was concentration-dependent on cytocompatibility (25-100 μg/mL) and MPKC@SMHA-CH significantly improved cell viability compared to SMHA and SMHA-CH confirmed by fluorescence labelling (Calcein-AM/PI and DAPI). Importantly, MPKC significantly reduced the level of ROS in the cells and maintained the mitochondrial membrane potential (MMP), indicating its cytoprotective activity against oxidative stress. In osteogenic differentiation experiments, the MPKC@SMHA-CH significantly promoted the early-stage alkaline phosphatase (ALP) activity and the extracellular matrix mineralization was evidenced by the strong Alizarin Red S (ARS) staining on day 7. The results suggest that the synergy of marine polysaccharides and ion-substituted hydroxyapatite and chitosan stimulates osteoblasts activity by redox regulation and maintenance of the mitochondria. The combination of MPKC@SMHA-CH forms an encouraging multifunctional nanocomposite for bone tissue engineering which, besides its structural biomimicry, enhance the biological efficacy.