Bone grafting utilises tissue harvesting from second anatomic location of same patient (autograft) or from a human donor (allograft) to treat bone defects. Limited availability of bone grafts, donor site morbidity and risk of disease transmission led to an alternative strategy for bone grafting as synthetic materials that can promote bone regeneration. Engineered bone grafts are biocompatible and possess sufficient mechanical strength to support fractured bone. Polymer scaffolds lack mechanical stability whereas ceramic scaffolds are stiffer resulting in loosening of implants. Combining polymer and ceramic to form scaffolds can enhance the physical and mechanical properties and can be used for bone tissue engineering. We hypothesised that the nucleation of hydroxyapatite in carboxymethyl cellulose (CMC) matrix would improve scaffold properties physically and mechanically; thus, demonstrating CMC based biomimetic process to synthesise novel CMC/ HA scaffolds with suitable physical, mechanical and biological properties for bone tissue engineering.

CMC/ HA scaffolds were synthesized by in situmethod at room temperature (RT) and 60°C and are labelled as CHRT and CH60 respectively, keeping the molar ratio of Ca/P as constant ∼1.6. The nucleation of hydroxyapatite (HA) from calcium chloride (CaCl₂) and sodium dihydrogen phosphate (NaH₂PO₄) was initiated inside carboxymethyl cellulose (CMC). CaCl₂solution was introduced gently in aqueous solution of CMC, thereafter; NaH₂PO₄solution was added dropwise and the mixture was stirred vigorously, kept overnight for aging at RT to obtain milky white slurry. The slurry was washed with distilled water to neutralize, cast into moulds and dried in hot air oven for 72 h to obtain scaffolds. Scanning electron microscopy (SEM) was performed to determine the surface topography of the scaffolds. Mechanical properties were tested with Universal Testing Machine (UTM) and cytotoxicity was performed by MTT assay using fibroblast cells (NIH 3T3).

SEM images shows that HA aggregates like beads and knitted orderly over CMC backbone. There is an increase in HA agglomerates and decrease in bead size with increase in synthesis temperature from RT to 60°C. Scaffolds synthesized at 60°C show enhanced mechanical properties. Compressive strength of CHRT and CH60 are 0.68 MPa and 0.9 MPa respectively and compressive moduli of CHRT and CH60 are 33 MPa and 69 MPa respectively. MTT assay confirmed proliferation of fibroblast cells, hence; proved the non-toxic nature of the scaffolds. MTT assay reveals the cell viability (cell exoskeleton) on the scaffolds after 24 h incubation.

In this study, CMC/ HA scaffolds were synthesised by in situmethod at RT and 60°C. Enhanced mechanical properties and cytocompatibility reveal the potentiality of the scaffolds for bone tissue engineering purposes.