Hydroxypropyl methylcellulose-controlled in vitro calcium phosphate biomineralization

Dicalcium phosphate dihydrate (DCPD) and octacalcium phosphate (OCP) particles have been widely recognized as precursors for synthesizing hydroxyapatite (HAp), the main mineral found in bone tissues. In this regard, we demonstrated a novel approach for biomimicking DCPD and OCP biocomposite particles in the hydroxylpropyl methylcellulose (HPMC) biopolymer using single and double diffusion gel techniques. Hybrid biocomposite aggregates were collected and characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and scanning pyroelectric microscopy (SPEM). We also conducted density functional theory (DFT) calculations to unravel interactions among HPMC and ionic species by determining the optimized structures, bond lengths and sigma. SEM showed different morphologies of DCPD/HPMC and OCP/HPMC biocomposite particles from highly porous spheres and nano-platelets to plate-shaped biocomposites. We also demonstrated that the HPMC biopolymer was entrapped within the biocomposite particles after the demineralization process. We found that different parameters influenced the generation of calcium phosphate/HPMC biocomposites including ion concentration and the type of diffusion method. In addition, HPMC was able to change the morphology of particles from crystal shapes to porous aggregates and spheres of DCPD/HPMC and OCP/HPMC biocomposites. This study may suggest that HPMC, as a high molecular-weight polysaccharide, is a potential candidate for bone tissue regeneration.