Injectable methylcellulose hydrogel containing calcium phosphate nanoparticles for bone regeneration

A novel injectable methylcellulose (MC) hydrogel containing calcium phosphate nanoparticles (CaP NPs) was prepared by an in situ formation process, in which the precursor salts induced a salt-out effect in the MC solution. The thermo-sensitive properties of MC-CaP NPs composite hydrogels with different crystalline phases were characterized by rheometry, infrared spectroscopy and injectability test. The as-prepared MC hydrogels with bioactive CaP NPs had a suitable injectability at the body temperature, irrespective of the crystalline phases of CaP NPs. At the physiological pH condition, the structure of the MC hydrogel containing CaP NPs was analyzed by scanning electron microscopy, X-ray diffraction (XRD). The XRD results indicate that the in situ synthesized CaP NPs had a crystalline phase of hydroxyapatite (HAP). The in vitro study using mesenchymal stem cells showed that MC-HAP NPs composite hydrogel was biocompatible. The in vivo study indicated that the regeneration rate of new mature bone was also higher in the MC-HAP NPs composite hydrogel than in the pure MC hydrogel. The results of this study indicate that injectable MC-HAP NPs composite hydrogel has a great potential for bone tissue regeneration.