Comparison of different hydroxyapatite composites for bone tissue repair: In vitro and in vivo analyses

The material used for bone tissue repair needs to be simultaneously osteoconductive, osteoinductive, and osteogenic. To overcome this problem, researchers combine hydroxyapatite (HA) with natural materials to improve properties. This paper compares the effects of angiogenesis and osteogenesis with different composites through in vivo experiments and characterization analysis.

Chitosan/nHA (CS/nHA) and sodium alginate/nHA (SA/nHA) microspheres were synthesized via reverse-phase emulsification crosslinking and analyzed using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD). Implanted into mouse thigh muscles, their angiogenic and osteogenic potentials were assessed after 8 and 12 weeks through various staining methods and immunohistochemistry.

The mean vascular density (MVD) of CS/nHA, CaP/nHA, and SA/nHA groups was (134.92±35.30) n/mm², (159.09±22.14) n/mm², (160.31±42.23) n/mm² at 12 weeks, respectively. The MVD of the CaP/nHA and SA/nHA groups were significantly higher than that of the CS/nHA group. The collagen volume fractions (CVF) were 34.13%, 51.53%, and 54.96% in the CS/nHA, CaP/nHA, and SA/nHA groups, respectively. In addition, the positive expression area ratios of OPN and CD31 in the CaP/nHA and SA/nHA groups were also significantly higher than those in the CS/nHA group.

The ability of SA/nHA composite microspheres in osteogenesis and angiogenesis is clearly superior to that of the CS/nHA group and is comparable to that of CaP/nHA, which has superior osteogenesis ability, indicating that SA/nHA composite microspheres have greater application prospects in bone tissue engineering.