Biphasic Calcium Phosphate/Chitosan/Polyacrylonitrile/Polylactic Acid-Glycolic Acid (PLGA) Nanocomposite Stent for Repair and Osteogenesis of Oral Alveolar Bone Defect

Abstract

ABSTRACTThe ability of sol-gel micro-nano biphasic calcium stent to repair oral alveolar bone defects was investigated in this study, and its osteogenesis performance was also analyzed. Biphasic calcium phosphate (BCP) was synthesized by wet method, which was combined with chitosan (CS), polyacrylonitrile (PAN), and polylactic acid-glycolic acid (PLGA). Then, the BCP/CS/PAN/PLGA nanocomposite stent was prepared by vacuum freeze-drying technology. The micro-nano composite stent was combined with the bone morphogenetic protein-2 (BMP-2) gene, so as to obtain the sol-gel micro-nano biphasic calcium BMP-2/BCP/CS/PAN/PLGA composite stent. Besides, the composite stent should be measured in terms of compressive strength, porosity, structure, and morphological features. The healthy female rhesus monkeys were taken as the research animals, and the iliac bone marrow was extracted by puncture. The mesenchymal stem cells (MSCs) were obtained by density gradient centrifugation, and their osteogenic differentiation ability was observed. The MSCs were culturedin vitrowith BMP-2/BCP/CS/PAN/PLGA composite stent, methylthiazolyldiphenyl-tetrazolium bromide (MTT) was applied to detect cell adhesion and proliferation, and the alkaline phosphatase (ALP) activity was employed to analyze its osteogenic properties on stent materials. In addition, the expression of BMP-2 was detected by Western blot. The alveolar bone defect models were established and divided into group A (MSCs + BMP-2/BCP/CS/PAN/PLGA), group B (BMP-2/BCP/CS/PAN/PLGA), group C (BCP/CS/PAN/PLG), and group D (control group, reposition of gingival flap and suture) according to different implant materials. The changes of bone defect area in different groups were detected by gross examinations and X-ray, so that the new bone density was analyzed. The results showed that the BCP/CS/PAN/PLGA composite stent exhibited a porous structure combining multiple pores/small pores, with an average pore diameter (PD) of 400–500µm, maximum compressive strength of 6.02 Mpa, and porosity of 86.82%. MSCs differentiated into osteoblasts under osteogenic induction conditioned medium, and the optical density (OD) of CS + MSCs/BMP-2/BCP/CS/PAN/PLGA cells was greater in contrast to that of MSCs/BMP-2/BCP/CS/PAN/PLGA cells on the 1st and 7th day of culture, showing a statistical difference(P< 0.05). The gross examination and X-ray of bone defect area in group A showed that its bone structure and density were very close to those of normal bone (all materials were absorbed, and newly formed bone cells were active); the CT value of alveolar bone in groups A, B, C, and D was 1,092.45± 15.87 g/cm3, 932.26± 16.75 g/cm3, 859.51 ±17.86 g/cm3, and 787.96± 16.54 g/cm3, respectively. There was no marked difference in CT values between group A and normal alveolar bone (P> 0.05), while the CT value of alveolar bone in group A was higher obviously than the value of groups C and D(P< 0.05). It indicated that the composite stent based on sol–gel micro-nano biphasic calcium BMP-2/BCP/CS/PAN/PLGA could promote the repair of oral alveolar bone defect and its osteogenesis, thereby providing a reference for the oral clinical treatment of periodontal bone defects.