Bone induction and defect repair by true bone ceramics incorporated with rhBMP-2 and Sr

Objective: To study the bone induction and defect repair of true bone ceramics (TBC) combined with rhBMP-2 and Sr. Methods: MC3T3-E1 cells were used to evaluate the bioactivity of the composite. Cell proliferation activity was detected by CCK-8, ALP activity was detected by p-nitrophenyl phosphate (PNPP), and the differences of material surface topography were observed by scanning electron microscopy (SEM). Bone induction was verified by the implantation in nude mice. The rabbit femoral condyle defect model was achieved to verify the bone defect repair ability of the material. Results: SEM results showed nearly the same surface morphology and cell proliferation quantified by CCK-8 showed that compared with TBC, both TBC&Sr and TBC&BMP-2&Sr had a significant promoting effect (P < 0.05). ALP activity result showed that the ALP activity of TBC&BMP-2&Sr was significantly higher than that of TBC alone (P < 0.05). The bone induction result showed that TBC&Sr had a small amount of new bone formation, and the new bone area was only 2.5 ± 0.11%. The bone induction activity of TBC&BMP-2&Sr was the highest, the new bone area was up to 75.36 ± 4.21%. Histological result of bone defect repair showed that TBC&BMP-2&Sr was also the highest, the new bone area was up to 72.42 ± 3.14%. The repair effect of TBC& BMP-2 was second, and better than that of TBC&Sr. Conclusion: TBC combined with rhBMP-2 and Sr had the good bioactivity, obvious bone conduction and bone defect repair performance, laying the foundation of clinical application potentially.

Osteoinduction in Novel Micropores of Partially Dissolved and Precipitated Hydroxyapatite Block in Scalp of Young Rats

Osteoinduction in muscles by porous ceramics has been reported to be a real phenomenon. In this study, osteoinduction in connective tissues was found in highly porous hydroxyapatite (HAp) ceramics with large specific surface areas. We have developed the combination method of the partial dissolution-precipitation (PDP) technique involving the stirring-supersonic treatment in 1.7 × 10−2 N HNO3 solution containing Ca2+ and PO43− to improve the surface and the bulk of commercially available synthetic HAp block (82.5% in porosity, 50–300 µm in pore size). The modified HAp was named as a partially dissolved and precipitated HAp (PDP-HAp). The PDP-HAp exhibited the porosities of 85–90%, the macropore sizes of 50–200 µm, and the specific surface areas of 1.0–2.0 m2/g, with microcracks. The aim of this study was to observe bone induction by the PDP-HAp with or without BMP-2 in scalp tissues of four-week-old rats. Young rats were divided into the PDP-HAp alone group and the PDP-HAp/BMP-2 group for a long-term observation. In the PDP-HAp group, bone induction occurred inside the many pores at nine months, and the ratio of induced bone was 12.0%. In the PDP-HAp/BMP-2 group, bone induction occurred in almost all pores at three months, and compact bone was found at nine months. The ratios of induced bone were 77.0% at three months and 86.0% at nine months. We believe that osteoinduction by the PDP-HAp might be different from the process of BMP-loaded HAp-induced bone formation, because the PDP-HAp has osteogenic microporous compartments with partially absorbable HAp crystals. The PDP technique may contribute to create bioceramics with osteoinductive property for bone regenerative medicine.

Effects of High-Concentration Alkali Treatment on Surface Bioactivity of Porous Titanium

Various surface treatment methods have been used to modify the surface activation of dense titanium. In this study, a high concentration of sodium hydroxide solution was used to treat porous titanium prepared by adding porous agent at different times. The results of the study showed that after alkali treatment, porous titanium was implanted into the back muscle of the dog and the implanted sample was taken out for bone formation protein-2 enzymatic immunoassay after 6 months. The porous titanium inner wall has been covered. The microstructures vary with the treatment time. The treated surface can induce the formation of hydroxyapatite deposition and promote the expression of BMP-2, which shows good bone induction. High concentration alkali treatment of porous titanium, the method is simple, can shorten the HA formation time, can effectively activate porous titanium inner and outer surfaces, is an effective method to prepare bioactive porous titanium.