Osteoinductivity of Porous Biphasic Calcium Phosphate Ceramic Spheres with Nanocrystalline and Their Efficacy in Guiding Bone Regeneration

Abstract

Conventional biphasic calcium phosphate (BCP) bioceramics are facing many challenges to meet the demands of regenerative medicine, and their biological properties are limited to a large extent due to the large grain size in comparison with nanocrystalline of natural bone mineral. Herein, this study aimed to fabricate porous BCP ceramic spheres with nanocrystalline (BCP-N) by combining alginate gelatinizing with microwave hybrid sintering methods and investigated their in vitro and in vivo combinational osteogenesis potential. For comparison, spherical BCP granules with microcrystalline (BCP-G) and commercially irregular BCP granules (BAM, BCP-I) were selected as control. The obtained BCP-N with specific nanotopography could well initiate and regulate in vitro biological response, such as degradation, protein adsorption, bone-like apatite formation, cell behaviors, and osteogenic differentiation. In vivo canine intramuscular implantation and rabbit mandible critical-sized bone defect repair further confirmed that nanotopography in BCP-N might be responsible for the stronger osteoinductivity and bone regenerative ability than BCP-G and BCP-I. Collectedly, due to nanotopographic similarities with nature bone apatite, BCP-N has excellent efficacy in guiding bone regeneration and holds great potential to become a potential alternative to standard bone grafts in bone defect filling applications.

Enhancing mechanical and biological properties of biphasic calcium phosphate ceramics by adding calcium oxide

“…11,28,35 Our previous studies have certified that compared to the conventional ones with micro-scale surface structure, BCP ceramics with nanocrystalline can promote osteogenic differentiation of BMSCs in vitro, and improve osteoinductivity and bone regeneration in vivo. 7 In the present study, SEM images (Figure 1) showed that CaO addition could markedly inhibit the grain growth in BCP ceramics, as the grain size of BCP ceramics gradually decreased with the increase of CaO amount from 1% to 4%. When the content of CaO increased up to 3%, the average grain sizes of the obtained BCP ceramics (<270 nm) F I G U R E 7 The expression of osteogenic genes (ie Runx-2, Osx, Alp, Ocn, and Opn) in BMSCs cultured on the four kinds of BCP ceramics.…”

“…Cell proliferation was quantified by AlamarBlue method as mentioned before. 7 BMSCs attached on the samples were also stained with TRITC-conjugated-phalloidin (1:200, Sigma) for cytoskeletal protein (F-actin), and DAPI (1:200, Sigma) for cell nuclei, and then the staining was examined under a confocal laser scanning microscopy (CLSM, TCS SP5, Leica, Germany). The morphology of BMSCs was also observed by SEM following the procedures as described before.…”

“…The quantitative ALP activity was tested colorimetrically using Alkaline Phosphatase Assay Kit (Beyotime, China) as previous described. 7,20 To investigate the mineralization of the BMSCs on the obtained samples, Alizarin Red S (Alfa Aesar, USA) were conducted according to the manufacturer's procedures, and the staining was also semi-quantified using ImageJ software. Moreover, after 7 days of culture, BMSCs cultured on the samples were…”

“…28 Our previous studies employed microwave sintering method to fabricate BCP ceramics with nanocrystalline, suggesting that the nanostructure characteristics endow them with excellent biological properties in comparison with the conventional ones. 7,11 However, these BCP nanoceramics did not fully display the advantages of nanoceramics in superior mechanical strength, partly due to the relatively low density caused by the small shrinkage in the sintering process. Therefore, it is urgent to develop an effective strategy to enhance the mechanical properties and biological performances of BCP ceramics simultaneously.…”

Recent advance in surface modification for regulating cell adhesion and behaviors

“…Hydroxyapatite, tricalcium phosphate, amorphous calcium phosphate, and biphasic calcium phosphate have inorganic composition and crystal structure similar to those of natural bones, so they are the most commonly used bioceramics in orthopedic surgery. In recent years, with the research and development of tissue engineering, porous CPCs, as a kind of bone tissue engineering cell scaffolds, have been widely used in the repair and replacement of bone defects [112]. At present, many methods of preparing porous ceramics have been developed, such as organic foam impregnation method, foaming method, and adding pore-forming agent ( Figure 15).…”