Moscow State University of Medicine and Dentistry named after A.I. Evdokimov

Relevance. The effect of a tissue engineering construct based on synthetic octacalcium phosphate activated with plasmid DNA with vascular endothelial growth factor gene on bone morphogenesis at the jaw defect sites of patients was studied. It is shown that the studied osteoplastic material stimulates osteosynthesis pathways already at early stages, and xenogenic hydroxyapatite, triggers osteogenesis processes with considerable delay and does not have time to form a full-fledged bone structure by 6 months.Aim. Evaluate the dynamics of reparative osteogenesis based on the results of histomorphometric diagnostics in patients with defects in the jaw bones of various configurations and lengths with an implanted bone matrix based on synthetic octacalcium phosphate activated with plasmid deoxyribonucleic acid with genes of vascular endothelial growth factor.Materials and methods. Histomorphological examination of bone tissue biopsy of jaws was carried out in 50 patients of both genders, who needed additional volume of bone tissue to install dental implantation. Patients were divided into 2 groups by type of grafted material. 6 months after the surgery, bone biopsies were taken from the bone sites at the stage of implant placement. Histomorphological patterns and histomycrophotograms were studied in bone biopcies.Results. In bone tissue biopsies of patients implanted with a tissue engineering construct based on synthetic octacalcium phosphate activated with plasmid DNA with vascular endothelial growth factor gene, it was revealed that after 6 months there was prevaluation of mature bone tissue (42,71%), with the proportion of differentiated plate bone tissue being < 90%.Conclusions. Histomorphometric analysis showed that in patients implanted with a tissue engineering construct based on synthetic octacalcium phosphate activated with plasmid DNA with vascular endothelial growth factor gene, after 6 months, early rearrangement of bone tissue into a mechanically dense and highly mineralized structure was detected.

Transformation from calcium sulfate to calcium phosphate in biological environment

The formation of a nano-apatite surface layer is frequently considered a measure of bioactivity, especially for non-phosphate bioceramics. In the present study, strontium-doped calcium sulfate, (Ca,Sr)SO4, was used to verify the feasibility of this measure. The (Ca,Sr)SO4 specimen was prepared by mixing 10% SrSO4 by weight with 90% CaSO4·½H2O powder by weight. A solid solution of (Ca,7.6%Sr)SO4 was then produced by heating the powder mixture at 1100 °C for 1 h. The resulting (Ca,Sr)SO4 specimen was readily degradable in phosphate solution. A newly formed surface layer in the form of flakes was formed within one day of specimen immersion in phosphate solution. Structural and microstructure–compositional analyses indicated that the flakes were composed of octacalcium phosphate (OCP) crystals. An amorphous interface containing OCP nanocrystals was found between the newly formed surface layer and the remaining (Ca,Sr)SO4 specimen. The specimen was also implanted into a rat distal femur bone defect. In addition to new bone, fibrous tissue and inflammatory cells were found to interlace the (Ca,Sr)SO4 specimen. The present study indicated that a more comprehensive evaluation is needed to assess the bioactivity of non-phosphate bioceramics.

Silica/OCP Affects the Viability of Osteoblasts through ROS-Induced Autophagy

Objective. To explore the effects of silicone gel nanoparticles modified with octacalcium phosphate on the surface (silica/OCP) polymer drugs on the proliferation of osteoblasts and autophagy. Method. Silica/OCP was prepared in vitro, and the quality of the sample preparation was tested through characterization experiments. The osteoblast cell line (hFOB1.19) was treated with silica/OCP, autophagy inhibitor (3-methyladenine (3-MA)), and silica/OCP+3-MA, respectively. The proliferation of hFOB1.19 cells was detected through the methylthiazolyldiphenyl-tetrazolium bromide (MTT) kit. Flow cytometry was used to detect the cell apoptosis. The change in protein beclin1 and P62 expression in hFOB1.19 cells was observed in Western blot. An ROS detection kit was used to detect the content of reactive oxygen species in hFOB1.19 cells. Results. Silica/OCP was a sphere with a particle size of 50 nm to 130 nm and had an OCP phase in electron projection microscopy and X-ray diffraction techniques. The results indicated that OCP successfully modified silica and the material was successfully prepared. An MTT kit and flow cytometry test showed that the cell viability of the cells treated with silica/OCP increased significantly ( P < 0.05 ), and the intracellular apoptosis phenomenon was significantly decreased ( P < 0.05 ) compared to the control group. Moreover, the inhibition of cell viability and promotion of apoptosis caused by the autophagy inhibitor 3-MA can be rescued. Western blotting demonstrated that the protein level of beclin1 in osteoblasts reached the highest after six hours of treatment with silica/OCP, and the protein level of p62, the substrate protein of autophagy, reached the lowest. At the same time, treatment of cells with the autophagy inhibitor 3-MA and silica/OCP+3-MA found that the protein levels of beclin1 and p62 in the silica/OCP+3-MA group were adjusted back compared to the 3-MA group. After adding the autophagy inhibitor, the reactive oxygen content in the cell was significantly increased ( P < 0.05 ) in the silica/OCP group. In the presence of intracellular reactive oxygen inhibitors catalase and silica/OCP, the cell viability of osteoblasts was significantly lower than that of the silica/OCP group but significantly higher than that of the silica/OCP+3-MA group. The apoptosis level of the silica/OCP+catalase group was also significantly lower than that of the silica/OCP+3-MA group ( P < 0.05 ) but was significantly higher than that of the silica/OCP group ( P < 0.05 ). Conclusion. Silica/OCP nanoparticles can upregulate the level of autophagy in osteoblasts and promote the proliferation of osteoblasts.

Octacalcium Phosphate for Bone Tissue Engineering: Synthesis, Modification, and In Vitro Biocompatibility Assessment

Octacalcium phosphate (OCP, Ca8H2(PO4)6·5H2O) is known to be a possible precursor of biological hydroxyapatite formation of organic bone tissue. OCP has higher biocompatibility and osseointegration rate compared to other calcium phosphates. In this work, the synthesis of low-temperature calcium phosphate compounds and substituted forms of those at physiological temperatures is shown. Strontium is used to improve bioactive properties of the material. Strontium was inserted into the OCP structure by ionic substitution in solutions. The processes of phase formation of low-temperature OCP with theoretical substitution of strontium for calcium up to 50 at.% in conditions close to physiological, i.e., temperature 35–37 °C and normal pressure, were described. The effect of strontium substitution range on changes in the crystal lattice of materials, the microstructural features, surface morphology and biological properties in vitro has been established. The results of the study indicate the effectiveness of using strontium in OCP for improving biocompatibility of OCP based composite materials intended for bone repair.

A CRYSTAL CHEMISTRY OF HYDROXYAPATITE : A REVIEW

In chemistry of inorganic crystals, the octacalcium phosphate (OCP) is an apatite based crystals and having a hydrated layers which used in producing of needle or plate-shaped hydroxyapatite (HAP) nanocrystals. Although, the crystals is prepared by a dissolution precipitation reaction. These reaction led to a hexagonal HAP nanocrystals formation under hydrothermal condition from OCP at 180 for 3 hours with pH of solution adjusted to 5.5 and incorporating dicarboxylate e.g. succinate (OOC.(CH2)2.COO)2- ions having Ca/P molar ratio is expected to be 1.56±0.02, where the morphology of OCP are retained. During incorporating of succinate ions in OCP crystals, the hydrogen phosphate (HPO42-) ions in the hydrated layers of OCP are being substituted by succinate ions. Since the crystal system of HAP is hexagonal and its crystalline size in the longitudinal direction of various (a,b,c) axes depending on the thickness of the laminated plate-shaped HAP crystals. Here, their size as perpendicular to the (100) plane which is calculated by introducing of Scherrers equation, D100 = Kλ/(β cos ). The organically modified OCP which generated to HAP have unique nanostructure with micrometer thickness are characterized by using of SEM, FTIR and X-ray diffraction analysis.