APATITES FORMATION ON ELECTRODEPOSITED CALCIUM PHOSPHATES IN THE Ca(NO3)2 / NH4H2PO4 AND CаCOз / Ca(H2PO4)2 SYSTEMS

Методом электрохимического осаждения на титановых пластинах при комнатной температуре в двухэлектродной ячейке при постоянной плотности тока 30 мА/см и времени осаждения 10 мин получены кальцийфосфатные покрытия: брушитные в системе Ca (NO )/ NH H PO при pH = 4 и композитные (брушит/кальцит/апатит) в системе CaCOjCa (HPO ) при pH = 5. Выдерживанием кальцийфосфатных покрытий обоих типов в модельном растворе SBF в течение 1 месяца определяли апатитообразующую способность (биоактивность). Новообразованный аморфизированный апатитовый слой после термообработки при 800°С кристаллизовался в Д -трикальцийфосфат/гидроксиапатит на брушитных покрытиях и в гидроксиапатит на композитных покрытиях за счет присутствия кальцита, карбонат-ионы которого являются инициаторами образования гидроксиапатита, а также апатитных наночастиц в исходном покрытии. Полученные кальцийфосфатные покрытия перспективны в качестве биопокрытий повышающих остеоинтеграцию металлических имплантатов. Calcium phosphate coatings on titanium plates were obtained by electrochemical deposition at room temperature in a two-electrode cell at a constant current density of 30 mA/sm and a deposition time of 10 min, and brushite coatings from Ca (NO )/NHHPO system at pH = 4, and composite (brushite/calcite/apatite) coatings from the CaCO/ Ca(HPO) system at pH = 5. The apatite-forming ability (bioactivity) was determined by soaking both types of calcium phosphate coatings in a model SBF solution during month. The newly formed amorphized apatite layer after heat treatment at 800 °С crystallized into p -tricalcium phosphate/hydroxyapatite on brushite coatings and hydroxyapatite on composite coatings due to the presence of calcite, whose carbonate ions initiate formation of hydroxyapatite, as well as apatite nanoparticles in the initial coating. The obtained calcium phosphate coatings are promising as biocoatings capable to increase osseointegration of metal implants.

Effect of power of ultrasound during micro-arc oxidation on morphology, elemental and phase composition of calcium phosphate coatings

The effect of the magnitude of the US (ultrasound) power applied during the MAO (micro arc oxidation) process on the morphology, elemental and phase composition of the CaP coatings was studied. The US at different power (50-200 W) applying during the MAO process led to the local destruction of the structure elements (spheres and pores) and local filling the pore spaces on the coating surface, and to the formation of local macro-pores inside the coatings near the substrate. Such morphological transformations led to the surface and structure heterogeneity of the coatings, increasing of the surface roughness from 3.0 to 4.5 μm and of the thickness from 50 to 60 μm. The US application at different power did not affect significantly the elemental composition of the coatings. At the same time, under applied US with power more than 100 W, the state of the coatings transformed from X-ray amorphous to the quasiamorphous with the small incorporation of crystalline phases of CaHPO4 and β-Ca2P2O7.

Effect of ultraviolet irradiation or diffuse discharge plasma on structure and surface electrical charge of micro-arc calcium phosphate coatings

The studies of the effect of ultraviolet (UV) irradiation and plasma of a runaway electron preionized diffuse discharge (REP DD) post-treatments on the surface structure and electrical charge of the micro-arc oxidation (MAO) coatings were performed. The UV irradiation and plasma treatment did not effect on the morphology, roughness and thickness of the MAO coatings. However, these post-treatments led to formation of the small fraction of the crystalline CaHPO4phase in the X-ray amorphous structure of the coatings. Moreover, the UV and REP DD plasma treatments increased the electrostatic potential (EP) negative values from –85 mV to –126 mV of the coatings in the following order: MAO < MAO/UV (for 5 min) < MAO/Plasma (with 10,000 pulses) < MAO/UV (for 20 min) < MAO/Plasma (with 80,000 pulses).

Improving the in vitro Degradation, Mechanical and Biological Properties of AZ91-3Ca Mg Alloy via Hydrothermal Calcium Phosphate Coatings

For many years, calcium phosphate coatings to tailor the degradation behavior of magnesium and magnesium-based alloys for orthopaedic applications have received lots of research attention. However, prolong degradation behavior, its effect on biological and mechanical properties as well as osteoblastic response to single-step hydrothermally deposited calcium phosphate coatings remain poorly documented. In this study, Alamar blue assay, cell attachment, live/dead assay, and qRT-PCR were done to study the biological response of the coatings. Furthermore, immersion testing in SBF for 28 days and compression testing of the degraded samples were carried out to examine the degradation behavior and its effect on mechanical properties. The results indicated that coatings have a significant influence on both the substrate performance and structural integrity of coated AZ91-3Ca alloy. Immersion test revealed that coating deposited at pH 7, 100°C (CP7100) improves the hydrogen evolution rate by 65% and the degradation rate by 60%. As the degradation performance of coated samples improves so does the mechanical strength. CP7100 samples successfully retained 90% of their compressive strength after 14 days of immersion while bare AZ91-3Ca alloy lost its mechanical integrity. Furthermore, biological studies show that cells are happily proliferating, differentiating, and adhering to the coating surfaces, which indicates, improved osteointegration and osteogenesis with no sign of alkaline poisoning. qRT-PCR results showed that calcium phosphate coatings enhanced the mRNA levels for RUNX2, Col1A, and ALP that may exhibit a speedy bone recovery. Thus, calcium phosphate coatings produced via a single-step hydrothermal method improve the degradation behavior, mechanical integrity and stimulate the differentiation of osteoblast lining. This leads toward faster bone regeneration, which shows a great potential of these coatings to be used on degradable implants as a bioactive protective layer.