HA Crystals Research Articles

High-aspect-ratio nanostructured hydroxyapatite: towards new functionalities for a classical material.

Hydroxyapatite-based materials have been widely used in countless applications, such as bone regeneration, catalysis, air and water purification or protein separation. Recently, much interest has been given to controlling the aspect ratio of hydroxyapatite crystals from bulk samples. The ability to exert control over the aspect ratio may revolutionize the applications of these materials towards new functional materials. Controlling the shape, size and orientation of HA crystals allows obtaining high aspect ratio structures, improving several key properties of HA materials such as molecule adsorption, ion exchange, catalytic reactions, and even overcoming the well-known brittleness of ceramic materials. Regulating the morphogenesis of HA crystals to form elongated oriented fibres has led to flexible inorganic synthetic sponges, aerogels, membranes, papers, among others, with applications in sustainability, energy and catalysis, and especially in the biomedical field.

Initial solution pH value for the construction of a 3D hydroxyapatite via the trisodium citrate-assisted hydrothermal route.

In this study, a trisodium citrate (TSC)-assisted hydrothermal method is utilized to prepare three-dimensional hydroxyapatite (3D HA). Understanding the role of TSC in the preparation of 3D HA crystals may provide valuable methods to design advanced biomaterials. As one of the indexes of solution supersaturation, the initial pH (ipH) value can not only directly affect the nucleation rate, but also affect the growth of HA crystals. In this work, the effect of the ipH on the microstructure, particle size distribution, and specific surface area of the 3D HA is explored. Results showed that the morphology of 3D HA transformed from a bundle to a dumbbell ball and then a dumbbell with an increase in the ipH. A corresponding mechanism of such a structural evolution was proposed, providing inspiration for the fabrication of innovative 3D HA structures with enhanced biological functionality and performance.

Cathodic electrophoretic deposited HA-rGO-ZnO ternary composite coatings on ZK60 magnesium alloy for enhanced corrosion stability

HA-rGO-ZnO ternary composite coatings were successfully prepared on ZK60 magnesium alloy using cathodic electrophoretic deposition method. XRD analysis proved the addition of ZnO nanoparticles induced a significantly reduced crystallinity in hydroxyapatite and the tensile strain values of HA-rGO-ZnO composite coatings gradually decreased as the content of ZnO increased. SEM analyses revealed that the HA and ZnO nanoparticles were anchored on rGO nanosheets and a closely-packed network of recrystallization needle-like ZnO and mineralization HA crystals was formed on the surface of HA-rGO-ZnO coated sample. The resulting composite coating exhibited a uniform and compact HA-rGO-16ZnO composite coating, with well adhered to the ZK60 magnesium alloy substrate. The HA-rGO-16ZnO coated sample exhibited the highest corrosion resistance with lowest icorr (1.12 × 10−6 A/cm2) and the highest Ecorr (−1.43 V/SCE) value when compared to HA-rGO-14ZnO and HA-rGO-18ZnO samples after immersion in a SBF for 10 min. Compared to HA-rGO-ZnO coated samples after 10 min of immersion in SBF, HA-rGO-ZnO coated samples after 3 days of immersion in SBF exhibited a remarkably improved corrosion resistance and rapid inducing of the apatite layer precipitated on the surface of the composite coatings. The microstructure and composition for the coated samples after 3 days of immersion in SBF also confirm that the presence of a apatite layer on the composite coatings. HA-rGO-18ZnO coated samples after 3 days of immersion in SBF showed the lowest icorr value, which indicating HA-rGO-18ZnO ternary composite coatings dramatically improved the formation ability of the apatite layer and led to an enhancement in the bioactivity. Accordingly, it is believed that the HA-rGO composite coating incorporated with ZnO will be a potential candidate for bone biomedical applications.

Rapid biomimetic mineralization of keratin scaffold via electrodeposition with potential for bone regeneration

For bone regeneration, rapid mineralization is of particular importance in the preparation of biomimetic bone scaffolds, as for avoiding the drawbacks of prolonged mineralization which will cause the loss of growth factors and degradation. In this research, we developed a relatively rapid mineralization approach for constructing biomimetic keratin scaffold that exhibited highly interconnected pore and natural bone mimetic calcium phosphate coating by applying an electrodeposition technique. Mineralized keratin scaffold was obtained by freeze drying followed by electrodeposition for rapid biomimetic mineralization. The mineral coating morphology, component and crystal structure could be controllably tailored by manipulating the deposition electrode, voltage and duration. A satisfying coating of apatite layer on keratin scaffold could be obtained within a couple of hours by electrodeposition. By increasing the voltage and duration, a more favored amount of apatite coating which dominated by HA crystal could be formed. In addition, cell regeneration assay showed that mineralized biomimetic keratin scaffold exhibited more suitable supporting platform for the proliferation and osteoblastic differentiation of MC3T3 cell over pure keratin scaffold. Thus, the rapid electrodeposition mineralization approach presented in this work could be highly desired for fabricating biomimetic scaffolds in which biological molecules were loaded for functional bone tissue engineering applications.

The study of hydroxyapatite growth kinetics on CP – Ti and Ti65Zr treated by Plasma electrolytic oxidation process

The kinetics of hydroxyapatite growth on titanium alloys (CP–Ti and Ti65Zr) was studied. Specimens were treated by Plasma Electrolytic Oxidation (PEO) and immersed into the Hanks' solution. The PEO method was performed at AC mode with the current density of 4 A/dm2 in an electrolyte containing calcium acetate and calcium glycerophosphate, allowing the inclusion of calcium and phosphorus in the obtained oxide layer, which promotes the osseointegration when applied to bone tissue. The treated specimens were immersed in the Hanks’ solution with different exposure times, followed by studying changes in morphology, chemical, and phase composition. In addition, the surface wettability was tested, and the corrosion behavior of the treated samples was investigated. Tiny HA crystals can be seen on the surface of CP-Ti samples treated by PEO for 5 and 30 min. The morphology with a distinct layer of HA was obtained for the Ti65Zr sample after 5 min of PEO treatment. As for the immersion times, the highest crystal growth velocity was observed for the Ti65Zr of 5 min of PEO and 14 days of immersion. The change in morphology and EIS analysis confirms the observed behavior. Finally, based on the XRD analysis for the Ti65Zr of 5 min PEO treatment samples, the Srilankite phase in an amount of 60% is responsible for the crystal growth, resulting in the best crystal growth velocity and good corrosion properties (Rp = 0.732 MΩ cm2).

Protocol for Cell Colonization and Comprehensive Monitoring of Osteogenic Differentiation in 3D Scaffolds Using Biochemical Assays and Multiphoton Imaging.

The goal of bone tissue engineering is to build artificial bone tissue with properties that closely resemble human bone and thereby support the optimal integration of the constructs (biografts) into the body. The development of tissues in 3D scaffolds includes several complex steps that need to be optimized and monitored. In particular, cell-material interaction during seeding, cell proliferation and cell differentiation within the scaffold pores play a key role. In this work, we seeded two types of 3D-printed scaffolds with pre-osteoblastic MC3T3-E1 cells, proliferated and differentiated the cells, before testing and adapting different assays and imaging methods to monitor these processes. Alpha-TCP/HA (α-TCP with low calcium hydroxyapatite) and baghdadite (Ca3ZrSi2O9) scaffolds were used, which had comparable porosity (~50%) and pore sizes (~300-400 µm). Cell adhesion to both scaffolds showed ~95% seeding efficiency. Cell proliferation tests provided characteristic progression curves over time and increased values for α-TCP/HA. Transmitted light imaging displayed a homogeneous population of scaffold pores and allowed us to track their opening state for the supply of the inner scaffold regions by diffusion. Fluorescence labeling enabled us to image the arrangement and morphology of the cells within the pores. During three weeks of osteogenesis, ALP activity increased sharply in both scaffolds, but was again markedly increased in α-TCP/HA scaffolds. Multiphoton SHG and autofluorescence imaging were used to investigate the distribution, morphology, and arrangement of cells; collagen-I fiber networks; and hydroxyapatite crystals. The collagen-I networks became denser and more structured during osteogenic differentiation and appeared comparable in both scaffolds. However, imaging of the HA crystals showed a different morphology between the two scaffolds and appeared to arrange in the α-TCP/HA scaffolds along collagen-I fibers. ALP activity and SHG imaging indicated a pronounced osteo-inductive effect of baghdadite. This study describes a series of methods, in particular multiphoton imaging and complementary biochemical assays, to validly measure and track the development of bone tissue in 3D scaffolds. The results contribute to the understanding of cell colonization, growth, and differentiation, emphasizing the importance of optimal media supply of the inner scaffold regions.

Alginate Coating Charged by Hydroxyapatite Complexes with Lactoferrin and Quercetin Enhances the Pork Meat Shelf Life.

In this work, the effect of an alginate-based coating loaded with hydroxyapatite/lactoferrin/quercetin (HA/LACTO-QUE) complexes during the storage of pork meat was evaluated. FT-IR spectra of HA/LACTO-QUE complexes confirmed the adsorption of QUE and LACTO into HA crystals showing the characteristic peaks of both active compounds. The kinetic releases of QUE and LACTO from coatings in an aqueous medium pointed out a faster release of LACTO than QUE. The activated alginate-based coating showed a high capability to slow down the growth of total viable bacterial count, psychotropic bacteria count, Pseudomonas spp. and Enterobacteriaceae during 15 days at 4 °C, as well as the production of the total volatile basic nitrogen. Positive effects were found for maintaining the hardness and water-holding capacity of pork meat samples coated with the activated edible coatings. Sensory evaluation results demonstrated that the active alginate-based coating was effective to preserve the colour and odour of fresh pork meat with overall acceptability up to the end of storage time.

Comparative structural refinement of nanocrystalline hydroxyapatite

An attempt was made to make a comparative structural refinement of nanocrystalline HA between the mechano-synthesis (MS), ultrasonic-assisted precipitation (UP), biogenic-based process (BP), and commercial grade (CG). Rietveld refinement of XRD patterns illustrated the main characteristic peaks of hexagonal HA. The anisotropic crystallite sizes were observed, where the smallest crystallite sizes of D〈001〉 (24.5 ± 3.1 nm) and D〈100〉 (17.7 ± 1.1 nm) were recorded in the 7h MS specimen. On the contrary, the highest D〈001〉/D〈100〉 ratio of 7.68 was achieved for the UP HA, showing HA crystals preferentially grew in the c-axis direction. The narrow particle size distribution of the 7h MS specimen, with an average diameter of 9 ± 2 nm, was smaller than the crystallite size estimated from the refined XRD pattern, indicating the single-crystal feature. Overall, MS HA holds great promise as an effective medical strategy for treating bone cavities.

Evaluation of corrosion resistance, mechanical integrity loss and biocompatibility of PCL/HA/TiO2 hybrid coated biodegradable ZM21 Mg alloy

A novel PCL/HA/TiO 2 hybrid coating on ZM21 Mg alloy substrate has been investigated for corrosion resistance, biocompatibility and mechanical integrity loss in terms of bending, compressive and tensile strength in physiological media. The prepared hybrid coating was dip coated over ZM21 from HA/TiO 2 and PCL solutions followed by creating a microporous PCL layer by utilizing Non-solvent Induced Phase Separation (NIPS) technique. The electrochemical measurement and in-vitro degradation study in SBF after 28 days showed that the PCL/HA/TiO 2 hybrid coating reduced H2 evolution rate, weight loss, and corrosion rate by 64, 116 and 118 times respectively, as compared to uncoated ZM21 samples. The surface studies carried out using SEM-EDX, FTIR and XRD revealed formation of highly stable 3d flower-like HA crystals with Ca/P ratio of 1.60 in the PCL micropores. This dense apatite growth effectively protected the PCL/HA/TiO 2 hybrid coated samples to maintain the good mechanical integrity even after 28 days of immersion as compared to HA/TiO 2 composite coated, As-polished (A/P) and As-machined (A/M) samples. The failure analysis of samples under mechanical loading were performed using SEM-BSE-EBSD. The in-vitro cellular viability of L929 fibroblast cells on PCL/HA/TiO 2 hybrid coating was found 50.47% higher with respect to control group, whereas bacterial viability was supressed by 57.15 and 62.35% against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacterial models. The comprehensive assessment indicates PCL/HA/TiO 2 hybrid coating as a suitable candidate to delay early degradation and mechanical integrity loss of Mg-based alloys for devising biodegradable orthopaedic implant.

In vitro evaluation of degradation, cytocompatibility and antibacterial property of polycaprolactone/hydroxyapatite composite coating on bioresorbable magnesium alloy

Polycaprolactone/hydroxyapatite (PCL/HA) composite coating was fabricated by a combination of hydrothermal and dipping methods to delay the degradation of Mg alloy AZ31 as bioresorbable materials. The PCL/HA coating was composed of nano rod-shape HA crystals and PCL filled in the space of HA crystals. Compared with the single HA coating, the binding strength between the PCL/HA composite coating and Mg alloy was obviously improved and the PCL/HA coating still adhered to the surface of AZ31 substrate even after 38 days of immersion. The electrochemical corrosion rate of HA coated sample was reduced by ten times after being filled by PCL. The electrochemical impedance spectroscopy (EIS) and immersion test results showed that the PCL/HA composite coating could provide a more effective barrier for Mg substrate than the HA coating alone. The cytocompatibility and the antibacterial property of HA coating and PCL/HA coating were evaluated by culturing with bone marrow-derived mesenchymal stem cells (BMSCs) and methicillin-resistant staphylococcus aureus (MRSA) for 24 h under direct culture conditions, respectively. The PCL/HA composite coating showed better BMSC cell compatibility, more suitable for BMSC adhesion than HA coating alone and showed a potential application prospect as a biological materials. However, from the perspective of clinical applications, the antibacterial property of PCL/HA composite coating needs to be further improved.

Bone-like hydroxyapatite anchored on alginate microspheres for bone regeneration

Inspired by the initial mineralization process in bone matrix vesicles (MVs), we used Dulbecco's Modified Eagle's Medium (DMEM) to establish the similar physiological environment to that in MVs for biomimetic mineralization on alginate (ALG) microspheres. The results showed that HA crystals were firstly formed and anchored on the membrane of microspheres like the initial deposition of hydroxyapatite crystals inside MVs. With the continuous growth and accumulation of mineral crystals, HA coating was finally formed on ALG microspheres. The mineralized ALG microspheres (M-ALG microspheres) show good biocompatibility and osteogenic performance. The HA coating is also conducive to the active migration of osteoblasts to the surface of M-ALG microspheres. Collectively, bone-like HA crystals anchored on ALG microspheres may provide a good prospect to promote the repair of bone defects.

In Ukrainian

Microwave irradiation (MWI) in the synthesis of materials has been an actively developing branch of science for the last three decades. Structures based on calcium phosphates (CaP) are one of the most well-known and widely used synthetic biomaterials in orthopedics and dentistry. The main topic of this review is the use of MWI in the formation of biomaterials based on calcium phosphate phases and their complexes with biopolymers (chitosan, alginate, silk fibroin). The physical bases of MW interaction with different materials are considered, including the influence of this irradiation on the structure, physicochemical and mechanical properties of biomaterials (crystallite size, porosity, strength, capability to absorb and release drugs). The main heating mechanisms during MWI are described, namely: the dipolar losses, and losses of conductivity. Important advantages of MWI treatment are reducing processing time, reducing electricity use, reducing waste and improving quality of the synthesized biomaterials. A list and comparison is made of articles describing the production of HA crystals with different morphology (nanowires, spherical, needle- and rod-shaped) with all the initial conditions and their effect on the synthesized material. The latest developments in the field of biomaterials conducted based on the laboratory “Bionanocomposite” of Sumy State University are considered. The original synthesis method of CaP-biopolymer materials is described, as well as the advantages of the synthesized scaffolds over foreign developments. It is expected that this review of the interdisciplinary topic will contribute to the further study of other new applications of microwave technologies in the synthesis of the latest modern biomaterials created by scientists, biomedical engineers in other laboratories and institutions in Ukraine and around the world.

Ag–Sr doped mesoporous bioactive glass nanoparticles loaded chitosan/gelatin coating for orthopedic implants

AbstractIn this study, we investigated surface and biological properties of Ag–Sr‐doped mesoporous bioactive glass nanoparticle (Ag–Sr MBGN) loaded chitosan/gelatin coatings deposited by electrophoretic deposition (EPD) on 316L stainless steel. The EPD parameters, that is, deposition time, applied voltage, and distance between the electrodes was optimized by the Taguchi design of experiment (DoE) approach. Scanning electron microscopy (SEM) images illustrated the spherical morphology of the synthesized Ag–Sr MBGNs with the mean particle size of 160 ± 20 nm. Energy‐dispersive X‐ray (EDX) spectroscopy results confirmed the presence of Ag and Sr in the synthesized MBGNs. Optimum EPD parameters determined by DoE approach were 5 g/L of Ag–Sr MBGNs, deposition time of 5 min, and applied voltage of 30 V. SEM images confirmed that the coatings were fairly homogenous. Fourier‐transform infrared spectroscopy and EDX results confirmed the presence of chitosan, gelatin, and Ag–Sr MBGNs in the coatings. Chitosan/gelatin/Ag–Sr MBGN composite coatings exhibited suitable wettability for the protein attachment and proliferation of osteoblast cells. The composite coatings exhibited suitable adhesion strength with the substrate. The coatings developed HA crystals upon immersion in simulated body fluid. The results of the turbidity test confirmed that the coatings are antibacterial to the Escherichia coli cells.

Rapid structural regulation, apatite-inducing mechanism and in vivo investigation of microwave-assisted hydrothermally treated titania coating.

Owing to the poor bioactivity of microarc oxidation (MAO) coating and the rapid activation ability of the microwave hydrothermal (MH) technique, MH treatment was applied to optimize the in vivo interface status between MAO-treated titanium and bone. In this study, consequently, new outermost layers were prepared using hydroxyapatite (HA) nanorods, HA submicron pillars or sodium titanate nanosheets. The results revealed that the NaOH concentration significantly influenced the surface structure and phase constitution of the MAO samples. Moreover, on enhancing the NaOH concentration, the number of HA phases was decreased. Further, the influence of the NaOH concentration on the interfacial bonding strength was insignificant for concentrations ≤0.5 mol L−1. Transmission electron microscopy (TEM) analysis showed that the induction of apatite was accompanied by the dissolution of the HA crystals and there was excellent crystallographic matching with the HA crystals. The in vitro and in vivo analyses revealed that the MH-treated MAO sample with the HA nanorods possessed superior apatite-formation ability and osseointegration, including a small amount of soft tissue and optimal bone–implant interfacial bonding force, thus signifying strong potential for the optimization of the bone–implant interfacial status.

The The variable size consideration of hydroxyapatite extracted from bovine bone at different temperature furnaces

Current bone regeneration surgeries focus on regenerating damaged bone tissue structures rather than replacing them. Bone-derived hydroxyapatite (HAP) is a natural bone component with good bone resilience, emerging and a promising bone graft material. Factors in the synthesis process are very important to the properties of hydroxyapatite. The purpose of this study is to assess the effect of three different furnaced temperatures on the size and phase purity of the HA crystal. The research consists of the following two stages: after combining physical and chemical methods in the first period to eliminate most of the organic components; bones continue to be heated at temperatures of 600oC, 700oC and 800oC to create the various size of HA crystals in bone particles. Product composition and size of HA crystal are determined by TGA, XRD, FTIR, SEM, EDX methods. The results show that crystal size and phase purity can be controlled and increased with the temperature. In particular, the HA crystal size did not change significantly in the range of 600◦C but increased 10-times above 700◦C. Single crystal HA is expected to form in the range of 600 - 700◦C. After the sample was heated to 600◦C, the organic compounds such as blood and bone marrow were completely burned. In addition, two trace elements, Na and Mg, were not completely removed as in other cases but were still retained inside the bone particle. The Ca/P ratio is 1.63 is similar to the Ca/P ratio found in human bones.

Impact of Socket Preservation Technique Using Autogenous Dentin Graft and Hydroxyapatite Crystals on Primary Stability of Dental Implants in Same Individuals: A Pilot Study

A pilot study was conducted to analyze and compare the stability of dental implants using 2 different graft materials (autologous dentin graft and an alloplastic hydroxyapatite [HA] crystal) in the same patient. As far as we know, this study is first of its kind where socket preservation has been done using 2 different grafts in the same patient. Ten patients undergoing extraction of at least 2 teeth were selected. Atraumatic extractions were performed. Out of the 2 extraction sockets, 1 was grafted with autogenous tooth graft and other with HA crystals. Computed tomography scan was performed 3 months after grafting to evaluate bone mineral density. Primary implant stability was measured using resonance frequency analysis. It was observed that among both sites, autogenous tooth grafted sites showed better results.

Improvement in the surface properties of stainless steel via zein/hydroxyapatite composite coatings for biomedical applications

Although stainless steel is renowned for its wide use as a biomaterial, but relatively higher corrosion rate in physiological environment restricts its clinical applications. To overcome the corrosion resistance of stainless steel bio-implants in physiological environment and to improve the osseointegration behavior we developed zein/hydroxyapatite (HA) composite coatings deposited on stainless steel substrate by Electrophoretic Deposition (EPD). The EPD parameters were optimized using the Taguchi Design of Experiment (DoE) approach. The EPD parameters such as the concentration of bio-ceramic particles in the polymer solution, applied voltage, and deposition time were optimized on stainless steel substrates by applying mixed design orthogonal Taguchi array. The coatings were characterized by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and wettability studies. SEM images and EDX results indicated that zein/HA coating was successfully deposited on stainless steel substrates. The wettability and roughness studies elucidated the mild hydrophilic nature of the zein/HA coatings, which confirmed the suitability of the developed coatings for biomedical applications. Zein/HA coatings improved the corrosion resistance of bare 316L stainless steel. Moreover, zein/HA coatings showed suitable adhesion with the 316L SS substrate for biomedical applications. Zein/HA coatings developed dense HA crystal upon immersion in simulated body fluid, which confirmed the bone binding ability of the coatings. Thus, the zein/HA coatings presented strong potential to be considered for orthopedic applications.

In Ukrainian

These studies are aimed on the development of bioactive complex glass-ceramic calcium-phosphate-silicate materials, which are characterized by a reduced fusion with bone tissue in vivo. The aim of this work is to determine the effect of the level of resorption of complex calcium-phosphate-silicate materials and free surface energy on the nature of their binding to albumin in vitro. The calcium ion yield from the material after exposure to distilled water, after one, five, and 15 days, and after exposure in 10 % -albumin solution, after 5 days, was carried out by flame atomic absorption spectrometry using an Agilent AA 240FS device.The surface microrelief was evaluated by the average mean of the profile (R a ) and determined using a Surtronic 3+ profilometer. The value of the free energy of the surface for complex materials was determined after exposure to albumin by the Owens-Wendt-Rabel-Kaelble method. Histological examinations were performed using an Olympus BX63 light microscope. The structure of cells and intercellular fluid was recorded using a digital camera DP73 (Olympus) and software “Cell Sens Dimention 1.8.1”. Samples of the femur of rats, 30 days after implant implantation, which was made of the developed glass-ceramic material, were stained with Weigertpicro-fuchsin and eosin, Van Giesonpicro-fuchsin. To obtain the initial model glasses, the R 2 О–CaF 2 –RO–RO 2 –R 2 O 3 –R 2 O 5 –MoO 3 –SiO 2 system was selected as the basis of glass-ceramic materials, and 5 compositions were synthesized at the temperature of 1250÷1350 °С. To obtain combined glass-ceramic materials, model glass powders were used with addition of 5 wt. % (per 100 wt. % model glass) yttrium stabilized zirconia (DTS 1). The powders were pressed using carboxymethyl cellulose as a binder and fired at 750÷800 °C for 15 minutes. The samples obtained were characterized by the presence of hydroxyapatite crystals in an amount of 50÷60 vol. %. The solubility of the developed materials in water is determined by the properties of the glass-phase (the degree of silicon-oxygen skeleton bonding) and the hydroxyapatite content has been found. The process of binding calcium to albumin (the mass fraction of bound calcium in a solution of 15.67 mg/dm 3 ) for the developed materials is determined by the characteristics of the surface of the materials (FSE = 74.6 mJ/m 2 , R a = 3.4 mcm), the features of their structure (f Si = 0.28, the number of HA crystals = 60 vol. %, with a crystal size of 1.0 μm) and the nature of dissolution. An in vivo study of the samples confirmed the possibility of creating biocompatible materials with a reduced splicing time with bone tissue. As a result of an experimental study using histological methods, it has been determined that the ASZ-5 material is biocompatible, characterized by osteoinductive and osteoconductive properties.

Improvement in Ca and P incorporation in the coating on Ti by gas-assisted electrical discharge coating

Electrical discharge coating (EDC) has been applied to prepare a Ca and P-containing layer on Ti as implant applications. This study aimed to enhance Ca and P incorporation in the coating by absorbing HA on gas using gas-assisted perforated electrodes. The effects of gas flow rate and electrode rotational speed on the coating composition and coating thickness were investigated. Using the gas-assisted perforated electrodes at an appropriate gas flow rate (0.02 L/min) enhanced the Ca and P amount in the coating. In addition, an increase in the rotational speed of the electrode decreased the Ca and P amount in the coating. The coating thickness decreased with increasing electrode rotational speed. The EDC-treated Ti exhibits higher surface hardness and corrosion resistance than Ti. After hydrothermal treatment, the needle and prism HA crystals precipitated on the coating surface, exhibiting hydrophilic property. Furthermore, the hydrothermal treatment slightly improves the corrosion resistance of the EDC-treated Ti.

Blue emissive properties of pure and sodium acid phthalate doped hippuric acid crystal for NLO applications

Non linear optical single crystals of pure and Sodium acid phthalate doped Hippuric acid (SAPHA) crystals were grown in room temperature by slow evaporation method, with the vision to improve the properties of the crystals. Intensities of Powder X-ray diffraction peaks of sodium acid phthalate doped HA reveal that these dopants enhanced the crystallinity. The FTIR analysis is used to study the functional groups. The UV–Visible analysis is used to find the level of transmission and range of absorption of the crystals. The second harmonic generation (SHG) crystal was tested by Kurtz and Perry powder method using Nd:YAG laser and the result confirms that the grown crystal has SHG efficiency 1.05 times more than KDP crystal. The fluorescence study performed for pure and doped HA crystal. The Thermogravimetric analysis confirms the stability of grown crystals. The dielectric response of title crystal was analyzed in the frequency range of 10–100 kHz for four different temperatures at 32 °C, 50 °C, 75 °C, and 100 °C. The hardness of the crystals was determined by Vicker’s Microhardness test.