Hydroxyapatite Phase Research Articles

Development of a Novel Formulation of Bioactive Glass Based Calcium Phosphate Cement for Bone Grafting

AbstractParticulate bone grafting material can travel from the implantation site and diminish the magnitude of required bone formation response and hence its effectiveness. An easily prepared moldable graft that rapidly sets rigid in situ would alleviate this problem and in this study, such an injectable bone graft material is presented. By combining calcium phosphate (CP) salts with a bioactive glass (BG) mixed with a 2.5% Na2HPO4 solution a novel BG‐based calcium phosphate cement (CPC) is produced. Immersion in Tris buffer and simulated body fluid (SBF) solutions result in the rapid generation of octacalcium phosphate (OCP) and hydroxyapatite (HA) phases – a pre‐requisite for “bioactivity”. Cement‐conditioned media does not result in any cytotoxic potential with respect to MTT activity, DNA content, or alkaline phosphatase activity with an osteoblastic cell line. Application of the cement into standardized surgical defects in the minipig mandible results in short‐term, moderate irritation at 3 and 6 weeks and complete replacement of cement with new bone at 12 weeks.

Electrophoretic Deposition of Calcium Phosphates on Carbon-Carbon Composite Implants: Morphology, Phase/Chemical Composition and Biological Reactions.

Despite a long period of application of metal implants, carbon-carbon medical composites are also widely used for bone defect prosthesis in surgery, dentistry, and oncology. Such implants might demonstrate excellent mechanical properties, but their biocompatibility and integration efficiency into the host should be improved. As a method of enhancing, the electrophoretic deposition of fine-dispersed hydroxyapatite (HAp) on porous carbon substrates might be recommended. With electron microscopy, energy dispersion X-ray and Raman spectroscopy, and X-ray diffraction, we found that the deposition and subsequent heat post-treatment (up to the temperature of 400 °C for 1 h) did not lead to any significant phase and chemical transformations of raw non-stoichometric HAp. The Ca/P ratio was ≈1.51 in the coatings. Their non-toxicity, cyto- and biocompatibility were confirmed by in vitro and in vivo studies and no adverse reactions and side effects had been detected in the test. The proposed coating and subsequent heat treatment procedures provided improved biological responses in terms of resorption and biocompatibility had been confirmed by histological, magnetic resonance and X-ray tomographic ex vivo studies on the resected implant-containing biopsy samples from the BDF1 mouse model. The obtained results are expected to be useful for modern medical material science and clinical applications.

Mechanical Grinding of Hydroxyapatite and Its Interaction with Titanium

The development of promising biocompatible composites based on hydroxyapatite with a metallic component is of great interest to researchers. This article describes the synthesis of hydroxyapatite powder by the hydrolytic method and presents the results of mechanical grinding of hydroxyapatite powder. Additionally, in order to study the interaction between titanium and hydroxyapatite powders, the results of their thermal treatment in the temperature range of 600–900 °C are presented. As a result of the hydrolytic method, a powder consisting of Ca5(PO4)3(OH) and CaO phases with a fraction of 400–600 μm was obtained. According to the results of mechanical grinding, it was determined that with an increase in grinding time from 30 to 120 min, the intensive main diffraction lines corresponding to hydroxyapatite decrease. During the thermal treatment of titanium and hydroxyapatite powders, titanium oxidizes forming suboxides and titanium dioxide (TiO2). At higher temperatures, the hydroxyapatite phase disappears from the mixture, and titanium oxide, calcium phosphate compound, and small amounts of calcium titanate and titanium hydrophosphate are present.

Effect of Silver Content and T4 Treatment on the In Vitro Degradation Behavior of Gasar Porous Mg–Ag Alloy

Mg–Ag alloy has potential as a material for bone tissue repair, but the faster degradation rate in vivo limits its use in medical applications. In this study, pure Mg and Mg99.5Ag0.5 alloy with a porous structure are prepared using the metal/gas eutectic unidirectional solidification method (Gasar process). The influence of introducing Ag on the degradation behavior of porous Mg99.5Ag0.5 and pure Mg is investigated. The addition of Ag increases the compressive strength and elastic modulus of the material. The corrosion resistance of as‐cast Mg99.5Ag0.5 alloy decreases due to localized aggregation of Ag in the alloys. Therefore, the T4 (solution treatment) is chosen for the Mg99.5Ag0.5 alloy. After T4 treatment, due to the uniform distribution of Ag atoms in the alloy, the corrosion behavior on the alloy surface is more uniform, and a denser Mg(OH)2 passivation layer is formed on the surface, which reduces the degradation rate of Mg99.5Ag0.5. Importantly, insoluble Ca–P compounds in the form of hydroxyapatite (HA) phases gradually grown on passivated layers of porous T4 Mg99.5Ag0.5 contribute to bone growth. This indicates the feasibility of using the T4 Gasar porous Mg99.5Ag0.5 alloy as a potential tissue engineering scaffold.

Research on column adsorption of Zn<sup>2+</sup> by hydroxyapatite granules

Hydroxyapatite (HAp) granules were fabricated successfully from HAp powder and polyvinyl alcohol (PVA) additive by sintering method. The characterization of material was analyzed by color, durability in the water, XRD, EDX, SEM and BET. The obtained HAp granules were white, single phase of HAp, with specific surface area of 73 m2/g, size of granule about (2 × 10) mm. HAp granules were used for the removal of Zn2+ ions from aqueous solution. The effect of factors on the Zn2+ adsorption property was investigated. The adsorption efficiency and capacity obtained 77.15 % and 2.57 mg/g, respectively at suitable batch adsorption condition: HAp granule mass of 0.5 g/ 50mL solution, initial concentration of 20 mg/L Zn2+, contact time 40 minutes and pH0 5.7 at 30 oC. The adsorption efficiency reached about 99.55 % at suitable column adsorption condition: contact time of 3,5 min, flow rate of 14 mL/min, adsorption zone height of 4Ф (Ф = 2.5 cm), initial concentration of 20 mg/L Zn2+, HAp granule mass of 11.9 g/ 2L solution, pH0 5.7 at 30 oC.

Densification of hydroxyapatite through cold sintering process: Role of liquid phase chemistry and physical characteristic of HA powder

Hydroxyapatite is a well-known bioactive material widely employed in bone regeneration applications. Densifying hydroxyapatite at the nanoscale remains challenging with conventional sintering methods. This investigation focuses on the densification of commercially available nano-hydroxyapatite powders through the cold sintering process, utilizing water, acetic acid, and phosphoric acid solutions as transient liquids under 360 MPa pressure at 200 °C. The study systematically examines the influence of physical parameters of hydroxyapatite powder, liquid nature, and ionic concentrations of acid solutions on densification and microstructural characteristics. The relative density of consolidated samples varied with respect to the ionic concentration of the acid solution. Notably, a maximum relative density of 90% has been achieved for hydroxyapatite cold sintered using 2 M phosphoric acid solution without changing the original phase of hydroxyapatite. Overall, this study offers valuable insights into the impact of liquid chemistry on the densification of hydroxyapatite using the cold sintering technique.

Effect of temperature and time on the synthesis of calcium phosphate obtained by microwave hydrothermal method

Bioceramics are materials used in biomedical devices for bone replacement, and calcium phosphate derivatives are widely used in cases of bone defect repair. The aim was to evaluate the influence of temperature and time on the synthesis of calcium phosphate obtained by the microwave hydrothermal method on its structural and morphological characteristics with a view to application as a bone graft. The calcium phosphate powders (calcium octophosphate, hydroxyapatite and calcium triphosphate) were produced using the microwave hydrothermal method. To obtain the calcium phosphate powders, aqueous solutions of Ca (OH)2 and H3 PO4 were used and subjected to the microwave hydrothermal method at temperatures of 110°C and 130°C for 30 and 60 minutes, then calcined at 700°C for 1 hour and characterized using XRD, FTIR, SEM, particle size distribution, apparent density, and apparent porosity. The results obtained by the techniques confirm crystalline and morphological modifications, and homogeneous distribution of the particles, and the phases of interest, octophosphate, hydroxyapatite and calcium β-triphosphate, were identified. The formation of the β-TCP phase was predominant in the samples in which the microwave hydrothermal synthesis was carried out over a longer time and at a higher temperature. It was found that the proposed synthesis method was effective in terms of time/temperature, offering advantages over conventional techniques, such as improving the primary characteristics for choosing a biomaterial to be used in cases of bone regeneration.

Crucial Chemical Revelations in 45S5 Bioactive Glass via Sequential Precursor Integration Order.

Among the wet chemical nanoparticle fabrication techniques, the sol-gel process happens through hydrolysis and subsequent polycondensation reactions. The bioactive glass known as the 45S5 SiO2-Na2O-CaO-P2O5 quaternary system has intricate chemistry, yet its advantages benefit the biomedical field on an enormous scale. The order in which the ethanol and TEOS inclusions are exchanged was investigated in this work because it has a direct impact on the early hydrolysis process. Another strategy involves adding phosphate species to the sol before gelation, modifying the network chemistry, and interpreting the findings. Adding phosphate species before gelation in the biomaterial (E-Si-P) resulted in the formation of hydroxyapatite and other calcium silicate phases at 800 °C. Swapping ethanol and TEOS biomaterials (E-Si and Si-E) resulted in the sodium-calcium silicate phase only. Si-E with strong Si-O-Si siloxane rings demonstrated superior mechanical stability, hemocompatibility, and bioactivity. This compact Si-O-Si decreased the surface area of Si-E. XPS spectra revealed that E-Si-P has the lowest Na 1s binding energy (BE) and the highest BE for Si 2p. More Si-O-/Si-OH groups formed by E-Si make the network weak and decrease the surface area and protein adsorption. These differences significantly influenced the morphology, surface properties, mechanical studies, and compatibility test. This study has further unraveled the protocol to design a biomaterial with mechanical stability and load-bearing ability. In addition, the appropriate protocol to yield the desired property-rich biomaterial with preserved bioactivity, mechanical stability, cytocompatibility, as well and surface porosity has been elaborated in detail.

Characterization, bioactivity, antibacterial and cytotoxicity of inexpensive soda-lime-silica glass/tetracalcium phosphate composites

Composite biomaterials were created by sintering soda-lime-silica glass powder and tetracalcium phosphate powder. Sintering of the samples at 1200 °C/2h led to the formation of wollastonite, calcium phosphate, and cristobalite before soaking in simulated body fluid (SBF). However, after soaking for two weeks in SBF the hydroxyapatite, wollastonite, and cristobalite phases appeared with relatively intense in hydroxyapatite phase on sample surfaces. The microstructure shows micro-scale particles on the sample surface after soaking in SBF. The bulk densities and porosities were within 1.82453–1.9672 g/cm3 and 15.0621–34.1657 % respectively whereas compressive strength values were between 42.79 and 111.26 MPa. Since the increase of the porosity in the direction of high addition of phosphate portion while strengths were high in opposite values. The biocompatibility in SBF increases with increasing the SLS glass portion and the SEM micrographs show fine spherical crystals, within 20–200 nm, of hydroxyapatite phase on composite surfaces. The FTIR spectrum after soaking in SBF indicates the presence of phosphate bands in all samples and the intensity of these bands increases as the SLS glass percentage increases. The degradation of composite samples decreases in the direction of an increase in the phosphate portion which led to a decrease in the porosity and an increase in both density and strength. Pseudomonas aeruginosa and Staphylococcus aureus, the two examined bacteria, both showed the establishment of growth inhibition zones in the disk diffusion assay. All samples were shown to be biocompatible by the cytotoxicity test conducted on the human normal fibroplast cell line (BJ1). In light of this, the cytotoxicity analysis demonstrated that the highest soda-lime-silica glass sample (SLP55), which has potential uses in the dental and bone fields, was entirely safe for use with the human normal fibroplast cell line (BJ1).

Probing the influence of strontium doping and annealing temperature on the structure and biocompatibility of hydroxyapatite nanorods.

Among numerous biologically important metal cations, strontium (Sr2+) has received much attention in bone tissue regeneration because of its osteoinductive properties combined with its ability to inhibit osteoclast activity. In this study, strontium-doped hydroxyapatite (Sr-HAp) nanorods with varying molar ratios of Ca : Sr (10 : 0, 9 : 1, 5 : 5, 3 : 7 and 0 : 10) were synthesized using the chemical precipitation technique. The synthesized Sr-HAp nanostructures were characterized using powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy, energy dispersive X-ray spectroscopy, and Raman and Fourier transform infrared (FTIR) spectroscopies to understand their structural and morphological features, and composition. XRD results revealed the formation of HAp nanostructures, whose unit cell volume increased as a function of the dopant level. The reaction process investigation showed the formation of hydroxyapatite (HAp), strontium apatite (SAp) and various Sr-HAp phases. FESEM micrographs displayed the morphological transformation of Sr-HAp from nanorods to nanosheets upon increasing the dopant level. In the FTIR spectra, the bands of the PO43- group shifted towards a lower wavenumber upon increasing the dopant concentration in Sr-HAp that signifies the structural distortion due to the presence of a large amount of strontium ions. The peaks of PO43- and OH- vibrations in the Raman spectra were further analysed to corroborate the structural distortion of Sr-HAp. Selected area electron diffraction patterns obtained using TEM reveal the reduced crystallinity of Sr-HAp due to Sr-doping, which is in line with the XRD results. Finally, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed that the synthesized Sr-HAp has no toxic effect on the survival and growth of mesenchymal stem cells. In summary, the synthesized novel Sr-HAp nanorods exhibit great promise for bone tissue engineering applications.

Impacts of pre-treatment methods on the morphology, crystal structure, and defects formation of hydroxyapatite extracted from Nile tilapia scales.

The comprehensive control of hydroxyapatite (HAp), involving morphological and structural variations, particle sizes, and defect formations, has garnered considerable attention for its versatile functionalities, rendering it applicable in diverse contexts. This work examined the shape, structure and optical characteristics, and defect formation in hydroxyapatite (HAp) extracted from Nile tilapia (Oreochromis niloticus) scales with various pre-treatments through experiments and density functional theory (DFT) calculations. Utilizing scanning electron microscopy, our findings revealed that dried fish scales (FS-D) exhibited a layered pattern of collagen fibers, while boiled fish scales (FS-B) had smoother surfaces and significantly reduced collagen content. After calcination, the FS-D sample produced nanorods with an average length of 150 ± 44 nm, whereas the FS-B samples yielded agglomerated spherical particles whose size increased with the rising calcining temperature. In-depth analysis through X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the presence of biphasic calcium phosphates in the FS-B samples, while the FS-D sample presented a pure HAp phase. The boiled fish scale calcined at 800 °C (FS-B800) exhibited an optical band gap (Eg) of 5.50 eV, whereas the dried fish scale calcined at 800 °C (FS-D800) showed two Eg values of 2.87 and 3.97 eV, as determined by UV-visible spectroscopy. DFT calculations revealed that the band gap of 3.97 eV correlated with OH- vacancies, while that of 2.87 eV indicated Mn-substituted HAp, explaining the blue powder. The Eg value for the white powder resembled pure HAp, S- and Cl- substituted OH- vacancies, and various cations substituting Ca sites of HAp. Different pre-treatment procedures influence the characteristics of HAp, offering opportunities for applications in bone replacement and scaffolds for bone tissue engineering.

Densification of transparent hydroxyapatite ceramics via cold sintering process combined with biomineralization

We report for the first time transparent hydroxyapatite (HAp) ceramics densified using a cold sintering process and biomineralization. Under a uniaxial pressure of 800 MPa at 180 °C, granular HAp nanoparticles mixed with simulated body fluid were densified up to 98.5% relative density. During the densification, pseudo-biomineralization occurred among the HAp nanoparticles, leading to the precipitation of a new HAp phase. Additionally, the transformation of granular HAp nanoparticles into nearly circular grains produced fine microstructures with uniform and nanosized grains, reducing light scattering. As a result, the transmittance of 81.6% at λ = 550 nm was achieved. Transparent HAp exhibited Vickers hardness (3.88 ± 0.22 GPa), fracture toughness (0.62 ± 0.03 MPa·m1/2), biaxial flexural strength (41.69 ± 1.23 MPa), and Young's modulus (78.1 ± 2.04 GPa). These findings will pave the way for the fabrication and potential applications of transparent ceramics at low temperatures.

Densification of Calcium Phosphate from Biogenic Waste for Biomedical Application

Introduction: Calcium phosphate-based biomaterial is commonly employed in biomedical applications such as dental applications, bone substitution and filler tissue engineering. Its excellent biocompatibility and potential bio-implant material have attracted many researchers to broaden their hydroxyapatite (HA) studies. Methods: The present work used waste eggshells as the source of calcium precursor to synthesize HA via a solid-state reaction. The eggshells were calcined at 700°C and mixed with the phosphate precursor, dicalcium phosphate dihydrate (DCPD). Following this, the mixture was ball-milled at 400 rpm for 2h and then heat treated at 800°C to produce pure eggshell-derived HA powder. The synthesized HA powder was then consolidated by uniaxial pressing (~6.5 – 7.1 tons) and sintered at 4 different temperatures of 1100°C, 1150°C, 1200°C and 1250°C. Results: From the XRD analysis of the sintered HA samples, it was found that an increase in sintering temperature up to 1250°C did not affect the phase stability of the HA phase. Besides that, grain size, relative density and hardness of the sintered HA samples were also increased with sintering temperature. It was observed that HA dense sample prepared by compacting at 7.1 tons followed by sintering at 1250°C showed the best combination of mechanical properties among all samples with a relative density of 94.6% and a hardness of 3.7 GPa. Conclusion: The current result is significant in supporting the potential of the synthesized eggshell-derived calcium phosphate powder as an ideal alternative for the creation of cost-effective, biocompatible biomaterials for biomedical applications.

AgNPs incorporated in Eu(III)-doped hydroxyapatite biomaterial: Spectroscopic, cytotoxicity, and antimicrobial investigation

This study aimed to synthesize and to characterize hydroxyapatite with antimicrobial action. For the synthesis, the precursors calcium nitrate and phosphoric acid were employed; europium(III), 1 % w/w in relation to calcium(II), was used as spectroscopic probe, to investigate structural alterations. Silver nanoparticles, as antimicrobial agents, were added to the resulting material. Formation of the hydroxyapatite phase was confirmed by X-ray diffraction and vibrational spectroscopy in the infrared region. Incorporation of silver nanoparticles in the material was confirmed by electronic absorption spectroscopy in the ultraviolet–visible region, through the absorption band at approximately 400 nm. Scanning electron microscopy revealed that the material had adequate morphology to induce bone formation. The excitation, emission, and lifetime measurements of the structural probe, europium(III), showed that the hydroxyapatite unit cell had two symmetry sites. Cytotoxicity evaluation in human cells showed that the material was toxic at concentrations above 1250 μg/mL. At 2000 ppm, the material displayed antimicrobial activity against E. coli, but the maximum evaluated concentration was insufficient to verify activity against S. aureus. Therefore, hydroxyapatite bearing silver nanoparticles is a promising material for application in the medical area.

In vitro bioactivity and biocompatibility behaviour of atmospheric plasma sprayed Indian clam seashell derived hydroxyapatite coating on Ti-alloy

Initially, various hydroxyapatite (HA) powders were derived from the Indian clam seashell by the hydrothermal reaction method with varying heating temperatures (700–1000 ℃). Further, the synthesized and agglomerated pure HA powders were sprayed on Ti-6Al-4 V (ELI) alloy to deposit different HA coatings through the atmospheric plasma spraying (APS) technique. In the current work, the in vitro bioactivity and biocompatibility properties of the fabricated HA coatings are examined to find the usefulness of such coated samples for biomedical applications. In the first test, the coatings are exposed to the simulated body fluid (SBF) for 1, 3, and 5 days of duration. The XRD (X-ray diffractometry) and FESEM (Field Emission Scanning Electron Microscopy) analyses of the treated HA coatings reveal the formation of apatite structure, which has grown with immersion time. The biocompatibility of the HA coatings is examined through MTT (3-(4,5-dimethylthiazol-2-yl)− 2,5-diphenyltetrazolium bromide) assay analysis by using human osteosarcoma cell line (MG-63 cell). All the HA coatings are found to show improvement in cell density with an increase in incubation time from 1 to 5 days. From these tests, the seashell-derived HA coatings are found to be both bioactive and biocompatible in nature. The variation in biological properties observed among the HA coatings is due to their different microstructural features resulting from the melting and solidification behavior of the HA feedstocks. As the deposition parameters are kept constant, the synthesis condition of HA powders, such as the reaction temperature, has played a key role in varying the phases and stoichiometry of the resulting coating. With the highest amount of metastable and near stoichiometric HA phase content, the HA-1000 coating has shown the maximum amount of cell proliferation and apatite growth among all. However, from the alkaline phosphatase (ALP) activity test, the HA-800 coating is found to show the maximum ALP expression level. This is attributed to the highest thickness of such coating resulting from the high deposition rate of HA-800 powder. Possibly, the high porosity of HA-800 coating has allowed a good amount of HA material to participate in the reaction process.

Phosphorus-enriched biochar from biogas residue of Eichhornia crassipes: transformation and release of phosphorus

Pyrolysis is an effective technology for treating and utilizing biogas residue. To explore the phosphorus (P) supply capacity of the biochar generated from biogas residue of Eichhornia Crassipes, the P speciation of E. crassipes biogas residue and biomass during pyrolysis (300–700 °C) was analyzed by combining sequential chemical extraction, 31P nuclear magnetic resonance (NMR) and P K-edge X-ray absorption near edge structure (XANES) spectroscopy. Pyrolysis treatment promoted the conversion of amorphous Ca-P phases in biogas residue and biomass into crystalline hydroxyapatite (HAP) phase, which matched the formation of stable HCl-P pools in the biochar derived from biogas residue (AEBs, 22.65–82.04%) and biomass (EBs, 13.08–33.52%) in the process of pyrolysis. Moreover, the total P contents in AEBs (19.43–28.92 mg g−1) were higher than that of EBs (3.41–5.26 mg g−1), indicating that AEBs had a great P reclamation potential. The P release kinetics from AEBs and EBs in water were evaluated via an incubation experiment for 360 h. The P release from both AEBs and EBs conformed to the pseudo-second order kinetics model (R2 > 0.93), but their P release behaviors were different. The P release of AEBs conformed to the diffusion-re-adsorption model, while that of EBs accorded with the diffusion-dissolution model. The diffusive gradients in thin-films (DGT) analysis showed that AEBs could significantly increase soil available P content as compared with EBs. Hence, the biochar produced from biogas residue of E. crassipes via pyrolysis has a good application potential as a P fertilizer.Graphical

A pedagogical approach for the development and optimization of a novel mix of biowastes-derived hydroxyapatite using the Box-Behnken experimental design

The current study details the creation of synthetic hydroxyapatite (HAp) using a combination of catfish and bovine bones (C&B). This is done to design the optimum processing parameters and consolidate instructional strategies to develop HAp scaffolds for biomedical engineering. The HAp produced from the novel mix of the biogenic materials (C&B) was through calcination and supported with the sol-gel technique, sintering, and low-cold compaction pressure. The ideal preparation conditions were identified with the aid of the Box-Behnken statistical design in response surface methodology. To understand the physicochemical and mechanical properties of the formulation, analytical studies on the synthesized HAp were carried out. To establish a substantial relation between the physicomechanical properties of the produced HAp scaffolds, three parameters— sintering temperature, compaction loads, and holding times were used. In the evaluation, the sintering temperature was found to have the greatest impact on the material's physicomechanical properties, with compressive strength (13 MPa), porosity (49.45 %), and elastic modulus (2.216 GPa) being the most enhanced properties in that order. The physicomechanical characteristics of the HAp scaffolds were at their optimal at 900 °C, 1 h 18 min of holding time, and 311.73 Pa of compaction pressure. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) results showed that powders with a dominant HAp phase were produced at all runs, including the optimum run. Therefore, using a computationally effective methodology that is helpful for novelties in biomedical engineering education, this study demonstrates the optimal process for the synthesis of a novel matrix bone-derived HAp, showing the most significant relations liable for manufacturing medically suitable HAp scaffolds from the mixture of bovine and catfish bones.

Guided bone regeneration in long-bone defect with a bilayer mineralized collagen membrane

Bone regeneration for large, critical-sized bone defects remains a clinical challenge nowadays. Guided bone regeneration (GBR) is a promising technique for the repair of multiple bone defects, which is widely used in oral and maxillofacial bone defects but is still unsatisfied in the treatment of long bone defects. Here, we successfully fabricated a bilayer mineralized collagen/collagen (MC/Col)-GBR membrane with excellent osteoinductive and barrier function by coating the MC particles prepared via in situ biomimetic mineralization process on one side of a sheet-like pure collagen layer. The aim of the present study was to investigate the physicochemical properties and biological functions of the MC/Col film, and to further evaluate its bone regeneration efficiency in large bone defect repair. Fourier-transform infrared spectra and X-ray diffraction patterns confirmed the presence of both hydroxyapatite and collagen phase in the MC/Col film, as well as the chemical interaction between them. stereo microscope, scanning electron microscopy and atomic force microscope showed the uniform distribution of MC particles in the MC/Col film, resulting in a rougher surface compared to the pure Col film. The quantitative analysis of surface contact angle, light transmittance and tensile strength demonstrated that the MC/Col film have better hydrophilicity, mechanical properties, light-barrier properties, respectively. In vitro macrophage co-culture experiments showed that the MC/Col film can effectively inhibit macrophage proliferation and fusion, reducing fibrous capsule formation. In vivo bone repair assessment of a rabbit critical segmental radial defect proved that the MC/Col film performed better than other groups in promoting bone repair and regeneration due to their unique dual osteoinductive/barrier function. These findings provided evidence that MC/Col film has a great clinical potential for effective bone defect repair.Graphic abstract

Salvia officinalis-Hydroxyapatite Nanocomposites with Antibacterial Properties.

In the present study, sage-coated zinc-doped hydroxyapatite was incorporated into a dextran matrix (7ZnHAp-SD), and its physico-chemical and antimicrobial activities were investigated. A 7ZnHAp-SD nanocomposite suspension was obtained using the co-precipitation method. The stability of the nanocomposite suspension was evaluated using ultrasound measurements. The stability parameter calculated relative to double-distilled water as a reference fluid highlights the very good stability of the 7ZnHAp-SD suspension. X-ray diffraction (XRD) experiments were performed to evaluate the characteristic diffraction peak of the hydroxyapatite phase. Valuable information regarding the morphology and chemical composition of 7ZnHAp-SD was obtained via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) studies. Fourier-transform infrared spectroscopy (FTIR) measurements were performed on the 7ZnHAp-SD suspensions in order to evaluate the functional groups present in the sample. Preliminary studies on the antimicrobial activity of 7ZnHAp-SD suspensions against the standard strains of Staphylococcus aureus 25923 ATCC, Enterococcus faecalis 29212 ATCC, Escherichia coli 25922 ATCC, and Pseudomonas aeruginosa 27853 ATCC were conducted. More than that, preliminary studies on the biocompatibility of 7ZnHAp-SD were conducted using human cervical adenocarcinoma (HeLa) cells, and their results emphasized that the 7ZnHAp-SD sample did not exhibit a toxic effect and did not induce any noticeable changes in the morphological characteristics of HeLa cells. These preliminary results showed that these nanoparticles could be possible candidates for biomedical/antimicrobial applications.

Study of the Structural-Phase State of Hydroxyapatite Coatings Obtained by Detonation Spraying at Different O2/C2H2 Ratios

This work studies the influence of the composition of an acetylene–oxygen explosive O2/C2H2 mixture on the structure and properties of hydroxyapatite coatings obtained by detonation spraying. The molar ratios of O2/C2H2 were 2.61; 3.03 and 3.35; the explosive charge was between 73 and 77%. The results of X-ray phase analysis showed partial conversion of the hydroxyapatite (HA) phase to the tricalcium phosphate (α-TCP) phase and formation of the amorphous phase during detonation sputtering. The formation of a small amount of the α-TCP phase during detonation spraying of HA is obviously due to structural transformations occurring during the heating of the material by detonation products. In addition, very rapid cooling of molten particles leads to the formation of the amorphous phase. The study results of the microstructure of the cross sections of the formed coatings, conducted using scanning electron microscopy, indicate that an increase in the O2/C2H2 ratio leads to increased porosity in the coatings. Additionally, an increase in the explosive charge by 77% results in the appearance of transverse cracks in the coating.