Bio-inspired Hydroxyapatite/Gelatin Transparent Nanocomposites

Hydroxyapatite(HA)nanoparticles impart outstanding mechanical properties to organicinorganic nanocomposites in bone.Inspired by the composite structure of HA nanoparticles and collagen in bone,a high performance HA/gelatin nanocomposite was first developed.The nanocomposites have much better mechanical properties(elongation at break 29.9%,tensile strength 90.7 MPa,Young’s modulus 5.24 GPa)than pure gelatin films(elongation at break 9.3%,tensile strength 90.8 MPa,Young’s modulus 2.5 GPa).In addition,the composite films keep a high transmittance in visible wavelength range from 0%to 60%of the HA solid content.These differences in properties are attributed to the homogeneous distribution of HA nanoparticles in the gelatin polymer matrix and the strong interaction between the particle surfaces and the gelatin molecules.This protocol should be promising for HA-based nanocomposites with enhanced mechanical properties for biomedical applications.

Effect of Fluoride on the Ion-association of Calcium Phosphate and Crystallization of Hydroxyapatite

Using a titration setup to accurately control the reaction conditions and in situ monitor the reaction,we showed that fluoride exhibited negligible effects on the ion association process of calcium and phosphate and the formation of ACP nanospheres in a buffer solution with constant ionic strength.However,the stability of ACP increased with increasing fluoride concentration,which was ascribed to the inhibitory effect of fluoride on the aggregation of ACP nanospheres and the nucleation of nanocrystals on the surface of ACP nanospheres.Furthermore,fluoride could inhibit the lateral growth of HAP nanosheets and promote the formation of rod-like crystals.These results further improve our understanding of the crystallization pathway of HAP crystals and the regulatory effects of fluoride.

Ionic liquid-assisted preparation of hydroxyapatite and its catalytic performance for decarboxylation of itaconic acid

The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali,we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance.The results showed that the ionic liquid[Bmim]BF_(4) can affect the crystal growth of hydroxyapatite,provide fluoride ion for fluorination of hydroxyapatite,and adjust the surface acidity and basicity,morphology,textural properties,crystallinity,and composition of hydroxyapatite.The[Bmim]BF4 dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system,thus changing the degree of fluoridation of hydroxyapatite.High fluoride-ion concentration can lead to the formation of CaF_(2) and thus significantly decrease the catalytic performance of hydroxyapatite.The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis,leading to different catalytic performance.The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows:a mass ratio of[Bmim]BF4 to calcium salt=0.2:1,a hydrothermal time of 12 h,and a hydrothermal temperature of 130℃.A maximal methacrylic acid yield of 54.7%was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions(250℃ and 2 MPa of N_(2))in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.

Characterization of Hydroxyapatite Extracted from Crab Shell Using the Hydrothermal Method with Varying Holding Times

Hydroxyapatite(HA)is a bio ceramic commonly utilized in bone tissue engineering due to its bioactive and osteoconductive properties.Crab shells are usually disregarded as waste material despite their significant CaCO_(3) content,and have not been widely utilized in the synthesis of HA.This study aims to synthesize and analyze HA derived from crab shells using the hydrothermal method with different durations of holding time.This study utilized precipitated calcium carbonate(PCC)derived from crab shells.With a hydrothermal reactor set at 160℃ and varying holding times of 14(HA_14),16(HA_16),and 18(HA_18)h,a PCC and(NH4)2HPO4 mixture was used to synthesize HA.The synthesis results were analyzed using scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD)tests.This study has accomplished the synthesis of HA from crab shells.Nonetheless,the final product of synthesis still contained CaCO_(3) as an impurity.The prolonged hydrothermal holding time of 14 to 18 h resulted in a reduction of impurities while increasing the percentage of crystal weight and crystallite size of HA.Specimen CH_18 is the best-quality product generated in this study.This specimen produced HA with the highest percentage of crystal weight and crystallite size compared to the other specimens.Furthermore,specimen CH_18 exhibited the lowest concentration of impurities.The Ca/P ratio in this specimen was also the closest to 1.67.The Ca/P ratio,crystallite size,and crystal weight percentage of this specimen are 1.54,19.06 nm,and 99.1%,respectively.

Hydroxyapatite-containing PEO-coating design for biodegradable Mg-0.8Ca alloy: Formation and corrosion behaviour

In this study, the biocompatible protective coating was formed using plasma electrolytic oxidation(PEO) on bioresorbable Mg-0.8Ca alloy. The composition of the formed coating was studied using XRD, SEM-EDX analysis, and micro-Raman spectroscopy. The uniform distribution of hydroxyapatite over the thickness of protective PEO-layer was established. Using traditional(EIS, PDP, OCP) and local scanning electrochemical methods(SVET, SIET with H^(+)-selective microelectrode), the level of protective properties of PEO-layer in a biological environment(mammalian cell culture medium, MEM) was determined. It was established that modification of Mg-0.8Ca alloy surface by PEO contributes to a significant increase in the corrosion resistance of the surface layer, making it possible to control the process of material‘s biodegradation. The maximum local electrochemical activity was recorded after 72 h of testing, while for the uncoated sample,intense corrosion degradation was recorded in the first 12 min of exposure to the cell culture medium. Formation of the PEO-coating results in a twofold decrease in the corrosion current density(2.8·10^(-6)A cm^(-2)) and an increase in the impedance modulus measured at a low frequency(1.7·10^(4)Ω cm^(2)) in comparison with the uncoated material(9.5·10^(-6)A cm^(-2);8.1·10^(3)Ω cm^(2)). The mechanism of material bioresorption was established and a model for biodegradation process of Mg-0.8Ca alloy with hydroxyapatite-containing PEO-coating in MEM was proposed. Analysis of these results and comparing with others obtained by various scientific groups indicate the prospects for application of biocompatible PEO-coating on Mg-Ca alloy in implant surgery.

Influence of Ca/P ratio on the catalytic performance of hydroxyapatite for decarboxylation of itaconic acid to methacrylic acid

Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.

Corrosion behavior of composite coatings containing hydroxyapatite particles on Mg alloys by plasma electrolytic oxidation: A review

Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.

Investigation of the Nd-Ce-Mg-Zn/Substituted Hydroxyapatite Effect on Biological Properties and Osteosarcoma Cells

Cancerous diseases and diseases resulting from bacteria and fungi are some of the pressures that humans face.Therefore,the development of biomaterials that are resistant to cancerous diseases,bacteria,and fungi has become one of the requirements of the medical field to extend the life of the biomaterial and fight pathogens after implanting these materials inside the human body.One of the important biomaterials used in the field of orthopedics is hydroxyapatite.In this research,Nano substituted hydroxyapatite was prepared by the wet precipitation method,including replacing 5%of the calcium ions with neodymium,cerium,magnesium,and zinc ions in cationic substitution.Many tests were carried out to characterize the prepared material.The biological properties were evaluated by examining the resistance of the substituted hydroxyapatite to bacteria and fungi,in addition to testing the effect of the material on normal cells and bone cancer cells.The results showed a new structure of hydroxyapatite after the substitution process and a significant improvement in the biological properties of the prepared biomaterial compared to other researches.

Azoximer bromide and hydroxyapatite:promising immune adjuvants in cancer

Immune adjuvants are immune modulators that have been developed in the context of infectious vaccinations.There is currently a growing interest in immune adjuvants due to the development of immunotherapy against cancers.Immune adjuvant mechanisms of action are focused on the initiation and amplification of the inflammatory response leading to the innate immune response,followed by the adaptive immune response.The main activity lies in the support of antigen presentation and the maturation and functions of dendritic cells.Most immune adjuvants are associated with a vaccine or incorporated into the new generation of m RNA vaccines.Few immune adjuvants are used as drugs.Hydroxyapatite(HA)ceramics and azoximer bromide(AZB)are overlooked molecules that were used in early clinical trials,which demonstrated clinical efficacy and excellent tolerance profiles.HA combined in an autologous vaccine was previously developed in the veterinary field for use in canine spontaneous lymphomas.AZB,an original immune modulator derived from a class of heterochain aliphatic polyamines that is licensed in Russia,the Commonwealth of Independent States,and Slovakia for infectious and inflammatory diseases,is and now being developed for use in cancer with promising results.These two immune adjuvants can be combined in various immunotherapy strategies.

The fabrication of hydroxyapatite mineralized hydrogels for bone tissue engineering

Bone is a complex but orderly mineralized tissue with hydroxyapatite(HA)as the inorganic phase and collagen as the organic phase.Inspired by natural bone tissues,HA-mineralized hydrogels have been widely designed and used in bone tissue engineering.HA is majorly utilized for the treatment of bone defects because of its excellent osteoconduction and bone inductivity.Hydrogel is a three-dimensional hydrophilic network structure with similar properties to the extracellular matrix(ECM).The combination of HA and hydrogels produces a new hybrid material that could effectively promote osteointegration and accelerate the healing of bone defects.In this review,the structure and growth of bone and the common strategies used to prepare HA were briefly introduced.Importantly,we discussed the fabrication of HA mineralized hydrogels from simple blending to in situ mineralization.We hope this review can provide a reference for the development of bone repair hydrogels.

Effect of cetyltrimethylammonium bromide on morphology and porous structure of mesoporous hydroxyapatite

The mesoporous hydroxyapatite （HA） was synthesized by hydrothermal method utilizing cationic surfactant cetyltrimethylammonium bromide （CTAB） as template. The crystalline phase, morphology and porous structure were characterized respectively by different detecting techniques. The results reveal that the particles are highly crystalline hydroxyapatite phase. The surfactant has little influence on the morphology of the crystals, but affects the porous structure obviously. The sample without CTAB has a low surface area not exceeding 33 m^2/g, and no distinct pores can be observed by TEM. While the samples obtained with the surfactant get better parameters. Numerous open-ended pores centered at 2-7 nm spread unequally on the surface of the hydroxyapatite nanorods. The N2 adsorption-desorption experiments show type IV isotherms with distinct hysteresis loops, illustrating the presence of mesoporous structure. When the mole ratio of CTAB to HA is 1：2, the sample has the largest surface area of 97.1 m^2/g and pore volume of 0.466 cm^3/g.

Arginine functionalized hydroxyapatite nanoparticles and its bioactivity for gene delivery

In order to further improve the transfection efficiency of hydroxyapatite nanoparticle （HAp）, arginine functionalized hydroxyapatite （HAp/Arg） was synthesized by hydrothermal synthesis. The morphology, crystallite size and zeta potential of the HAp/Arg were characterized by transmission electron microscopy （TEM）, atomic force microscopy （AFM） and zeta potential analyzer. The loading and protecting properties of HAp/Arg to DNA were tested by electrophoresis. Its cytotoxicity was also measured in Hela cells and HAEC cells by MTT and LDH, and its transfection efficiency was examined by fluorescence microscope and flow cytometry. The results reveal that HAp/Arg is short rod-like and nano single crystal, the mean diameter is 50-90 nm and zeta potential is 35.8 mV at pH 7.4. HAp/Arg to DNA can be condensed by electrostatic effect and protect DNA against degradation in DNase I, and shows high transfection efficiency without cytotoxicity. These results suggest that HAp/Arg can be a promising alternative as a novel gene delivery system.

Synthesis of Crystalline Hydroxyapatite from CaCO_3 and CaHPO_4·2H_2O by Mechanochemical Method

The mixture of CaHPO 4·2H 2O and CaCO 3 was ground in an aqueous system under appropriate conditions to investigate the mechanochemical reaction for the synthesis of crystalline hydroxyapatite (HA) powder. Hydroxyapatite of high crystallinity powder including trace Ca 10 (PO 4) 6CO 3(OH) and Ca 9HPO 4(PO 4) 6OH can be synthesized by mechanical activation without further thermal treatment at a high temperature. The synthesis reaction during the grinding process was almost completed within 1h. The as-ground powder exhibits a particle distribution of 20-100nm in size with a spherical or rodlike morphology. The composition and degree of crystallinity of the mechanochemical synthesized hydroxyapatite powders were coincident with the cement-type hydroxyapatite.

Synthesis and characterization of arginine-modified and europium-doped hydroxyapatite nanoparticle and its cell viability

The arginine-modified and europium-doped hydroxyapatite nanoparticles（HAP-Eu） were synthesized by hydrothermal synthesis.The prepared nanoparticles were characterized by transmission electron microscopy（TEM）,X-ray diffractometry（XRD）,Fourier transform infrared（FTIR） and zeta potential analyzer.The cell viability of HAP-Eu was tested by image flow cytometry.The results indicated that HAP-Eu is short column shapes and its size is approximately 100 nm,its zeta potential is about 30.10 mV at pH of 7.5,and shows no cytotoxicity in human epithelial cells and endothelial cells.

Effects of Nanometer Hydroxyapatite on Proliferation of Periodontal Ligament Fibroblasts

Objective:To investigate possible effects of nanophase powder of hydroxyapatite on proliferation of periodontal ligament cells. Methods: With sol-gel method, the nanophase hydroxyapatite powders were fabricated. These powders were proved nanopaticles by transmission electron microscope. The effects on proliferation of periodontal ligament cell(PDLC) were observed in vitro with MTT [3-(4,5dimethylthiazo;-2-yl)-2,5-diphenytetralium bromide] method. Results: On the 2nd,3rd,4th day after treated with nanoparticles of hydroxyapatite, the proliferate activity of the PDLC increases significantly, compared with those with dense hydroxyaoatite and control but no significant difference could be found between the dense hydroxyapatite and the control. Conclusion: Nanophase hydroxyapatite can promote the regeneration of periodontal tissue.

Cytotoxinic Mechanism of Hydroxyapatite Nanoparticles on Human Hepatoma Cell Lines

Stable and single dispersed HAP nanoparticles were synthesized with chemical method assisted by ultrasonic treatment.HAP nanoparticles were surveyed by AFM and Zataplus.The effect on the Bel-7402 human hepatoma cell lines treated with HAP nanoparticles was investigated by the MTT methods and observation of morphology,and the mechanism was studied in changes of cell cycle and ultrastructure.The result shows that inhibition of HAP nanoparticles on the Bel 7402 human hepatoma cell lines is obviously in vitro.HAP nanoparticles the entered cancer cytoplasm,and cell proliferation is stopped at G 1 phase of cell cycle,thus,cancer cells die directly.

Hydroxyapatite Bioceramic Coatings Prepared by Hydrothermal-electrochemical Deposition Method

The hydroxyapatite（HA） ceramic coating was successfully prepared on Ti6A14V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diffraction. The releationship between crystallinity and depositing temperature was discussed. The microstructures of hydroxyapatite coating were observed by scanning electron microscope. The experimental results showed that the phases, crystaUinity and morphologies of deposits were influenced by depositing temperature （100℃, 120℃, 140℃, 160℃, 180℃ and 200℃, respectively）. The special hydrothermal environment can lower the crystallization temperature of HA. The crystallinity of HA increases firstly and then decreases with the increase of temperature. There is little hydroxyapatite deposited on the Ti6A14V surface when the depositing temperature is 100℃. The HA deposition increases with the increase of the depositing temperature. And the HA morphologies are influenced by the depositing temperature.

Biologically Inspired Self-assembling Synthesis of Bone-like Nano-hydroxyapatite/PLGA-(PEG-ASP)_n Composite: A New Biomimetic Bone Tissue Engineering Scaffold Material

A new biomimetic bone tissue engineering scaffold material, nano-HAI PLGA-（ PEG-Asp ）n composite, was synthesized by a biologically inspired self-assembling approach. A novel biodegradable PLGA- （ PEG-Asp ）n copolymer with pendant amine functional groups and enhanced hydrophilicity woo synthesized by bulk ring-opening copolymerization by DL-lactide（ DLLA） and glycolide（ GA ） with Aspartic acid （ Asp ）-Polyethylene glycol（PEG） alt-prepolymer. A Three-dimensional, porous scaffold of the PLGA-（ PEG- Asp）n copolymer was fabricated by a solvent casting , particulate leaching process. The scaffold woo then incubated in modified simulated body fluid （naSBF）. Growth of HA nanocrystals on the inner pore surfaces of the porous scaffold is confirmed by calcium ion binding analyses, SEM , mass increooe meoourements and quantification of phosphate content within scaffolds. SEM analysis demonstrated the nucleation and growth of a continuous bonelike, low crystalline carbonated HA nanocrystals on the inner pore surfaces of the PLGA- （ PEG-Asp ）n scaffolds. The amount of calcium binding, total mass and the mass of phosphate on experimental PLGA- （ PEG-Asp ） n scaffolds at different incubation times in mSBF was significantly greater than that of control PLGA scaffolds. This nano-HA/ PLGA-（ PEG- Asp ）n composite stunts some features of natural bone both in main composition and hierarchical microstrueture. The Asp- PEG alt-prepolymer modified PleA copolymer provide a controllable high surface density and distribution of anionic functional groups which would enhance nucleation and growth of bonelike mineral following exposure to mSBF. This biomimetic treatment provides a simple method for surface functionalization and sabsequent mineral nucleation and self-oosembling on bodegradable polymer scaffolds for tissue engineering.

Adsorption of Disperse Blue SBL dye by synthesized poorly crystalline hydroxyapatite

The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO3)2and (NH4)2HPO4 reagents in aqueous solution at room temperature. The adsorption experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent dosage, initial dye concentration, solution temperature, and pH. The experimental results show that the percentage of dye removal increases with increasing the amount of adsorbent, until the total discoloration. The adsorption isotherms follow the model of Langmuir with a high adsorption capacity. The adsorption was pH and temperature dependent.

Plasmid-based Stat3 siRNA delivered by hydroxyapatite nanoparticles suppresses mouse prostate tumour growth in vivo

DNA vector-based Stat3-specific RNA interference （si-Stat3） blocks Stat3 signalling and inhibits prostate tumour growth. However, the antitumour activity depends on the efficient delivery of si-Stat3. The effects on the growth of mouse prostate cancer cells of si-Stat3 delivered by hydroxyapatite were determined in this study. RM-1 tumour blocks were transplanted into C57BIJ6 mice. CaCl2-modified hydroxyapatite carrying si-Stat3 plasmids were injected into tumours, and tumour growth and histology were determined. The expression levels of Star3, pTyr-Stat3, Bcl-2, Bax, Caspase3, VEGFand cyclin D1 were measured by western blot analysis. Amounts of apoptosis in cancer cells were analysed with immunohistochemistry and the terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling （TUNEL） assay. The results showed that hydroxyapatite-delivered si-Stat3 significantly suppressed tumour growth up to 74% （P〈0.01）. Stat3 expression was dramatically downregulated in the tumours. The immunohistochemistry and TUNEL results showed that si-Stat3-induced apoptosis （up to 42%, P〈0.01）. The Stat3 downstream genes Bcl-2, VEGFand cyclin DI were also strongly downregulated in the tumour tissues that also displayed significant increases in Bax expression and Caspase3 activity. These results suggest that hydroxyapatite can be used for the in vivo delivery of plasmid-based siRNAs into tumours.