Hydroxyapatite Bioceramics Research Articles

Young's Modulus and Vickers Hardness of the Hydroxyapatite Bioceramics with a Small Amount of the Multi-Walled Carbon Nanotubes.

The Vickers hardness and Young’s modulus of the hydroxyapatite (HA) bioceramics with a small amount of the multi-walled carbon nanotubes (MWCNTs) were studied by using ultramicrotester Shimadzu for dynamic tests DUH-211. Small concentrations of MWCNTs were from 0.05 to 0.5 wt.%. The argon inert atmosphere and vacuum condition were taken for the prevention of the MWCNTs oxidation. The Brunauer–Emmett–Teller (BET) surface area SBET of the HA-MWCNTs composites was determined by thermal adsorption-desorption of nitrogen. It was found that for HA-MWCNTs sintered in the Ar atmosphere, an increase in the concentration of nanotubes up to 0.5 wt.% leads to a decrease in porosity near 3 times in comparison to HA without MWCNTs additives. The small amount of additives of multi-walled carbon nanotubes leads to an increase in hardness of 1.3 times and compression strength of composite and compression strength of composite that is comparable in absolute values with the literature data of enamel hardness (3–5 GPa) and compression strength (95–370 MPa). The absolute values increase close to linearly with the increase of nanotube concentrations. The Young’s modulus of sintered composite slightly changes with the variation of concentrations of nanotubes and close to the enamel (75–100 GPa). The ratio of plastic work to total work and the ratio of elastic (reversible) work to the total work of deformation of composite HA/MWCNTs are practically constant at a studied range of MWCNTs concentration. The additives of the multi-walled carbon nanotubes lead to both an increase in the elasticity index of ~1.5 times and an increase in the resistance to plastic deformation of ~3 times, which improved the tribological performance of the surface. Plastic and elastic (reversible) work slightly changed.

Characterization and Sintering Properties of Hydroxyapatite Bioceramics Synthesized From Clamshell Biowaste

Hydroxyapatite (HA) is a type of calcium phosphate-based bioactive ceramic that resembles the mineral phase of bone and teeth with great potential for bone substitution and biomedical implants. Biogenic-derived HA emerges as a cheap and eco-sustainable alternative to improve waste utilization. However, hydroxyapatite has limited applications due to its apparent brittleness, thus prompting investigation for enhanced sintering properties. In the present study, the combination of calcination and chemical precipitation technique was used to extract hydroxyapatite (HA) from ark clamshells (Anadara granosa). The method successfully produced HA powder with a Ca/P ratio of 1.6 and characteristic bands corresponded to pure HA via Fourier Transform Infrared Spectroscopy (FTIR). The synthesized HA powder was then sintered at temperatures ranging from 1200 °C to 1300 °C, followed by mechanical evaluation of the density, Vickers hardness, fracture toughness and grain size. It was revealed that the samples sintered at 1250 °C achieved a relative density of ~88%, Vickers hardness of 5.01 ± 0.39 GPa, fracture toughness of 0.88 ± 0.07 MPa.m1/2 and average grain size of ~3.7 µm. Overall, the results suggest that ark clamshell synthesized HA (ACS) had the potential to be used as functional bioceramics for biomedical applications. ABSTRAK: Hidroksiapatit (HA) adalah sejenis seramik bioaktif berasaskan kalsium fosfat yang menyerupai fasa mineral tulang dan gigi, berpotensi besar mengantikan tulang dalam implan bioperubatan. HA yang berasal dari biogenik muncul sebagai alternatif yang murah dan eko-lestari dalam menambah baik pengurusan sisa. Walau bagaimanapun, hidroksiapatit mempunyai aplikasi yang terhad kerana mempunyai kerapuhan yang ketara, menyebabkan penyelidikan diperlukan bagi meningkatkan sifat sintering. Gabungan teknik kalsinasi dan pemendakan kimia telah digunakan dalam kajian ini, bagi mengekstrak hidroksiapatit (HA) dari kulit kerang (Anadara granosa). Kaedah ini telah berjaya menghasilkan serbuk HA dengan nisbah 1.6 Ca/P dan jalur puncak sepadan dengan HA tulen melalui Spektroskopi Inframerah Transformasi Fourier (FTIR). Serbuk HA ini kemudian disinter pada suhu antara 1200 °C hingga 1300 °C, diikuti penilaian mekanikal pada ketumpatan, kekerasan Vickers, kerapuhan dan ukuran bijirin. Hasil ujian menunjukkan bahawa sampel yang disinter pada suhu 1250 °C mencapai ~88% ketumpatan relatif, kekerasan Vickers 5.01 ± 0.39 GPa, kerapuhan pada 0.88 ± 0.07 MPa.m1/2 dan purata ukuran butiran ~ 3.7 µm. Secara keseluruhan, dapatan menunjukkan bahawa kulit kerang HA yang disentisis (ACS) berpotensi sebagai bioseramik bagi aplikasi bioperubatan.

Biomimetic and osteogenic natural HAP coated three dimensional implant for orthopaedic application

The excellent biocompatible and osteogenesis ability of multifunctional three-dimensional (3D) polymeric scaffolds have a vital role in bone regeneration application. Our prime focus of the investigation is the synthesis of snail shell-derived hydroxyapatite coated poly[bis(carboxyphenoxy)phosphazene] (PCPP)/poly(ε-caprolactone) (PCL) 3D scaffold. Snail shells are utilized for hydroxyapatite (HAP) synthesis via a modified chemical precipitation method. The interconnected PCPP/PCL polymeric scaffold was fabricated by the conventional solvent-casting/particulate-leaching method. Bioceramic HAP was further coated on the scaffold by the dip-coating technique. The obtained natural HAP from Turritella duplicata has minerals and organic substituents which are essential for biomedical application. HAP reinforcement significantly increases the mechanical property, compressive strength, and porosity of the scaffolds. The SEM image depicted the homogenous dispersion of HAP over the scaffold surface. Mechanical studies of the 3D polymeric scaffold at the 2% TSS-HAP content demonstrated a significant increase in compressive strength with desired porous structure. It showed increasing compressive strength from 1.52 MPa to 2.18 MPa and porosity of 82.26% to 76.18%. Snail shell HAP grafted polymeric scaffold shows mineralization with the formation of bone-like apatite. The HAP grafted bioceramic/polymeric scaffold surface helps in the attachment and proliferation of MG-63 cells. It also explored the biocompatible property and antibacterial against gram-positive/gram-negative bacteria. Overall, the fabricated 3D implant has improved mechanical strength, optimum pore size, and interconnected structure, which helps in mineralization and cancellous bone tissue engineering applications.

Additive Manufacturing of Hydroxyapatite Bioceramic Scaffolds with Projection Based 3D Printing

Hydroxyapatite (HA) bioceramics have garnered considerable attention owing to their applications in the field of bone repair and excellent biocompatibility. Compared to extrusion-based 3D printing, projection-based 3D printing (3DPP) can fabricate parts with complex geometry, high accuracy, and efficiency, which is very promising for bioceramic scaffolds. However, conventional 3DPP using a paste with low viscosity will cause severe shrinkage of the parts after sintering, which makes it unsuitable for bioceramic scaffolds, and a system investigation of the printing process remains insufficient. In this study, we proposed a 3DPP device suitable for bioceramic scaffolds and investigated the additive manufacturing of HA scaffolds. Ceramic paste properties and process parameters of curing, debinding, and sintering were initially examined. The mechanical properties, shrinkage, and biocompatibility in vitro of the sintered samples were further investigated. The obtained results indicate that HA bioceramics with uniform morphology, complex structure, and high accuracy can be manufactured using the 3DPP equipment. HA scaffolds have the mechanical strength of human cancellous bone, while HA scaffolds cultured with osteoblast precursor cells possess strong biocompatibility and can promote osteoblast adhesion, proliferation, and differentiation. These results suggest a promising application of the 3DPP technique in the preparation of bioceramic scaffolds, and the HA scaffolds fabricated using the 3DPP technique exhibit promising potential in fulfilling a constructive role in the biomedical field of human bone regeneration repair.

Thermal and structural properties of sodium, potassium and carbonate doped strontium hydroxyfluorapatite

Ion-doping in hydroxyapatite bioceramics has attracted a lot of interest particularly for biomedical applications in repairing and replacing failure parts of musculoskeletal systems. Thus the multiple doping aims to mimic and resemble the chemical composition of the bone mineral component. Herein strontium hydroxyapatites bioceramics containing sodium Na+ and potassium K+ as cationic substituent and carbonate CO32− and fluoride as anionic substituent were synthesized and characterized by several analysis techniques. Therefore the chemical assays indicated that obtained compounds were less stoichiometric comparably to bone tissues. The X-ray diffraction diagrams and the infrared spectra revealed that pure phases of hydroxyfluorapatite containg the cited ions were obtained. The triple insertion of sodium, potassium and carbonate into the apatite structure leaded to the B-type carbonate apatite. The FE-SEM micrographs of the powders were formed by agglomerates. Moreover, the particles' morphology strongly depends on the ions nature and amount. The D-GTA curves indicated that the heating of the powders from the room temperature to 1000 °C didn't affect the structural and thermal stability of the materials apart from a partial decomposition of the apatite inducing the formation of the β-tristrontium phosphate phase and enhancing the biomaterial character of the materials.

Fabrication of Ti/TiO2(Ca)/hydroxyapatite bioceramic material by micro-arc oxidation and electrochemical deposition

Titanium with a bioceramic hydroxyapatite (HA) coating has been widely used in biomaterials owing to its excellent mechanical characteristics and high osteoconductivity. However, the interfacial strength of Ti/HA prepared by electrochemical deposition (ED) is relatively low because the physical combination is typically inadequate. In this study, to improve the interfacial strength, a micro-arc oxidation (MAO) process with calcium was introduced for preparing a connecting interlayer known as the MAO coating. Pulsed ED was employed to synthesise the HA coating on the MAO surface using an electrolyte with 6 wt% H2O2. Sample characterisations revealed that the MAO coating comprised porous TiO2 (rutile and anatase) with Ca or CaTiO3. The formation of CaTiO3 depends on the current density, reaction time, and concentration of Ca2+, in addition to voltage. The MAO coatings exhibited a higher corrosion resistance than that exhibited by Ti substrates. Furthermore, the HA coating on the MAO coating was confirmed to be plate-like Ca-deficient HA. The final sample had a Ti/TiO2(Ca)/HA structure, and its adhesive strength was approximately double that of the Ti/HA sample. In particular, the MAO coating synthesised at a high Ca2+ concentration exhibited an improved adhesive strength (2.326 MPa). The application of the MAO coating containing Ca as a connecting interlayer is a promising strategy for improving the HA adhesion strength.

Novel 8%‐TiO2‐nanoparticle‐reinforced dense polycrystalline bovine hydroxyapatite bioceramic

AbstractThis study aimed to produce and characterize the microstructure and mechanical properties of dense polycrystalline bovine hydroxyapatite (DPBHA) bioceramics with 5% and 8% of TiO2 nanoparticles after final synthetization for future use in dental implants. Structural characterization was obtained from analyzes by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscope, energy dispersive spectroscopy, and relative density and apparent porosity. The mechanical characterization was performed by measuring the fracture toughness after three‐point flexural strength (FS) test. The microstructural characterization results showed no secondary phase formation and nonhomogeneous nanoparticle dispersion in HA matrix. DPBHA/Np8% (2.9 ± 0.09 g/cm3) exhibited significantly greater density than DPBHA (2.7 ± 0.03 g/cm3) (p = 0.011) and DPBHA/Np5% (2.7 ± 0.05 g/cm3) (p = 0.041). DPBHA (0.9%) had the smallest porosity followed by DPBHA/Np8% (3.4%). DPBHA/Np5% (4.5%) exhibited the greatest proportion of pores. Pure HA (51.7 ± 10.3 MPa) and DPBHA/Np8% (47.4 ± 6.4 MPa) had significant greater FS (p < 0.001) than DPBHA/Np5% (28.8 ± 3.1 MPa). DPBHA (0.43 ± 0.01 MPa m1/2) and DPBHA/Np8% (0.40 ± 0.06 MPa m1/2) presented greater KIc than DPBHA/Np5% (0.23 ± 0.02 MPa m1/2) (p < 0.003; p < 0.007). In conclusion, 8% TiO2 nanoparticle addition to this synthesis would be a promising HA blend, as mechanical properties were similar, and the relative density/apparent porosity showed superior results than those of the DPBHA.

Comparison of Hydroxyapatite/Poly(lactide-co-glycolide) and Hydroxyapatite/Polyethyleneimine Composite Scaffolds in Bone Regeneration of Swine Mandibular Critical Size Defects: In Vivo Study.

Reconstruction of jaw bone defects present a significant problem because of specific aesthetic and functional requirements. Although widely used, the transplantation of standard autograft and allograft materials is still associated with significant constraints. Composite scaffolds, combining advantages of biodegradable polymers with bioceramics, have potential to overcome limitations of standard grafts. Polyethyleneimine could be an interesting novel biocompatible polymer for scaffold construction due to its biocompatibility and chemical structure. To date, there have been no in vivo studies assessing biological properties of hydroxyapatite bioceramics scaffold modified with polyethyleneimine. The aim of this study was to evaluate in vivo effects of composite scaffolds of hydroxyapatite ceramics and poly(lactide-co-glycolide) and novel polyethyleneimine on bone repair in swine’s mandibular defects, and to compare them to conventional bone allograft (BioOss). Scaffolds were prepared using the method of polymer foam template in three steps. Pigs, 3 months old, were used and defects were made in the canine, premolar, and molar area of their mandibles. Four months following the surgical procedure, the bone was analyzed using radiological, histological, and gene expression techniques. Hydroxyapatite ceramics/polyethyleneimine composite scaffold demonstrated improved biological behavior compared to conventional allograft in treatment of swine’s mandibular defects, in terms of bone density and bone tissue histological characteristics.

Effect of hydroxyapatite bioceramics on the growth of osteoblasts and HIF-α/VEGF signal axis in partial hypoxia environment in vitro.

BACKGROUND: Hydroxyapatite bioceramic is a kind of bone implant commonly used in oral clinic treatment. In the early stage of tissue repair, cells will suffer hypoxic due to the interruption of blood supply.OBJECTIVE: Studying the expression of osteoblasts in hypoxic environment will help us to understand the expression and response mechanism of osteoblasts at the implantation site of hydroxyapatite in the early stage of hypoxia.METHODS: MG63 osteoblast cell line was used in this study. The cells of normal group were incubated under normal oxygen and hydroxyapatite ceramics condition. The cells of hypoxia group were incubated under hypoxia (37C, 8% CO, 8% O, 86% N) and hydroxyapatite ceramics condition. Cell proliferation was measured by CCK8 assay. Apoptosis was measured by flow cytometry. Serum alkaline phosphatase (ALP) activity was measured by ALP kit. Hypoxia inducible factor (HIF-) and vascular endothelial growth factor (VEGF) were detected by Western blot.RESULTS: Compared to the normal group, the cells of hypoxia group showed a dramatically higher proliferation ability, especially at 48 h ( 0.05). Due to hypoxia, cell apoptosis was induced, but there is no difference between these two groups. Interestingly, the ALP activity of hypoxia group was higher than that of normal group at 24 h and 48 h ( 0.05). Mechanically, western blot result showed that the protein level of both HIF- and VEGF were up-regulated in hypoxia group.CONCLUSIONS: Under hypoxia condition, hydroxyapatite bioceramics can promote the proliferation of MG63 osteoblasts, elevate the activity of alkaline phosphatase and upregulate HIF- and VEGF expression without effect on apoptosis.

Synergistic Effect of Micro-Nano-Hybrid Surfaces and Sr Doping on the Osteogenic and Angiogenic Capacity of Hydroxyapatite Bioceramics Scaffolds.

BackgroundThe synergistic effect of chemical element doping and surface modification is considered a novel way to regulate cell biological responses and improve the osteoinductive ability of biomaterials.MethodsHydroxyapatite (HAp) bioceramics with micro-nano-hybrid (a mixture of microrods and nanorods) surfaces and different strontium (Sr) doping contents of 2.5, 5, 10, and 20% (Srx-mnHAp, x: 2.5, 5, 10 and 20%) were prepared via a hydrothermal transformation method. The effect of Srx-mnHAp on osteogenesis and angiogenesis of bone marrow stromal cells (BMSCs) was evaluated in vitro, and the bioceramics scaffolds were further implanted into rat calvarial defects for the observation of bone regeneration in vivo.ResultsHAp bioceramics with micro-nano-hybrid surfaces (mnHAp) could facilitate cell spreading, proliferation ability, ALP activity, and gene expression of osteogenic and angiogenic factors, including COL1, BSP, BMP-2, OPN, VEGF, and ANG-1. More importantly, Srx-mnHAp (x: 2.5, 5, 10 and 20%) further promoted cellular osteogenic activity, and Sr10-mnHAp possessed the best stimulatory effect. The results of calvarial defects revealed that Sr10-mnHAp could promote more bone and blood vessel regeneration, with mnHAp and HAp bioceramics (dense and flat surfaces) as compared.ConclusionThe present study suggests that HAp bioceramics with micro-nano-hybrid surface and Sr doping had synergistic promotion effects on bone regeneration, which can be a promising material for bone defect repair.

Enhancing the bioactivity of hydroxyapatite bioceramic via encapsulating with silica-based bioactive glass sol

Although hydroxyapatite (HA) bioceramic has excellent biocompatibility and osteoconductivity, its high chemical stability results in slow degradation which affects osteogenesis, angiogenesis and clinical applications. Silica-based bioglass (BG) with superior biological performance has been introduced into HA bioceramic to overcome this insufficiency; however, the composite bioceramics are usually prepared by traditional mechanical mixture of HA and BG powders, which tremendously weakens their mechanical performance. In this research, BG-modified HA bioceramics were prepared by the use of BG sol encapsulated HA powders. The results showed that introducing 1 and 3 wt% BG allowed the HA-based bioceramics to maintain the high compressive strength (>300 MPa), improved the apatite mineralization activity, and played an important role in cellular response. The bioceramic modified with 1 wt% BG (1BG/HA) remarkably enhanced in vitro cell proliferation, osteogenic and angiogenic activities. This present work provides a new strategy to improve the biological performance of bioceramics and the HA-based bioceramics with 1 wt% BG can be as a promising candidate material for bone repair.

High-strength and tough bioactive Mg-doped hydroxyapatite bioceramics with oriented microchannels

Mg-doped hydroxyapatite (MH) with oriented microchannels was prepared by hot-pressing sintering and pore-forming heat treatment using continuous carbon fibres (CFs) as the pore-forming agent to achieve balanced mechanical and biological properties. The proportion of MH and (Ca, Mg)3(PO4)2 in the microporous bioceramic with inter-microchannel spacing of 400 μm obtained by sintering at 900 °C (900-2P-MH) was 43.9/56.1 (wt%), which could promote degradation. The compressive strength of the MH bioceramics containing oriented microchannels with a suitable pore size (5–14 μm) did not decrease, but increased in comparison with that of a dense MH sample without microchannels. In particular, the compression strength of the MH bioceramic with oriented microchannels formed using single CF units was 53.31% higher than that of the dense ones. The fracture toughness of the MH bioceramics with oriented microchannels increased to 177.42% of that of the dense ones. The strengthening and toughening mechanism includes contributions from the combination of heating and pressing, uniform distribution of microchannels, and in situ formation of continuous micro/nano-MH ceramic tubes. Moreover, the microchannel-containing MH showed noticeably improved apatite mineralisation in simulated body fluid (SBF). Analysis of the rat tibial bone defect model revealed that the relative bone volumes in the cases of the dense MH without microchannels and the MH with microchannels increased by 23.18 and 40.14%, respectively, compared with that of hydroxyapatite. Furthermore, the MH bioceramics with oriented microchannels displayed a moderate reduction in strength owing to degradation after 8 weeks of implantation. The satisfactory osteogenic properties and degradability of the microporous bioceramic can be attributed to Mg2+ doping and oriented microchannels.

Osteoporotic bone recovery by a bamboo-structured bioceramic with controlled release of hydroxyapatite nanoparticles.

While most bone defects can be repaired spontaneously, the healing process can be complicated due to insufficient bone regeneration when osteoporosis occurs. Synthetic materials that intrinsically stimulate bone formation without inclusion of exogenous cells or growth factors represent a highly desirable alternative to current grafting strategies for the management of osteoporotic defects. Herein, we developed a series of hydroxyapatite bioceramics composed of a microwhiskered scaffold (wHA) reinforced with multiple layers of releasable hydroxyapatite nanoparticles (nHA). These novel bioceramics (nwHA) are tunable to optimize the loading amount of nHA for osteoporotic bone formation. The utility of nwHA bioceramics for the proliferation or differentiation of osteoporotic osteoblasts in vitro is demonstrated. A much more compelling response is seen when bioceramics are implanted in critical-sized femur defects in osteoporotic rats, as nwHA bioceramics promote significantly higher bone regeneration and delay adjacent bone loss. Moreover, the nwHA bioceramics loaded with a moderate amount of nHA can induce new bone formation with a higher degree of ossification and homogenization. Two types of osteogenesis inside the nwHA bioceramic pores were discovered for the first time, depending on the direction of growth of the new bone. The current study recommends that these tailored hybrid micro/nanostructured bioceramics represent promising candidates for osteoporotic bone repair.

Amalgamation of nano hydroxyapatite bioceramics for electrical and optical studies

Calcium phosphate minerals (HAp) are the key component of human bones and teeth. The HAp nanorods can perform a good biocompatibility and bioactivity. In this work, HAp powders are synthesized via a simple route by hydrothermal treatment. The resultant HAp samples are rod-like crystalline, where the morphological and particle dimensions can be customized by changing the pH conditions. The prepared HAp powder samples confirmation results are discussed using FT-IR, scanning electron microscopy, XRD, and impedance spectroscopy. FT-IR investigation confirmed that the occurrence of phosphate, carbonate and water molecules for all the samples and the transmittance decreases with pH. The acidic, base and alkaline nature of the synthesised samples are analysed using XRD studies. It results as the pH increases, significant reduction in crystallites size of HAp occurs. The average crystalline size of HAp nanorod is maximum (43.089 nm) for pH4. The SEM images of the synthesized HAp samples obtained, displays nanorods with excellent uniformity which depends on pH value. The particle diameter is estimated in the range of 10 nm to 45 nm. Electrical conductivity and dielectric function are studied using impedance spectroscopy. It can be massively helpful recognition for the presence of conduction mechanism in the synthesised HAp samples. The electrical and the optical properties may be tuned by altering the pH value which is concluded from the current work.

A two-dimensional nanocontainer based on mesoporous polydopamine coated lamellar hydroxyapatite towards anticorrosion reinforcement of waterborne epoxy coatings

Two-dimensional (2D) nanocontainers provide exciting opportunities in anticorrosion application through a skillful combination of delivery functionality for corrosion inhibitors and barrier property of lamellar materials. Herein, we used a versatile emulsion-induced approach to synthesis sandwich-like 2D nanocontainers based on mesoporous polydopamine (PDA) heterostructures on ultrathin bio-ceramic hydroxyapatite (HA) nanosheets. Triblock copolymer and 1,3,5-trimethyl benzene (TMB) synergistically promote the formation of well-defined mesoporous structure. The porous PDA not only provides large amount of contact interface for embedding benzotriazole (BTA), but also serves as another important corrosion inhibitor to achieve active protection effect. In addition, rich functional groups in PDA structure ensure the fine interface compatibility between lamellar HA and waterborne resin, leading to the improvement in terms of coating barrier performance. In comparative evaluation, the composite coatings containing BTA-loaded nanocontainers (1 wt%) exhibit high impedance value (Zf=0.01 Hz) in 3.5 wt% NaCl solutions for 60 days, indicating the long-term anticorrosion properties. Meanwhile, local electrochemical impedance technology proves nanocontainers with BTA loaded obviously inhibited the corrosion reactivity in corrosive microregions. This work puts new insights into designing functional anticorrosion coatings based on the surface construction on 2D materials, which has potential application for improving coating service life in marine environment.

Comparative studies on micromechanical properties and biological performances in hydroxyapatite ceramics with micro/nanocrystalline

AbstractFurther enhancing the comprehensive properties of hydroxyapatite (HA) bioceramics is still a hot topic in biomedical field. The present study was mainly aimed at investigating the special effect of nanoscale feature on the micromechanical properties and biological performances of HA bioceramics. Three kinds of HA bioceramics with micro‐ to nanocrystalline were fabricated by adopting different sintering technologies, that is, conventional sintering (CS), two‐step sintering (TSS), and microwave assisted sintering (MAS). The average grain sizes of HA‐CS, HA‐TSS, and HA‐MAS were 412.49, 264.24, and 122.49 nm, respectively. Among them, HA‐MAS nanoceramics had the lowest water contact angle (28.35°) and the highest surface roughness (92.30 nm). Interestingly, the enhanced crack deflection in HA‐MAS transferred from transgranular cracking to intergranular cracking, resulting into its fracture toughness (1.64 MPa m1/2) increased by 84% compared to HA‐CS. Besides, HA‐MAS underwent the elastic‐plastic deformation without pop‐in cracking, and exhibited no indentation size effect (ISE) phenomenon during the nanoindentation tests. The in vitro biological performances showed that HA‐MAS could promote the bone‐like apatite formation and the osteogenic differentiation of BMSCs. In summary, the construction of nanocrystalline is indeed an effective way to simultaneously improve the micromechanical properties and biological performances of HA bioceramics.

Ecologically Friendly Biofunctional Ink for Reconstruction of Rigid Living Systems Under Wet Conditions.

The development of three-dimensional (3D)-printable inks is essential for several applications, from industrial manufacturing to novel applications for biomedical engineering. Remarkably, biomaterials for tissue engineering applications can be expanded to other new horizons; for instance, restoration of rigid living systems as coral reefs is an emergent need derived from recent issues from climate change. The coral reefs have been endangered, which can be observed in the increasing bleaching around the world. Very few studies report eco-friendly inks for matter since most conventional approaches require synthetic polymer, which at some point could be a pollutant depending on the material. Therefore, there is an unmet need for cost-effective formulations from eco-friendly materials for 3D manufacturing to develop carbonate-based inks for coral reef restoration. Our value proposition derives from technologies developed for regenerative medicine, commonly applied for human tissues like bone and cartilage. In our case, we created a novel biomaterial formulation from biopolymers such as gelatin methacrylate, poly (ethylene glycol diacrylate), alginate, and gelatin as scaffold and binder for the calcium carbonate and hydroxyapatite bioceramics needed to mimic the structure of rigid structures. This project presents evidence from 2D/3D manufacturing, chemical, mechanical, and biological characterization, which supports the hypothesis of its utility to aid in the fight to counteract the coral bleaching that affects all the marine ecosystem, primarily when this is supported by solid research in biomaterials science used for living systems, it can extend tissue engineering into new approaches in different domains such as environmental or marine sciences.

Synthesis and characterization of hydroxyapatite bioceramics from shells of serai snail and mangrove crab in Tanjung Jabung beach: effect of milling process

Hydroxyapatite (HA) is a calcium phosphate compound that is used as a substitute for damaged body tissues, such as bone and dental implants. HA has been synthesized from the serai snail shells and the mangrove crab of west Tanjung Jabung, Jambi province using the dry method. Calcination of the shell at 1000 °C for 12 hours produces CaO, then contact of CaO with air produces Ca(OH)2 which is used as a source of calcium in HA synthesis. Milling time variations for 0 hours, 3 hours, and 6 hours. Sintering at 600 °C for 2 hours produces HA as characterized by using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and particle size analysis using Particle Size Analyzer (PSA). HA which has the highest accuracy of lattice parameters is that which is milling for 3 hours. The diffraction pattern shows the formation of the HA phase accompanied by several other calcium phosphate phases at an angle of 2θ. The FTIR spectrum shows the presence of PO4 3- and OH−groups from HA. PSA analysis shows the longer the milling makes the smaller particle size.

A study of the effects of hydroxyapatite bioceramic extract on Ang/Tie2 system of umbilical vein endothelial cells.

OBJECTIVE: We aimed to investigate the effects of hydroxyapatite bioceramic extract on Ang/Tie2 system and cell proliferation of umbilical vein endothelial cells.METHODS: Human umbilical vein endothelial cells (HUVECs) were used in this research. There are two induvial groups, control group and hydroxyapatite bioceramics extract treatment group. Cell Counting Kit-8 (CCK-8) was used to evaluate cell proliferation. Western blot and real time quantitative PCR (Q-PCR) were used to evaluate the protein and mRNA expression levels of Ang1, Ang2 and Tie2 in Ang/Tie2 system, respectively. All the results were statistically analyzed by Spss19.0. All data were presented as mean standard error of mean (SEM). Student’s t-test was performed to determine the differences among grouped data.RESULTS:Hydroxyapatite bioceramics extract showed no effect on the cell morphology and cell proliferation of HUVECs. Interestingly, we found that both Ang2 and Tie2 protein and mRNA level were markedly increased by hydroxyapatite bioceramics extract.CONCLUSIONS: Hydroxyapatite bioceramic extract showed no cytotoxicity to HUVECs, and might regulate vascular remodeling by mediating Ang/Tie2 system.

Sintering and biocompatibility of copper-doped hydroxyapatite bioceramics

Addition of copper in biomaterials is currently investigated because it is expected to enhance the biological properties of bone graft substitutes. Copper-doped hydroxyapatite (CuHA) ceramics were prepared by high temperature solid-state reaction sintering between HA and CuO powder mixtures. The reaction occurred from 950 °C and copper-doped apatites were obtained up to 5.3 wt% of copper. For higher copper content, the presence of secondary phases of CuO and Cu2O remained in the material. Structural analyses (XRD, FTIR) showed the substitution of hydrogen by copper into the hydroxyapatite hexagonal channels in agreement with the following chemical composition Ca10(PO4)6CuIIzCuIyO2H2-2z-y with x = y + z and 0 ≤ x ≤ 0.7. Dense single phased apatitic HA ceramics containing up to 5.3 wt% of copper could be produced after natural sintering in air at 1100 °C. But, copper-substituted HA was found to be metastable leading to apatitic grains and Cu-rich grain boundaries during cooling to room temperature, which resulted in the formation of CuO grains at the material surface after annealing at 500 °C. Quenching from the sintering temperature was carried out to prevent this phenomenon and obtain ceramics made of single Cu-HA phase with a homogeneous fine grain microstructure. In vitro biological assays using MC3T3-E1 cells indicated that the sintered CuHA ceramics were biocompatible, neither cell adhesion nor proliferation being affected by copper addition. A negative effect on cell differentiation appears only from 5 wt% of copper in HA.