High Hydroxyapatite Research Articles

3D Printing and Property of Biomimetic Hydroxyapatite Scaffold.

The 3D printing of a biomimetic scaffold with a high hydroxyapatite (HA) content (>80%) and excellent mechanical property is a serious challenge because of the difficulty of forming and printing, insufficient cohesion, and low mechanical property of the scaffold. In this study, hydroxyapatite whiskers (HAWs), with their superior mechanical property, biodegradability, and biocompatibility, were used to reinforce spherical HA scaffolds by 3D printing. The compressive strength and energy absorption capacity of HAW-reinforced spherical HA (HAW/HA) scaffolds increased when the HAW/HA ratio increased from 0:10 to 4:6 and then dropped with any further increases in the HAW/HA ratio. Bioceramic content (HAWs and spherical HA) in the scaffolds reached 83%, and the scaffold with a HAW/HA ratio of 4:6 (4-HAW/HA) exhibited an optimum compressive strength and energy absorption capacity. The scaffold using polyvinyl alcohol (PVA) as an additive possessed a good bonding between HA and PVA as well as a higher strength, which allowed the scaffold to bear a higher stress at the same strain. The compressive strength and toughness of the 4-HAW/HA-PVA scaffold were 1.96 and 1.63 times that of the 4-HAW/HA scaffold with hydroxypropyl methyl cellulose (HPMC), respectively. The mechanical property and inorganic components of the biomimetic HAW/HA scaffold were similar to those of human bone, which would make it ideal for repairing bone defects.

Investigation of physical, mechanical and in-vitro bioactivity of bioactive glass-ceramics fabricated from waste soda-lime-silica glass doped P2O5 by microwave irradiation sintering

The ever-increasing generation of waste glass, poses a major environmental challenges due to its large volume and limited recycling options. This research explores a novel sustainable approach to repurposing this waste by transforming it into silicate based bioactive glass-ceramics (SBGCs). The glass waste was recycled into powder form and homogeneously mixed with sodium dihydrogen orthophosphate (NaH2PO4) in the step of 2, 4, 6, 8 and 10 wt % respectively with addition of organic binder and sintered by microwave irradiation approach. The obtained SBGCs were then characterized for its phase constituents, microstructure, physical, mechanical, and in-vitro bioactivity behaviour. The results showed that the samples exhibited considerable density and porosity while both the micro-hardness and compressive strength decreased with increased phosphate content. Sample SLP2% showed optimum hardness and compressive strength of 7.3 GPa and 87 MPa respectively. Combeite was obtained as the major phase while wollastonite and quartz were also detected. The developed SBGCs also showed increased hydroxyapatite (HA) formation after immersion in simulated body fluid (SBF) and displayed good antibacterial capacity when reacted with four bacteria strains. The results obtained indicate that the developed SBGCs might be considered a potential candidate for biomedical applications. However, sample SLP8% is the best sample to serve as bioactive glass-ceramics considering the combination of its high HA and good CHA formation, besides its considerable density and mechanical properties.

Porous hydroxyapatite-titanium dioxide composites prepared by a sol-gel / supercritical CO2-drying combined process

In this work, porous nanostructured materials based on hydroxyapatite (HA) and titanium dioxide (TiO2) were prepared by integrating the sol-gel process and supercritical CO2 drying. These combined processes constitute a synergistic methodology that allows modulating the porosity generated in the gel and preserving it after drying. HA nanoparticles and a pore-generating agent (Polyvinylpyrrolidone) were included without significant modifications to gel consolidation times or integrity by using this methodology. The presence of HA nanoparticles within the TiO2 matrix helped preserving the anatase phase after the calcination stage. No reactivity between the present phases was detected, indicating their successful integration in the final composite material structure, which was one of the most challenging aspects of the research. This allowed HA-TiO2 composites to improve the adhesion of MG63 osteoblast-like cells and their proliferation, being the sample with high HA content (∼37 % wt/wt) the one that presented the best response. The present work puts forward a new way for the synthesis of scaffolds composed of HA and TiO2 with retention of the anatase phase for applications in bone tissue engineering.

Nano-hydroxyapatite filled EPDM nanocomposite: towards green elastomeric thermal insulating coating with superior mechanical, thermal, and ablation properties

ABSTRACT Heat-shielding composite materials containing asbestos has been used for thermal insulation of aerospace rocket motors. However, asbestos has carcinogenic effects on both human and environment. This study was directed to the development of novel elastomeric nanocomposite thermal-shielding coating (asbestos-free); the developed elastomeric nanocomposite was based on hydroxyapatite (HA) nanoparticles (NPs) in an ethylene propylene diene monomer (EPDM) matrix. HA is a bio-ceramic material with 18.5 wt % phosphorus; HA can act as nano phosphorus-based fire extinguisher. HA NPs were synthesized by continuous hydrothermal technique; high crystalline HA nanoplates of 350 nm length, and 100 nm width were successfully developed. HA NPs were integrated into EPDM matrix; uniform dispersion of HA particles was verified via EDAX analysis. The impact of HA NPs on EPDM tensile strength, elongation-at-break, hardness, density, thermogravimetric analysis (TGA), thermal conductivity test, and ablation test was assessed to asbestos fibers. HA/EPDM secured superior mechanical properties compared with Asbestos/EPDM; HA NPs secured an increase the tensile strength, elongation at break by 16.2% and 105.3% respectively. HA with surface hydroxyl groups could be integrated into EPDM matrix via chemical bonding. HA offered novel thermal shielding properties; HA secured a decrease in thermal conductivity coefficient by −21.1%; and the best ablation resistance was increased by + 31.5%. Residual weight was increased by 13%, compared with asbestos fibers.

Preparation and Characterization of a Polyetherketoneketone/Hydroxyapatite Hybrid for Dental Applications.

Here, we developed a new synthetic method for the production of a new class of polymeric inorganic hybrid biomaterial that has potential for dental implant applications and, in general, other orthopedic applications owing to its excellent mechanical properties and biomechanical compatibility. The new hybrid biomaterial is a composite consisting of polyetherketoneketone (PEKK) and hydroxyapatite (HA). This hybrid material boasts several unique features, including its high HA loading (up to 50 wt%), which is close to that of natural human bone; the homogeneous HA distribution in the PEKK matrix without phase separation; and the fact that the addition of HA has no effect on the molecular weight of PEKK. Nanoindentation analysis was used to investigate the mechanical properties of the composite, and its nano/microstructure variations were investigated through a structural model developed here. Through nanoindentation technology, the newly developed PEKK/HA hybrid biomaterial has an indentation modulus of 12.1 ± 2.5 GPa and a hardness of 0.42 ± 0.09 GPa, which are comparable with those of human bone. Overall, the new PEKK/HA biomaterial exhibits excellent biomechanical compatibility and shows great promise for application to dental and orthopedic devices.

Enhancing structural strength and improving cell survival through Polycaprolactone/(gelatin/hydroxyapatite) Core‐Shell nanofibers for tissue engineering

AbstractBone tissue engineering is a practical approach to repairing broken or damaged bones that combines scaffold, cells, and growth factors for treatment. In this study, polycaprolactone (PCL)/gelatin (Ge)/hydroxyapatite (HA) core‐shell nanocomposites have been produced by the coaxial electrospinning method. Coaxial electrospinning is an efficient method for scaffold preparation to provide an interconnected porous fibrous scaffold. The prepared nanocomposite simultaneously benefited from the good mechanical behavior of the core PCL polymer. The desired biological properties also originated from the outer layer of the Ge/HA nanocomposite. Nanofibrous scaffolds' properties were characterized using SEM, TEM, FTIR, TGA, DSC, tensile test, contact angle, and MTT assay. The morphology of the as‐electrospun nanofibers was investigated using SEM and TEM, which revealed a defect‐less fibrous morphology. TEM images showed the core‐shell structure of the prepared scaffold nanofibers. The contact angle test showed that the presence of HA nanoparticles has improved the wettability of fibrous composites. In addition, HA nanoparticles could effectively strengthen the polymer scaffolds. The highest UTS value of 4.1 MPa was obtained in the PCL/(Ge+10%HA) sample. The cytotoxicity results revealed that the prepared scaffolds were utterly biocompatible. Moreover, significant cell proliferation of osteosarcoma cells was observed at high HA contents. The interconnected pores allowed cells to migrate into the scaffolds and grow inside. Based on the obtained results, PCL/(Ge/ HA) core‐shell nanofibers could be a promising candidate for bone scaffolds.

Role of heat treatment of hydroxyapatite powder prior to suspension preparation on the suspension flow behavior

One of the key issues involved in successfully achieving hydroxyapatite (HA) ceramic body without defects using colloidal processing technique, is the preparation of homogeneously high solid loading HA ceramic suspension. This could be achieved via controlling the HA powder properties. The maximum achievable solid loading suspension from the as received HA powder was found to be 14 vol%. The treatment of the as received powder via heat treatment process play a very versatile role in changing the physical properties of the powder. Owing to these changes, well dispersed high solid loading HA suspensions reaching 57 and 59 vol% were successfully prepared from HA powder heat-treated at 1000 and 1100 °C, respectively. The suspensions prepared from the heat-treated powder was found to have acceptable rheological properties for casting processes in terms of low particle interaction, lower number of floc and floc network and higher fluidity.

48 - Calcium Phosphate Nanoparticles Tested on Hydroxyapatite Discs as Remineralising Agent

To investigate the remineralisation properties of novel calcium phosphate nanoparticles (CPNPs) on hydroxyapatite (HA) discs as an alternative substrate model to enamel at different pH levels. Colloidally stable CPNPs (2% w/v) were prepared via co-precipitation of calcium chloride and sodium phosphate, and sodium citrate (100 mM) added post-precipitation as the capping agent. Particle size and morphology were characterised with dynamic light scattering and scanning electron microscopy (SEM). Crystallinity was assessed with Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction, and the Ca/P ratio with inductively coupled plasma mass spectroscopy and total reflection X-ray fluorescence spectroscopy. HA discs were eroded in acetate buffer (0.5 M; pH 4.0) at various timepoints (1, 5, 10, 30 min, and 2, 4 h) to produce a suitably eroded substrate for remineralisation. Their physical differences compared to enamel, together with remineralisation outcome at different pH levels were assessed by Knoop microhardness, surface roughness and step height by a profilometer, SEM and light microscope. Colloidally stable CPNPs of 60 nm, zeta potential -23.3 1.3 mV, with high HA crystallinity and a Ca/P ratio of 1.54 had been produced. HA discs eroded for 2 h showed a 2 m step height and were deemed suitable to be used as a demineralised artificial substrate model for remineralisation. It was established that CPNPs were heterogeneously deposited on the HA discs at pH 9.2, whereas newly precipitated minerals from CPNPs were potentially formed at pH 6.2. Citrate-stabilised CPNPs with high HA crystallinity showed detectable surface remineralisation properties on HA discs.

A Bisphosphonate With a Low Hydroxyapatite Binding Affinity Prevents Bone Loss in Mice After Ovariectomy and Reverses Rapidly With Treatment Cessation.

ABSTRACTBisphosphonates (BPs) are a mainstay of osteoporosis treatment; however, concerns about bone health based on oversuppression of remodeling remain. Long‐term bone remodeling suppression adversely affects bone material properties with microdamage accumulation and reduced fracture toughness in animals and increases in matrix mineralization and atypical femur fractures in patients. Although a “drug holiday” from BPs to restore remodeling and improve bone quality seems reasonable, clinical BPs have long functional half‐lives because of their high hydroxyapatite (HAP) binding affinities. This places a practical limit on the reversibility and effectiveness of a drug holiday. BPs with low HAP affinity and strong osteoclast inhibition potentially offer an alternative approach; their antiresorptive effect should reverse rapidly when dosing is discontinued. This study tested this concept using NE‐58025, a BP with low HAP affinity and moderate osteoclast inhibition potential. Young adult female C57Bl/6 mice were ovariectomized (OVX) and treated with NE‐58025, risedronate, or PBS vehicle for 3 months to test effectiveness in preventing long‐term bone loss. Bone microarchitecture, histomorphometry, and whole‐bone mechanical properties were assessed. To test reversibility, OVX mice were similarly treated for 3 months, treatment was stopped, and bone was assessed up to 3 months post‐treatment. NE‐58025 and RIS inhibited long‐term OVX‐induced bone loss, but NE‐58025 antiresorptive effects were more pronounced. Withdrawing NE‐58025 treatment led to the rapid onset of trabecular resorption with a 200% increase in osteoclast surface and bone loss within 1 month. Cessation of risedronate treatment did not lead to increases in resorption indices or bone loss. These results show that NE‐58025 prevents OVX‐induced bone loss, and its effects reverse quickly following cessation treatment in vivo. Low‐HAP affinity BPs may have use as reversible, antiresorptive agents with a rapid on/off profile, which may be useful for maintaining bone health with long‐term BP treatment. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Characterization of Polycaprolactone Nanohydroxyapatite Composites with Tunable Degradability Suitable for Indirect Printing.

Degradable bone implants are designed to foster the complete regeneration of natural tissue after large-scale loss trauma. Polycaprolactone (PCL) and hydroxyapatite (HA) composites are promising scaffold materials with superior mechanical and osteoinductive properties compared to the single materials. However, producing three-dimensional (3D) structures with high HA content as well as tuneable degradability remains a challenge. To address this issue and create homogeneously distributed PCL-nanoHA (nHA) scaffolds with tuneable degradation rates through both PCL molecular weight and nHA concentration, we conducted a detailed characterisation and comparison of a range of PCL-nHA composites across three molecular weight PCLs (14, 45, and 80 kDa) and with nHA content up to 30% w/w. In general, the addition of nHA results in an increase of viscosity for the PCL-nHA composites but has little effect on their compressive modulus. Importantly, we observe that the addition of nHA increases the rate of degradation compared to PCL alone. We show that the 45 and 80 kDa PCL-nHA groups can be fabricated via indirect 3D printing and have homogenously distributed nHA even after fabrication. Finally, the cytocompatibility of the composite materials is evaluated for the 45 and 80 kDa groups, with the results showing no significant change in cell number compared to the control. In conclusion, our analyses unveil several features that are crucial for processing the composite material into a tissue engineered implant.

Development of three-dimensional printing filaments based on poly(lactic acid)/hydroxyapatite composites with potential for tissue engineering

Injured bone tissues can be healed with scaffolds, which could be manufactured using the fused deposition modeling (FDM) strategy. Poly(lactic acid) (PLA) is one of the most biocompatible polymers suitable for FDM, while hydroxyapatite (HA) could improve the bioactivity of scaffold due to its chemical composition. Therefore, the combination of PLA/HA can create composite filaments adequate for FDM and with high osteoconductive and osteointegration potentials. In this work, we proposed a different approache to improve the potential bioactivity of 3D printed scaffolds for bone tissue engineering by increasing the HA loading (20-30%) in the PLA composite filaments. Two routes were investigated regarding the use of solvents in the filament production. To assess the suitability of the FDM-3D printing process, and the influence of the HA content on the polymer matrix, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were performed. The HA phase content of the composite filaments agreed with the initial composite proportions. The wettability of the 3D printed scaffolds was also increased. It was shown a greener route for obtaining composite filaments that generate scaffolds with properties similar to those obtained by the solvent casting, with high HA content and great potential to be used as a bone graft.

New Insights into Osteointegration and Delamination from a Multidisciplinary Investigation of a Failed Hydroxyapatite-Coated Hip Joint Replacement.

Hydroxyapatite (HA) coatings have become very popular in uncemented total hip arthroplasty (THA). Analysis of retrievals and tissue samples from an HA-coated femoral stem, which failed within 14 months after THA, provides exceptional insights into the failure mechanism, as well as the process of osteointegration of such an implant. Methods: Retrievals were photo-documented. Samples were examined by micro-computed tomography, X-ray diffraction (XRD) and embedded in polymethylmethacrylate for histology. Results: The coating had partially delaminated. The sandblasted surface of the stem was partially polished by the delaminated HA coating, indicating failure before revision. In the tissue samples, the HA coating was well integrated by newly formed bone trabeculae. No adverse biological reaction was observed. XRD analysis showed that residues of the HA coating were still present and could clearly be differentiated from the surrounding bone. Preferential orientation of the HA crystallites could be identified within the newly formed bone, representing a potential mechanical weakness induced either by physiologic strain or by the coating. Conclusion: current HA coatings, relatively thick and made of high crystallinity HA, may be prone to delamination, as also seen in our study. Recent efforts have aimed towards thinner (<1 μm) coatings with nanocrystalline HA structures that possibly relate to lower delamination risks. However, the question arises if HA coatings are beneficial since sandblasted non-coated stems offer similar results without the risk of delamination. XRD not only permits differentiation between the HA from the coating and the HA of the ongrown bone, it also provides new insights into the microstructure of this newly formed bone.

Porous 3D hydroxyapatite/polyurethane composite scaffold for bone tissue engineering and its in vitro degradation behavior

In this study, a novel hydroxyapatite (HA)/polyurethane (PU) composite porous 3D scaffold was developed by in situ polymerization. Aliphatic hexamethylene diisocyanate (HDI) as a nontoxic and safe agent was adopted to produce the rigid segment in PU polymerization. HA powder was compounded in a PU polymer matrix during the polymeric process. The macrostructure and morphology as well as mechanical strength of the scaffolds were characterized by FTIR, XRD and SEM. The results show that the HDI can react mildly with hydroxyl (–OH) groups of polytetramethylene ether glycol and a mild foaming action caused by the release of CO2 gas occurred simultaneously in the reactive process, thus producing a uniform porous structure of HA/PU scaffold. The HA/PU composite scaffold with a high HA content of about 30 wt% has a porosity of more than 60% and a pore size from 100 to 800 μm. After immersed in simulated body fluid, the scaffolds were investigated by weight loss experiments and FTIR. The results show that polymerized component of HA/PU scaffolds degraded gradually in vitro, while HA component presented a classic trend of dissolution then deposition procedure. Three hydrolysis processes may happen in the PU degradation. The HA/PU scaffolds should be a promising material for bone tissue regeneration in clinic.

Polydopamine regulated hydroxyapatite microspheres grown in the three-dimensional honeycomb-like mollusk shell-derived organic template for osteogenesis

Layered osteochondral composite scaffolds are considered as a promising strategy for the treatment of osteochondral defects. However, the insufficient osseous support and integration of the subchondral bone layer frequently result in the failure of osteochondral repair. Therefore, it is essentially important to explore new subchondral bone constructs tailored to support bone integration and healing. In this study, a novel three-dimensional porous biomimetic construct (HA/pDA-OTMS) was successfully developed by polydopamine (pDA) regulating hydroxyapatite (HA) microspheres grown in the honeycomb-like mollusk shell-derived organic template (OTMS). The biomimetic OTMS had good mechanical properties, high toughness, biodegradability and excellent biocompatibility. Moreover, the long-range ordered cavity structure of OTMS allowed the smallest material to create the largest and most stable geometric space, endowing it high HA loading capacity. The modification of pDA on OTMS surface effectively promoted the mineral nucleation of HA in the micro-nano cavities of OTMS. The compression mechanical tests showed that the combination of inorganic HA and organic pDA-OTMS greatly improved the mechanical properties of the construct. Additionally, the HA/pDA-OTMS composite provided adequate 3-D support for osteoblast cell attachment, proliferation and differentiation, as well as significantly up-regulated the expression of osteogenesis-related genes. These results demonstrated that as-prepared HA/pDA-OTMS constructs with combined mechanical strength and excellent osteogenic activity show great application prospects in subchondral bone regeneration.

Processing of Ti50Nb50−xHAx composites by rapid microwave sintering technique for biomedical applications

The main objective of this research is to fabricate porous mechanical-tuned (low elastic modulus and high strength) Ti-based composites with improved bioactivity for orthopaedic applications. Another objective is to demonstrate the potential of microwave sintering and temporary space alloying technique to synthesize porous Ti-based composites. In this study, porous Ti50Nb50−xHAx (x=0, 10 and 20) composite was fabricated for orthopaedic applications using a powder metallurgical and rapid microwave sintering (PM-RMS) process. Effects of key PM-RMS parameters on the structural porosity, compressive strength, and elastic modulus of built composite were then analysed. The microstructure, pore characteristics, and mechanical properties were investigated in detail. Using high hydroxyapatite (HA) content (20%), short sintering time (5min), and high compacting pressure (200MPa) appears to be the best condition among those studied in terms of yielding a high degree of structural porosity (21%) and low elastic modulus (25GPa) in the sintered composite. Since size of pores in the synthesized composite is in the range of 20–30μm, structural porosity not only reduces elastic modulus but also enhances bio-activity of sintered composite. The combination of highly porous structure, low elastic modulus, high compressive strength, improved corrosion resistance, and enhanced bioactivity makes porous Ti-Nb-HA composites fabricated by microwave sintering process potential and promising candidates for orthopedic applications.

Fabrication of C-plane Oriented Hydroxyapatite Film on Amorphous SiO2 Substrate

We investigated a fabrication technique of c-plane oriented hydroxyapatite (HA) crystalline film on low cost amorphous SiO2 substrates to apply the orientation-controlled HA crystal to disposal biochips. An experiment was conducted by the pulsed laser deposition (PLD) method. We showed that a high quality HA crystalline film was able to be grown by using a fluoroapatite (FA) buffer layer, which was self-oriented on amorphous SiO2. A relationship between a FA film thickness and the HA quality was examined with an aim of minimizing a toxic risk of F to biomolecules, even if it was eluted from FA. It was found that the thickness of the FA film could be reduced to about 7.5 nm, at the same time, the crystallinity and a smoothness of HA were also excellent. A crystal growth model of FA on the amorphous SiO2 was also studied. We considered that highly reactive F in a laser-ablated-plume substituted for O on the substrate surface, which became a migration trap, causing 3-dimensional island growth as FA crystal nuclei. This model consistently agreed with a series of experimental results.

Long-term corrosion resistance and fast mineralization behavior of micro-nano hydroxyapatite coated magnesium alloy in vitro

To improve the long-term corrosion resistance of biodegradable AZ31 magnesium alloy, the micro-nano structural hydroxyapatite (HA) coating was fabricated on AZ31 substrate by hydrothermal treatment. The compact and high crystallinity HA coating prepared at 120 °C had excellent electrochemical properties. Moreover, the cell viability experiment revealed that the micro-nano structure coating was conducive to the viability and proliferation of MC3T3-E1 osteoblasts. The immersion experiment in simulated body fluid (SBF) solution showed that the micro-nano structural HA coatings could quickly induce the production of HA mineralization, and then the mineralization evolved into a compact mineralized layer on the surface of coated sample, which provided a long-term protection for the specimen. Even after 147 days of immersion, the coated samples remained the relatively complete macroscopic shape, the corrosion rates were lower than 0.500 mm/y and the pH values of the SBF solution maintained in the range of 7.10–7.80, suggesting when these coated AZ31 magnesium alloys were used as degradable biomaterial implants, they could provide a long-term mechanical support during the healing of damaged bones.

3D Microfluidic Bone Tumor Microenvironment Comprised of Hydroxyapatite/Fibrin Composite.

Bone is one of the most common sites of cancer metastasis, as its fertile microenvironment attracts tumor cells. The unique mechanical properties of bone extracellular matrix (ECM), mainly composed of hydroxyapatite (HA) affect a number of cellular responses in the tumor microenvironment (TME) such as proliferation, migration, viability, and morphology, as well as angiogenic activity, which is related to bone metastasis. In this study, we engineered a bone-mimetic microenvironment to investigate the interactions between the TME and HA using a microfluidic platform designed for culturing tumor cells in 3D bone-mimetic composite of HA and fibrin. We developed a bone metastasis TME model from colorectal cancer (SW620) and gastric cancer (MKN74) cells, which has very poor prognosis but rarely been investigated. The microfluidic platform enabled straightforward formation of 3D TME composed the hydrogel and multiple cell types. This facilitated monitoring of the effect of HA concentration and culture time on the TME. In 3D bone mimicking culture, we found that HA rich microenvironment affects cell viability, proliferation and cancer cell cytoplasmic volume in a manner dependent on the different metastatic cancer cell types and culture duration indicating the spatial heterogeneity (different origin of metastatic cancer) and temporal heterogeneity (growth time of cancer) of TME. We also found that both SW620 and MKN72 cells exhibited significantly reduced migration at higher HA concentration in our platform indicating inhibitory effect of HA in both cancer cells migration. Next, we quantitatively analyzed angiogenic sprouts induced by paracrine factors that secreted by TME and showed paracrine signals from tumor and stromal cell with a high HA concentration resulted in the formation of fewer sprouts. Finally we reconstituted vascularized TME allowing direct interaction between angiogenic sprouts and tumor-stroma microspheroids in a bone-mimicking microenvironment composing a tunable HA/fibrin composite. Our multifarious approach could be applied to drug screening and mechanistic studies of the metastasis, growth, and progression of bone tumors.

Characterization of Mechanical and Micro-Architectural Properties of Porous Hydroxyapatite Bone Scaffold Using Green MicroAlgae as Binder

Novel Hydroxyapatite (HA)-based porous bone scaffold is developed using green microalgae as binding as well as pore-forming agent. The composite scaffolds are developed at 1:2, 2:1 and 1:1 (w/w) compositions of HA and binder, respectively, using solvent-casting technique and their mechanical and micro-architectural properties are investigated. Material characterization of the scaffold shows improved mechanical strength with a maximum compressive strength of 2.89 MPa and maximum interconnected porosity of 65.29%. FT-IR and XRD results confirm formation of crystalline nano-HA in the scaffolds. SEM and TEM micrographs of the scaffolds show pore morphology with a maximum pore diameter of 258 microns and minimum pore diameter of 6 microns and uniformly dispersed rod-shaped nano-HA particles of length 3.95–99.11 nm, respectively. TG/DTG analysis shows high thermal stability of scaffolds with high HA content. Comparative study of the three types of scaffolds shows composites with equal weight ratio of HA, and binder yields the highest porosity and mechanical strength desired for cell growth and support. XRF analysis confirms Ca and P as the major constituent elements of the scaffold. The study highlights the potential of natural biomass as an alternative to synthetic and naturally derived polymeric binders for development of HA-based bone scaffolds.

Development, Characterization and In Vitro Biological Properties of Scaffolds Fabricated From Calcium Phosphate Nanoparticles.

Ceramic materials mimic the mineral composition of native bone and feature osteoconductive properties; they are therefore used to regenerate bone tissue. Much research focuses on increasing the porosity and pore interconnectivity of ceramic scaffolds to increase osteoconductivity, cell migration and cell-cell interaction. We aimed to fabricate biocompatible 3D-scaffolds featuring macro- and microporous calcium phosphates with high pore interconnection. Nanoparticles of hydroxyapatite (HA) and calcium deficient hydroxyapatite (CDHA) were synthesized by wet chemical precipitation. Scaffolds were produced from them by the replication polymeric foam technique. Solid content and sintering temperature were varied. Nanoparticles and scaffolds were characterized regarding morphology, chemical and mineral composition, porosity and mechanical properties. Biocompatibility, cell attachment and distribution were evaluated in vitro with human adipose mesenchymal stem cells. Scaffolds with total porosity of 71%–87%, pores in the range of 280–550 µm and connectivity density up to 43 mm−3 were obtained. Smaller pore sizes were obtained at higher sintering temperature. High solid content resulted in a decrease of total porosity but increased interconnectivity. Scaffolds 50HA/50β-TCP featured superior interconnectivity and mechanical properties. They were bioactive and biocompatible. High HA solid content (40 wt.%) in the HA pure scaffolds was negative for cell viability and proliferation, while in the 50HA/50β-TCP composite scaffolds it resulted more biocompatible.