Modification of hydroxyapatite (HA) powder by carboxymethyl chitosan (CMCS) for 3D printing bioceramic bone scaffolds

The poor mechanical properties of 3D printed HA bone scaffold is always a challenge in tissue engineering, to address this issue, carboxymethyl chitosan (CMCS) was proposed to modify HA bone scaffolds by a physical blending method in this research. A series of HA and HA/CMCS composite ceramic scaffolds were printed by using piezoelectric inkjet 3D printing technology, and their properties were investigated in terms of forming quality, structural morphology, mechanical properties, degradability, cytotoxicity, and cell adhesion growth. The results of forming quality and structural morphology show that with the increase of CMCS content, the forming quality of the samples deteriorated, the pore size and porosity increased. However, when the content of CMCS reached 5 wt%, obvious cracks appeared on the surface of the sample, and the forming quality was relatively poor. The mechanical testing results indicated the toughness of composites could be enhanced by incorporating CMCS into HA, which was attributed to the higher strength connections of the CMCS polymer network between HA particles and the stronger interaction between HA and CMCS molecules. FTIR spectra further revealed the strong hydrogen bonding interaction between CMCS and HA. Moreover, the degradation rate and mineralization ability of the sample increased with the content of CMCS, but the compressive strength during degradation increased with the CMCS content, indicating that incorporating CMCS into HA cannot only improve the mechanical property and biological activity of the scaffold but also makes up the defect of slow degradation of pure HA scaffold. Finally, the cytotoxicity, cell adhesion, and cell proliferation tests show that HA and HA/CMCS composite samples had good cytocompatibility, HA/CMCS sample with 3 wt% CMCS possessed the best bioactivity. In summary, HA/CMCS composite powder with 3 wt% CMCS content is the optimal matrix material for 3D printing bone scaffolds.     

Morphological and thermal characterization of zirconia/hydroxyapatite composites prepared via sol-gel for biomedical applications

The thermal behavior of pure ZrO₂ and hydroxyapatite (denoted as Z and HAp, respectively), as well as three composites with different content of Z and HAp (Z90HAp10, Z70HAp30 and Z50HAp50) prepared via sol-gel method has been studied by thermogravimetry (TG) and first-order derivative of TG up to 1200?°C under inert gas atmosphere. Dehydration, loss of alcohol and acetylacetone and a multi-step thermal decomposition processes has been identified by analyzing the gases evolved in each step by Fourier transform infrared spectroscopy (FTIR). Fresh samples of Z-rich composites undergo an abrupt ejection of material from the crucible around 200?°C with noticeable increase of the sample temperature. During the occurrence of this phenomenon FTIR spectra demonstrated the evolution of gases (CO, CO₂, acetone and ethylene) due to the simultaneous decomposition of acetylacetone and ethanol, not present in the samples calcined at 120?°C. As far as the structural study is concerned, pure Z crystallizes at 1000?°C in the monoclinic system, but the presence of HAp in the composite materials enables the crystallization of Z in the tetragonal phase. Finally, the amorphization degree increases with increasing the content of Z in all the composites treated at 600 and 1000?°C.     

Effects of the doping concentration of boron on physicochemical,mechanical, and biological properties of hydroxyapatite

Ion doping is an approach to modify properties of materials, like hydroxyapatite (HA), that contributes to designing biomaterials with desired characteristics applicable in bone defect treatments. Recently, boron (B) has been noticed in biomaterial fields due to its beneficial effects on formation, growth, and quality of bone. In this study, B-doped HA nanoparticles with different molar concentrations of B (0.05, 0.1, 0.25, and 0.5) were synthesized through microwave-assisted wet precipitation. The effects of B content on various properties of HA were evaluated. The results demonstrated that the size of HA particles reduced from 106 nm to 89-85 nm in B doped materials. Meanwhile, the crystallinity degree of B doped HA (BHA) samples was between 89.90% and 93.77%, compared to 95.19% of HA. Diametral tensile strength of samples was measured in the ranges of 2.51 and 3.61 with no significant difference among groups. The micro-hardness of HA was 0.88 GPa, whilst doped ones had hardness values of 0.5 GPa–0.68 GPa. Biodegradability of samples increased from less than 1% to approximately 4% after 28 days, while B-doping did not make any change in the degradation rate. Doping dosages were appropriate in terms of bioactivity and cell viability, and B doping caused higher bioactivity and cell proliferation. All changed properties were dose-dependent and more effective in doped groups with a higher amount of B. Despite proliferative effect, 260 μg/l and 770 μg/l of B release in two groups with the highest dopant concentrations did not positively influence the osteogenic activity of cells. Our results demonstrated that doping concentrations that resulted in B release ≤260 μg/l seem more appropriate dosage, especially for bone tissue engineering and substitute applications due to promoted bioactivity and proliferation, as well as no obstructive effects on mechanical properties and osteogenic activities of HA.     

Enhanced biosorption of bisphenol A from wastewater using hydroxyapatite elaborated from fish scales and camel bone meal: A RSM@BBD optimization approach

In this work, camel bone biowaste and fish scales were used as a source for the production of hydroxyappatite. Hydroxyapatite (HAP) was extracted from fish scales (FS) and camel bone meal (CBM) using the alkaline heat treatment method. The HAP prepared was analyzed by different characterization techniques such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transformation Infrared spectroscopy (FTIR), Energy Dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) analysis. The HAP developed from FS and CBM biomaterials was used as a highly effective green adsorbent to eliminate bisphenol A (BPA) from water. The pseudo-second-order and Langmuir models were well fitted with the kinetic and adsorption isotherm data, with a maximum adsorption capacity of 74.128 and 89.828 mg/g, respectively for FS and CBM. The BPA adsorption on FS and CBM were optimized by the surface response methodology and the Box Behnken Design (RSM@BBD). The optimal factors were obtained to be for FS (% Removal = 83.51%), an adsorbent dose of 1.375 g/L, C_i of 5 mg/L and contact temp 115.6 min and for CBM (% Removal = 79.38%) were an adsorbent dose of 1.1 g/L, C_i of 6.99 mg/L and contact temp 106.3 min.     

A comprehensive review on the preparation and application of calcium hydroxyapatite: A special focus on atomic doping methods for bone tissue engineering

Hydroxyapatite (HAP) has been considered to be one of the most preferred scaffold materials among many in the last decade for the bone tissue engineering. Be it prosthetic implants, scaffolds or artificial bone cement, hydroxyapatite has received highest attraction among all due to its chemical and physical properties similar to that of human bone. Although it can be used in the bone tissue engineering as the original composition; for enhancing its different properties relevant to in vivo applications, the calcium in HAP may also be replaced by other atomic dopants depending on usage. Here, we review various HAP coating agents and methods, their merits and demerits. We also review various HAP doping materials, including both cationic as well as anionic materials. We discuss the effects and usage of substitution of hydroxyapatite and their subsequent usage in both bone tissue engineering and maxillofacial surgeries. We consider various research articles published in recent times to accomplish detailed discussion on the subject.     

Morphological,mechanical, and biological evolution of pure hydroxyapatite and its composites with titanium carbide for biomedical applications

Pure hydroxyapatite (HAp) was synthesized successfully via a wet chemical precipitation method. To study the influence of TiC (weight % of 5, 10, 15) substitution on the mechanical behavior of pure HAp, its composites with TiC were synthesized using a solid-state reaction method. Herein, detailed investigations of pure HAp and its composites using X-ray powder diffraction (XRD), FTIR spectroscopy, Raman spectroscopy, UV-VIS spectroscopy, SEM followed by EDAX and particle size analysis were carried out. XRD study reveals the phase stability of the prepared HAp and composite samples. However, FTIR and Raman spectroscopic studies revealed the bond formation among the various constituents. Mechanical behavior of HAp, and its composites with TiC were studied using numerous parameters like density, Young's modulus, fracture toughness, and load absorption capability. Based on these studies, it was revealed that the addition of 5 wt % substitution of TiC sintered at 1200 °C significantly enhanced the mechanical properties of pure HAp. Hence, 5 wt % of TiC composite 95HAp-5TiC showed the best mechanical characteristics such as density (2.3060 g/cm³), Young's modulus (14.53 MPa), fracture toughness (19.82 MPa m^1/2), maximum compressive strength (186 MPa) respectively. Cytotoxicity and osteogenic activities of the synthesized pure HAp and its composite, 95HAp-5TiC were performed using osteoblast cells (mouse calvarial) at different concentrations of the samples (0.01 μg, - 100 μg). From the above studies, the cell viability and ALP activities of the composite, 95HAp-5TiC found to be excellent than that of pure HAp. Hence, this composite sample may be utilized for bone implant applications.     

Dnmt3aa but Not Dnmt3ab Is Required for Maintenance of Gametogenesis in Nile Tilapia (Oreochromis niloticus)

Dnmt3a, a de novo methyltransferase, is essential for mammalian germ line DNA methylation. Only one Dnmt3a is identified in mammals, and homozygous mutants of Dnmt3a are lethal, while two Dnmt3a paralogs, dnmt3aa and dnmt3ab, are identified in teleosts due to the third round of genome duplication, and homozygous mutants of dnmt3aa and dnmt3ab are viable in zebrafish. The expression patterns and roles of dnmt3aa and dnmt3ab in gonadal development remain poorly understood in teleosts. In this study, we elucidated the precise expression patterns of dnmt3aa and dnmt3ab in tilapia gonads. Dnmt3aa was highly expressed in oogonia, phase I and II oocytes and granulosa cells in ovaries and spermatogonia and spermatocytes in testes, while dnmt3ab was mainly expressed in ovarian granulosa cells and testicular spermatocytes. The mutation of dnmt3aa and dnmt3ab was achieved by CRISPR/Cas9 in tilapia. Lower gonadosomatic index (GSI), increased apoptosis of oocytes and spermatocytes and significantly reduced sperm quality were observed in dnmt3aa^−/− mutants, while normal gonadal development was observed in dnmt3ab^−/− mutants. Consistently, the expression of apoptotic genes was significantly increased in dnmt3aa^−/− mutants. In addition, the 5-methylcytosine (5-mC) level in dnmt3aa^−/− gonads was decreased significantly, compared with that of dnmt3ab^−/− and wild type (WT) gonads. Taken together, our results suggest that dnmt3aa, not dnmt3ab, plays important roles in maintaining gametogenesis in teleosts.     

Molecular dynamics simulation and experimental study of the bonding properties of polymer binders in 3D powder printed hydroxyapatite bioceramic bone scaffolds

Binder properties are a key factor affecting the quality of bone scaffolds produced using 3D powder printing. In this research, molecular dynamics simulation (MD) and experimental methods were applied to study the cohesive energy density, mechanical properties, bonding behavior, and surface morphology of three polymer binders (PVP, PAM, PVA) employed in the 3D fabrication of hydroxyapatite (HA) bone scaffolds. The bonding mechanisms of the three polymer binders were revealed by analyzing the interaction between the binders and the HA surface. The binding energies between the binders and HA are associated with the cohesive energy density and viscosity of each of the binders, which are attributed to functional groups in the binders. The mechanical properties determined experimentally for the bone scaffolds produced using each of the three polymer binders were in a different relative order than the engineering modulus of the binders and the interaction between the binders and HA calculated in simulations. This is a reflection of the mechanical properties of bone scaffolds being a comprehensive reflection of the basic materials and their bonding effect. Finally, SEM imaging indicated additional factors affecting the mechanical properties and degradation rate of the scaffolds. Conclusions from this work can be used to forecast the properties of three commonly used polymer binders and provide a theoretical basis for the choice of binders in the production of 3DP-fabricated bone scaffolds.     

Synthesis,structural, mechanical,and biological properties of HAp-ZrO2-hBN biocomposites for bone regeneration applications

Nowadays researchers are much interested in bioceramics for their use as biological implants. Researchers have succeeded to derive few bioceramic materials which show good biological response with living tissues. Few of the bioceramics are zirconia, hexagonal boron nitride and hydroxyapatite. Herein, the effects of zirconia nanoparticles and hexagonal boron nitride nanosheets in hydroxyapatite powder on the structural, mechanical, and biological properties were investigated. In this study, the formation of a potential composite with desired mechanical and biological properties is strongly anticipated. The present study is also proposed to provide further faces to improve osteogenic properties of the scaffolding material without altering the established mechanical and biological properties. Three different compositions in the system [(95-x)HAp-x(ZrO₂)-5hBN] (x = 10, 20, 30) were prepared using a simple solid-state reaction technique. In the samples, significant phase was identified for HAp [Calcium Phosphate Hydroxide: Ca₅(PO₄)₃(OH)]. SEM analysis of the composites revealed well-connected and uniform distribution of ZrO₂ and HAp nanoparticles on h-BN sheets. The composite samples 65H30Z5B9h (65HAp-30ZrO₂-5hBN sintered at 900 °C) and 65H30Z5B1T (65HAp-30ZrO₂-5hBN sintered at 1000 °C) showed improved mechanical and tribological behaviors. These samples exhibited excellent mechanical properties like compressive strength, Young's modulus, toughness and density. The obtained values were 2.154 MPa, 0.0182 MPa, 553.82 MJ/m³, 2.29 g/cm³ for 65H30Z5B9h and 3.798 MPa, 0.0832 MPa, 231.59 MJ/m³, 2.31 g/cm³ for 65H30Z5B1T respectively. Cytotoxicity of the composites was studied on Drosophila fly and Mice calvarial osteoblasts cells at five different concentrations. Toxic effect of the composite 65H30Z5B1T on the fly was confirmed by phenotypic observations, trypan blue staining, pupal count, and larval crawling speed. Composite 65H30Z5B1T was found to be toxic in this study, but the composite 65H30Z5B9h was not. Further, cell viability, alkaline phosphates, and mineralization tests confirmed non-toxic property and enhanced osteogenic activities for the composite sample 65H30Z5B9h.     

Evaluation of the electrical and dielectric behavior of the apatite layer formed on the surface of hydroxyapatite/hardystonite/copper oxide hybrid nanocomposites for bone repair applications

The work aimed to prepare nanocomposites with good electrical and mechanical properties and acceptable bioactivity behavior to be suitable for bone repair applications. In this context, hydroxyapatite (HA) and hardystonite (HT) were prepared by mechanochemical synthesis method. Subsequently, nanocomposites of different contents of HA, HT and copper oxide (CuO) were prepared, sintered and characterized by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). In addition, bioactivity was evaluated in vitro after treatment in simulated body fluid (SBF) and HA layer formation was confirmed by SEM in conjunction with energy dispersive X-ray analysis (EDX). The electrical and dielectric properties were measured before and after treatment in SBF solution. Elastic and physical properties were also measured. The results clarified that the sintering temperature used along with the successive increase of HT and CuO contents achieved good densification behavior and better mechanical properties, especially compressive strength, to avoid the stress-shielded bone effect. Also, HT and CuO positively enhanced the electrical conductivity and reduced the dielectric properties of nanocomposites prepared. The latter results have a great role in promoting fracture healing. Based on the above results, the prepared nanocomposites are promising for potential use in bone repair applications.     

The effects of BaTiO3 on the handleability and mechanical strength of the prepared piezoelectric calcium phosphate silicate for bone tissue engineering

Natural bone is a piezoelectric material that can generate electrical signals when subjected to an external force. Although many studies have attempted to develop piezoelectric biomaterials for bone regeneration, post-treatment steps, such as sintering, are always needed. In this study, we prepared an injectable and piezoelectric bone substitute based on nanosized BaTiO₃ (nBT)-added calcium phosphate silicate (CPS). The impacts of nBT on the CPS handleability and mechanical strength were characterized, and show that adding nBT could improve the CPS handleability but affect the CPS mechanical strength in a concentration-dependent manner (from 25.3 ± 1.0 MPa for 10BC to 13.5 ± 1.0 MPa for 40BC). In addition, our approach could fabricate a piezoelectric bone substitute with comparable piezoelectricity to the native bone without any post-treatment. The in vitro analyses demonstrated that nBT/CPS was biocompatible and could promote osteoblast differentiation. In conclusion, our results strongly indicate that the injectable formulation based on nBT/CPS can be a promising candidate in bone tissue engineering, and further research is needed to investigate the biomaterial's performance in bone defect animal models.     

Effect of the temperature and sintering time on the thermal,structural, morphological,and vibrational properties of hydroxyapatite derived from pig bone

This paper focuses in the study of the effect of the temperature and sintering time on structural, morphological, thermal, and vibrational properties of hydroxyapatite obtained from pig bone (BHA). A three-step process was used to get BHA: hydrothermal cleaning, calcination, and cooling. Samples were calcined and cooled inside the furnace under atmosphere air. The samples were calcined at 600 and 1000 °C and sintered at 1, 7, 20, 50 h and studied accordingly. XRD and Raman studies showed an improvement in the crystalline quality as a function of the sintering time, while the samples calcined at 1000 °C did not exhibit structural changes as a function of the sintering time. The presence of magnesium oxide (MgO) was confirmed by XRD and micro EDS analysis as a result of the temperature treatment because this compound was not found in the samples calcined at 600 °C. The crystalline quality of these samples was studied using XRD and Raman spectroscopy.     

Densification behavior and mechanical properties of nano-alumina ceramics prepared by Spark Plasma Sintering with pressure applied at different sintering stages

High densification and fine grain size are the key to achieve excellent mechanical properties of ceramic materials. Pressure-assisted sintering is an effective approach to achieve this goal. However, the pressure at different sintering stages has different effects on the densification behavior of nano-ceramics. In this work, it is found that adjusting the pressure applying regime during Spark Plasma Sintering of nano-alumina ceramics can effectively increase the densification rate and balance the relationship between the densification behaviors of particle coarsening, grain growth and vapor migration. When the pressure is applied at the beginning of the second sintering stage, the high densification and fine grain size microstructures can be both obtained at lower temperatures, leading to the best mechanical properties. This result is of great significance for the preparation of nano-ceramics with excellent mechanical properties.     

Adsorption capacity of bone char for removing fluoride from water solution. Role of hydroxyapatite content,adsorption mechanism and competing anions

The adsorption of fluoride from water on bone char (BC) was investigated in this work, and the fluoride adsorption capacity of BC was compared to that of hydroxyapatite (HAP). The adsorption capacity of BC and HAP drastically increased while decreasing the pH from 7.0 to 5.0. Furthermore, the fluoride adsorption on BC was due to its HAP content and was not considerably affected by the presence of the anions Cl⁻, HCO₃⁻, CO₃²⁻, SO₄²⁻, NO₃⁻ and NO₂⁻. The mechanism of fluoride adsorption on BC was attributed to electrostatic interactions between surface charge of BC and fluoride ions in solution.     

Development and in vivo response of hydroxyapatite/whitlockite from chicken bones as bone substitute using a chitosan membrane for guided bone regeneration

Biomaterials that meet the requirements to stimulate bone tissue formation play a vital role in orthopedics and dentistry. In this work, chitosan and a biphasic, non-cytotoxic material hydroxyapatite/whitlockite were obtained from natural sources, which are available as organic waste. The osteogenic activity was assessed using a rabbit model animal with a chitosan barrier membrane in combination with a bone-filling graft substitute composed of hydroxyapatite/whitlockite. FT-IR results showed the typical absorption bands of the chitosan and hydroxyapatite. Moreover, the X-ray diffraction pattern revealed a typical hexagonal phase of hydroxyapatite and rhombohedral structures related to whitlockite. Masson's trichrome stain showed an early formation of extracellular matrix mineralized, in accord with the surface morphology of a cortical mature bond observed by Scanning Electron Microscopy. The immunocytochemistry results showed a significant increase of positive immunoreactive cells to osteonectin in the treated defects in comparison with the control defects 6 and 8 weeks postoperatively. Overall, the results confirm that the use of this low-cost and versatile biomaterial as a barrier membrane and a bone substitute graft are useful for bone tissue engineering.     

Enhanced mechanical properties and hydrophilic behavior of magnesium oxide added hydroxyapatite nanocomposite: A bone substitute material for load bearing applications

Hydroxyapatite is a multifunctional biomaterial that combines biocompatibility and bioactivity for various biomedical applications such as bone repairing and bioimaging. In the present study nano-hydroxyapatite (n-HAp) was synthesized using microwave irradiation technique. Subsequently, the MgO was introduced into the n-HAp matrix and various bioactive compositions of HAp-MgO nanocomposites were fabricated. The structural, mechanical, in vivo cell viability, and in vivo imaging properties of these nanocomposites were studied. The XRD results show that the composites sintered at 1200 °C, n-HAp partially decomposed into beta-tricalcium phosphate (β-TCP). The sintered density of the composites varying from 2.72 ± 0.066 to 3.03 ± 0.093 g cm⁻³ with the addition of 0.0–2.0 wt % of MgO. As increasing the amounts of MgO, a remarkable increase in the mechanical properties of the composite was achieved. The composite HAp-1.0MgO exhibited the highest mechanical properties with a compressive strength of 111.20 ± 5 MPa, fracture toughness 136.98 ± 5 MJ/m³ and revealed much amplification than pure n-HAp. Thus, the addition of MgO acting as an excellent mechanical reinforcing agent. The surface morphology of the composites revealed a significant change in the porous surface to denser. The low contact angle revealed the considerable hydrophilic nature of the composite surface. The biological study of these nano-composites with Drosophila third instar larvae indicated comparable or more favorable biocompatibility in terms of cell viability. Also internalized by Drosophila third instar larvae exhibited fluorescence under green and red filters using epifluorescence microscopy. Thus, the fabricated HAp-MgO nanocomposites with excellent biological properties are expected to be a multifunctional bioactive material for bone tissue regeneration and cell imaging applications.     

Synthesis, properties and biomedical applications of poly(glycerol sebacate) (PGS): A review

Poly(glycerol sebacate) (PGS) is a biodegradable polymer increasingly used in a variety of biomedical applications. This polyester is prepared by polycondensation of glycerol and sebacic acid. PGS exhibits biocompatibility and biodegradability, both highly relevant properties in biomedical applications. PGS also involves cost effective production with the possibility of up scaling to industrial production. In addition, the mechanical properties and degradation kinetics of PGS can be tailored to match the requirements of intended applications by controlling curing time, curing temperature, reactants concentration and the degree of acrylation in acrylated PGS. Because of the flexible and elastomeric nature of PGS, its biomedical applications have mainly targeted soft tissue replacement and the engineering of soft tissues, such as cardiac muscle, blood, nerve, cartilage and retina. However, applications of PGS are being expanded to include drug delivery, tissue adhesive and hard tissue (i.e., bone) regeneration. The design and fabrication of PGS based devices for applications that mimic native physiological conditions are also being pursued. Novel designs range from accordion-like honeycomb structures for cardiac patches, gecko-like surfaces for tissue adhesives to PGS (nano) fibers for extra cellular matrix (ECM) like constructs; new design avenues are being investigated to meet the ever growing demand for replacement tissues and organs. In less than a decade PGS has become a material of great scrutiny and interest by the biomedical research community. In this review we consolidate the valuable existing knowledge in the fields of synthesis, properties and biomedical applications of PGS and PGS-related biomaterials and devices.