Microwave-assisted preparation of Nano-hydroxyapatite for bone substitutes

Radiological properties of nano-hydroxyapatite compared to natural equine hydroxyapatite quantified using dual-energy CT and high-field MR

In equine medicine, assisted bone regeneration, including use of biomaterial substitutes like hydroxyapatite (HAP), is crucial for addressing bone defects. To follow-up on the outcome of HAP-based bone defect treatment, the advancement in quantified diagnostic imaging protocols is needed. This study aimed to quantify and compare the radiological properties of the HAP graft and natural equine bone using Magnetic Resonance (MR) and Computed Tomography (CT), both Single (SECT) and Dual Energy (DECT). SECT and DECT, allow for the differentiation of three HAP grain sizes, by progressive increase in relative density (RD). SECT, DECT, and MR enable the differentiation between natural cortical bone and synthetic HAP graft by augmentation in Effective Z and material density (MD) in HAP/Water, Calcium/Water, and Water/Calcium reconstructions, alongside the reduction in T2 relaxation time. The proposed quantification provided valuable radiological insights into the composition of HAP grafts, which may be useful in follow-up bone defect treatment.

Correlation between Ca Release and Osteoconduction by 3D-Printed Hydroxyapatite-Based Templates

The application of hydroxyapatite (HA)-based templates is quite often seen in bone tissue engineering since that HA is an osteoconductive bioceramic material, which mimics the inorganic component of mineralized tissues. However, the reported osteoconductivity varies in vitro and in vivo, and the levels of calcium (Ca) release most favorable to osteoconduction have yet to be determined. In this study, HA-based templates were fabricated by melt-extrusion 3D-printing and characterized in order to determine a possible correlation between Ca release and osteoconduction. The HA-based templates were blended with poly(lactide-co-trimethylene carbonate) (PLATMC) at three different HA ratios: 10, 30, and 50%. The printability and physical properties of the HA templates were compared with those of pristine PLATMC. In vitro, osteoconductivity was assessed using seeded human bone marrow-derived mesenchymal stem cells. A mild rate of Ca release was observed for HA10 templates, which exhibited higher mineralized extracellular matrix (ECM) secretion than PLATMC at 14 and 21 days. In contrast, the high rate of Ca release exhibited by HA30 and HA50 templates was associated with reduced osteoconduction and impeded mineralized ECM secretion in vitro. Similar results were observed in vivo. In the calvarial defect model in rabbit, PLATMC and HA10 templates exhibited the highest amount of new bone formation, with obvious contact osteogenesis on their surfaces. In contrast, HA30 and HA50 exhibited distant osteogenesis and reduced amounts of new bone ingrowth. It is concluded that HA-based templates are osteoconductive only at low rates of Ca release.

Calcium extraction from catfish bone powder optimized by response surface methodology for inducing alginate bead

Catfish bone powder (CBP), prepared from catfish head, was a good source of natural minerals, particularly calcium (Ca) and phosphorous (P). The Ca content were higher than P when analyzed by either chemical or SEM in EDS mode. These elements were found in the crystal form of hydroxyapatite (HA) complex with protein, as assessed by spectroscopic techniques, including XRD and FT-IR. Thus, low Ca solubility was thus observed at 0.03 ± 0.0038 % and digestion of complex HA is required for more liberation of Ca. Citric acid was therefore applied for Ca extraction using a microwave-assisted method. The conditions were optimized using response surface methodology with central composite design to evaluate the effect of extraction time, microwave power, citric acid concentration, and CBP weight. Based on a linear prediction model, the optimum condition to extract Ca from 0.4 g of CBP was at 0.1 M citric acid using microwave power of 275 W for 60 s. This condition provided a Ca content of 1.11 mg/mL in solution, which extract calcium about 27.75 % from original CBP weight. This Ca concentration was enough to induce alginate drops (1.0 %) to form hydro-beads, indicating its functional property in food system. These results provided the promising method to extract natural calcium from fishery by-products for further creating innovative food products.

Sustainable and Environmentally Friendly Microwave Synthesis of Nano-Hydroxyapatite from Decarbonized Eggshells

The sustainable microwave (MW) synthesis of hydroxyapatite (HAp) from decarbonized eggshells was investigated. Decarbonization of eggshells, as a natural source of calcium carbonate (CaCO3), was carried out in the current study at ambient conditions to reduce the footprint of CO2 emissions on our environment where either calcination or acidic direct treatments of eggshells produce CO2 emissions, which is a major cause for global warming. Eggshell decarbonization was carried out via the chemical reaction with sodium hydroxide (NaOH) alkaline solution in order to convert eggshell waste into calcium hydroxide (Ca(OH)2) and simultaneously store CO2 as a sodium carbonate (Na2CO3) by-product which is an essential material in many industrial sectors. The produced Ca(OH)2 was mixed with ammonium dihydrogen phosphate (NH4H2PO4) reagent at pH~11 before being subjected to MW irradiation at 2.45 GHz frequency for 5 min using 800 Watts to prepare HAp. The prepared Nano-HAp was characterized using X-ray diffraction (XRD) where the crystal size was ~28 nm using the Scherrer equation. The elongated rod-like nano-HAp crystals were characterized using scanning electron microscopy (SEM) equipped with dispersive energy X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). MW synthesis of decarbonized eggshells is considered as a sustainable and environmentally friendly route to produce promising bioceramics such as nano-HAp. Concurrently, decarbonization of eggshells offers the ability to store CO2 as a high value-added Na2CO3 material.

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

Characterization and in vitro bioactivity evaluation of polyvinyl alcohol incorporated electro spun chitosan/ fluor apatite nanofibrous scaffold for bone tissue engineering

In this study, polyvinyl alcohol/chitosan/fluor apatite scaffolds with different concentrations of polyvinyl alcohol of 0.075 g ml-1 and 0.1 g ml-1, respectively named A and B fabricated by electrospinning method to use in tissue engineering. By examining the scaffolds by FE-SEM, an appetite layer formation which was on the scaffold surface was clearly observable. Increasing the concentration of polyvinyl alcohol from 0.075 g ml-1 to 0.1 g ml-1 in the nanofibrous scaffolds improved degradation characteristic with an optimized value of 26 ± 2 and 42 ± 1 % after 28 days, respectively. The mean diameter of fibers both scaffolds was 405 nm and 212 nm, respectively. Furthermore, the percentage of porosity in both scaffolds was calculated as 84% and 91%, separately. The level of hydrophilicity of the scaffolds was measured by the dynamic contact angle method. Moreover, the increase in the percentage of polyvinyl alcohol led to the decrease in the average contact angle in scaffold A and scaffold B from 90° to 70°, respectively. The results of bone marrow culture test with MG-63 (NCBI C555) cell on the surface of scaffolds demonstrated not cytotoxicity in the resulting scaffolds as well as a suitable substrate for the adhesion and growth of the cells. According to our findings, the electrospun fluorapatite-incorporated-chitosan/polyvinyl alcohol scaffold could provide a new nanocomposite for biomedical applications.

Biological analyses of the effects of TiO2 and PEG-b-PLA nanoparticles on three-dimensional spheroid-based tumor

The aim of our study was to monitor the antiproliferative/ cytotoxic and genotoxic effects of both, poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) and titanium dioxide (TiO2) nanoparticles on the tumor (HT-29, MCF-7, U118MG) and healthy (HEK-293T) cell lines during 2D cultivation and during cultivation in the spheroid form (3D cultivation). Cells or spheroids were cultivated with nanoparticles (0.01, 0.1, 1, 10, 50, and 100 ?g/ml) for 72 hours. The cytotoxic effect was determined by the MTT test and the genotoxic effect by the comet assay. We found that 2D cultivation of tumor cell lines with PEG-b-PLA and TiO2 nanoparticles had an anti-proliferative effect on human colon cancer cell line HT-29, human breast cancer cell line MCF-7, human glioma cell line U-118MG during 72h cultivation, but not on control/healthy HEK-293T cells. At the concentrations used, the tested nanoparticles caused no cytotoxic effect on tumor cell lines. Nanoparticles PEG-b-PLA induced significant damage to DNA in HT-29 and MCF-7 cells, while TiO2 nanoparticles in MCF-7 and U-118MG cells. Only PEG-b-PLA nanoparticles caused cytotoxic (IC50 = 7 mikrog/ml) and genotoxic effects on the healthy cell line HEK-293T after 72h cultivation. The cells which were cultivated in spheroid forms were more sensitive to both types of nanoparticles. After 72h cultivation, we observed the cytotoxic effect on both, the tumor and healthy cell lines.

Design Strategies for Hydroxyapatite-Based Materials to Enhance Their Catalytic Performance and Applicability

Hydroxyapatite (HAP) is a green catalyst that has a wide range of applications in catalysis due to its high flexibility and multifunctionality. These properties allow HAP to accommodate a large number of catalyst modifications that can selectively improve the catalytic performance in target reactions. To date, many studies have been conducted to elucidate the effect of HAP modification on the catalytic activities for various reactions. However, systematic design strategies for HAP catalysts are not established yet due to an incomplete understanding of underlying structure-activity relationships. In this review, tuning methods of HAP for improving the catalytic performance are discussed: 1) ionic composition change, 2) morphology control, 3) incorporation of other metal species, and 4) catalytic support engineering. Detailed mechanisms and effects of structural modulations on the catalytic performances for attaining the design insights of HAP catalysts are investigated. In addition, computational studies to understand catalytic reactions on HAP materials are also introduced. Finally, important areas for future research are highlighted.

Surface functionalized nanoparticles: A boon to biomedical science

The rapid development of nanomedicine has increased the likelihood that manufactured nanoparticles will one day come into contact with people and the environment. A variety of academic fields, including engineering and the health sciences, have taken a keen interest in the development of nanotechnology. Any significant development in nanomaterial-based applications would depend on the production of functionalized nanoparticles, which are believed to have the potential to be used in fields like pharmaceutical and biomedical sciences. The functionalization of nanoparticles with particular recognition chemical moieties does result in multifunctional nanoparticles with greater efficacy while at the same time minimising adverse effects, according to early clinical studies. This is because of traits like aggressive cellular uptake and focused localization in tumours. To advance this field of inquiry, chemical procedures must be developed that reliably attach chemical moieties to nanoparticles. The structure-function relationship of these functionalized nanoparticles has been extensively studied as a result of the discovery of several chemical processes for the synthesis of functionalized nanoparticles specifically for drug delivery, cancer therapy, diagnostics, tissue engineering, and molecular biology. Because of the growing understanding of how to functionalize nanoparticles and the continued work of innovative scientists to expand this technology, it is anticipated that functionalized nanoparticles will play an important role in the aforementioned domains. As a result, the goal of this study is to familiarise readers with nanoparticles, to explain functionalization techniques that have already been developed, and to examine potential applications for nanoparticles in the biomedical sciences. This review's information is essential for the safe and broad use of functionalized nanoparticles, particularly in the biomedical sector.

Hydroxyapatite-based composites: Excellent materials for environmental remediation and biomedical applications

Given their unique characteristics and properties, Hydroxyapatite (HAp) nanomaterials and nanocomposites have been used in diverse advanced catalytic technologies and in the field of biomedicine, such as drug and protein carriers. This paper examines the structure and properties of the manufactured HAp as well as a variety of synthesis methods, including hydrothermal, microwave-assisted, co-precipitation, sol-gel, and solid-state approaches. Additionally, the benefits and drawbacks of various synthesis techniques and ways to get around them to spur more research are also covered. This literature discusses the various applications, including photocatalytic degradation, adsorptions, and protein and drug carriers. The photocatalytic activity is mainly focused on single-phase, doped-phase, and multi-phase HAp, while the adsorption of dyes, heavy metals, and emerging pollutants by HAp are discussed in the manuscript. Furthermore, the use of HAp in treating bone disorders, drug carriers, and protein carriers is also conferred. In light of this, the development of HAp-based nanocomposites will inspire the next generation of chemists to improve upon and create stable nanoparticles and nanocomposites capable of successfully addressing major environmental concerns. This overview's conclusion offers potential directions for future study into HAp synthesis and its numerous applications.

Estradiol and zinc-doped nano hydroxyapatite as therapeutic agents in the prevention of osteoporosis; oxidative stress status, inflammation, bone turnover, bone mineral density, and histological alterations in ovariectomized rats

Osteoporosis (OP) is a serious health problem, and the most popular therapeutic strategy for OP is hormone replacement (estrogen); however, it increases the risk of reproductive cancers. Hydroxyapatite (HA) nanoparticles have a similar chemical structure to the bone mineral component and can be used as a new remedy for OP. This study was designed to investigate the osteoporosis-protective potential of nano zinc hydroxyapatite (ZnHA-NPs) and/or estradiol (E2) combined therapy. A total of 35 adult female rats were assigned into five groups (n = 7): 1) control group; 2) ovariectomized group (OVX); 3) OVX received oral estradiol replacement therapy (OVX/E2); 4) OVX received ZnHA replacement therapy (OVX/ZnHA); and 5) OVX received both estradiol and ZnHA-NPs combined therapy (OVX/E2+ZnHA). After 3 months of treatment, serum bone markers and estrogen level, oxidative/antioxidant, and inflammatory cytokines were determined. Additionally, femoral expression of estrogen receptors alpha and beta (ESR1; ESR2), receptor activator of nuclear factor-kappa B (RANKL) ligand, osteoprotegerin (OPG), bone mineral density (BMD), histological alterations, and immunohistochemical expression of vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) were assessed. ALP, PINP, Ca, and P concentrations improved significantly (p < 0.05) in all treatment groups, especially in the OVX/E + ZnHA group. MDA and NO were higher in OVX rats, while SOD activity and GSH were lower (p < 0.05). E2 alone or with ZnHA-NPs restored the estimated antioxidant molecules and cytokines toward normal levels in OVX rats (p < 0.05). On the other hand, E2 and ZnHA increased OPG and OC expression in femurs while decreasing ESR1, ESR2, and NF-kB expression (p < 0.05). The combination treatment was superior in the restoration of normal femoral histoarchitecture and both cortical and trabecular BMD (p < 0.05). Overall, the combined therapy of OVX/E2+ZnHA was more effective than the individual treatments in attenuating excessive bone turnover and preventing osteoporosis.

Alkali Niobate Powder Synthesis Using an Emerging Microwave-Assisted Hydrothermal Method

For more than five decades, alkali niobate-based materials (K_xNa_1-xNbO₃) have been one of the most promising lead-free piezoelectric materials researched to be used in electronics, photocatalysis, energy storage/conversion and medical applications, due to their important health and environmentally friendly nature. In this paper, our strategy was to synthetize the nearest reproductible composition to K_xNa_1-xNbO₃ (KNN) with x = 0.5, placed at the limit of the morphotropic phase boundary (MPB) with the presence of both polymorphic phases, orthorhombic and tetragonal. The wet synthesis route was chosen to make the mix crystal powders, starting with the suspension preparation of Nb₂O₅ powder and KOH and NaOH alkaline solutions. Hydrothermal microwave-assisted maturation (HTMW), following the parameter variation T = 200-250 °C, p = 47-60 bar and dwelling time of 30-90 min, was performed. All powders therefore synthesized were entirely K_xN_1-xNbO₃ solid solutions with x = 0.06-0.69, and the compositional, elemental, structural and morphological characterization highlighted polycrystalline particle assemblage with cubic and prismatic morphology, with sizes between 0.28 nm and 2.95 μm and polymorphic O-T phase coexistence, and a d₃₃ piezoelectric constant under 1 pC/N of the compacted unsintered and unpoled discs were found.

The Synthesis of Hydroxyapatite by Hydrothermal Process with Calcium Lactate Pentahydrate: The Effect of Reagent Concentrations, pH, Temperature, and Pressure

Hydroxyapatite and other calcium phosphates in the form of whiskers are lately widely considered as fillers for biocomposites due to their special biological and reinforcing properties. Depending on the method of synthesis, apatite whiskers of various sizes and phase composition can be obtained. In our work, hydroxyapatite (HAp) whiskers were successfully prepared in reaction between calcium lactate pentahydrate and orthophosphoric acid. The advantage of the proposed technique is the simple but precise control of the HAp crystal morphology and high product purity which is necessary for biomedical applications. The effect of reagent concentrations, pH, reaction temperature, and pressure on HAp whiskers' morphology and composition was investigated. In the result, we obtained hydroxyapatite of different morphology such as whiskers, hexagonal rods, and nanorods. The products were characterized by SEM, XRD, and FTIR. In this work, the synthesis of HAp whiskers by direct decomposition of calcium lactate pentahydrate chelates under hydrothermal conditions was showed for the first time.

G, Adhikari R. Isolation of Antibacterial Nano-Hydroxyapatite Biomaterial from Waste Buffalo Bone and Its Characterization

Hydroxyapatite nanoparticles were isolated from a biowaste, buffalo bone, via the thermal decomposition method. The resulting white powdered material was characterized by Fourier Transformed Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) analysis. The FTIR spectra confirmed that a heat treatment of the bone powder at the temperature at or above 1223 K removed the organic moieties leading to the formation of a pure inorganic biomineral. The XRD analyses showed that the obtained material was nanocrystalline HAp (nano-HAp) with an average grain diameter of 25 nm, while their rod-shaped particles with their tightly agglomerated morphology were confirmed by the SEM analysis. Besides Calcium (Ca), Phosphorous (P), and Oxygen (O), trace amounts of Aluminum (Al), Magnesium (Mg), Copper (Cu), Zirconium (Zr) and Carbon (C) were also found by EDX analysis. Antibacterial activity of nano-HAp against six standard isolates was investigated by the agar well diffusion method and found to be more susceptible to Acinetobacter baumannii while other standard strains such as Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus showed lesser susceptibility and no antibacterial activity was noticed against Salmonella typhi and Methicillin resistant Staphylococcus aureus (MRSA) with the analysed concentration of nano-HAp suggesting its potential application in biomedical fields.

Microfluidic encapsulation for controlled release and its potential for nanofertilisers

Nanotechnology is increasingly being utilized to create advanced materials with improved or new functional attributes. Converting fertilizers into a nanoparticle-form has been shown to improve their efficacy but the current procedures used to fabricate nanofertilisers often have poor reproducibility and flexibility. Microfluidic systems, on the other hand, have advantages over traditional nanoparticle fabrication methods in terms of energy and materials consumption, versatility, and controllability. The increased controllability can result in the formation of nanoparticles with precise and complex morphologies (e.g., tuneable sizes, low polydispersity, and multi-core structures). As a result, their functional performance can be tailored to specific applications. This paper reviews the principles, formation, and applications of nano-enabled delivery systems fabricated using microfluidic approaches for the encapsulation, protection, and release of fertilizers. Controlled release can be achieved using two main routes: (i) nutrients adsorbed on nanosupports and (ii) nutrients encapsulated inside nanostructures. We aim to highlight the opportunities for preparing a new generation of highly versatile nanofertilisers using microfluidic systems. We will explore several main characteristics of microfluidically prepared nanofertilisers, including droplet formation, shell fine-tuning, adsorbate fine-tuning, and sustained/triggered release behavior.

Marine-Derived Biowaste Conversion into Bioceramic Membrane Materials: Contrasting of Hydroxyapatite Synthesis Methods

Marine-derived biowaste increment is enormous, yet could be converted into valuable biomaterial, e.g., hydroxyapatite-based bioceramic. Bioceramic material possesses superiority in terms of thermal, chemical, and mechanical properties. Bioceramic material also has a high level of biocompatibility when projected into biological tissues. Tuning the porosity of bioceramic material could also provide benefits for bioseparation application, i.e., ultrafiltration ceramic membrane filtration for food and dairy separation processes. This work presents the investigation of hydroxyapatite conversion from crab-shells marine-based biowaste, by comparing three different methods, i.e., microwave, coprecipitation, and sol-gel. The dried crab-shells were milled and calcinated as calcium precursor, then synthesized into hydroxyapatite with the addition of phosphates precursors via microwave, coprecipitation, or sol-gel. The compound and elemental analysis, degree of crystallinity, and particle shape were compared. The chemical compounds and elements from three different methods were similar, yet the degree of crystallinity was different. Higher Ca/P ratio offer benefit in producing a bioceramic ultrafiltration membrane, due to low sintering temperature. The hydroxyapatite from coprecipitation and sol-gel methods showed a significant degree of crystallinity compared with that of the microwave route. However, due to the presence of Fe and Sr impurities, the secondary phase of Ca9FeH(PO4)7 was found in the sol-gel method. The secondary phase compound has high absorbance capacity, an advantage for bioceramic ultrafiltration membranes. Furthermore, the sol-gel method could produce a snake-like shape, compared to the oval shape of the coprecipitation route, another benefit to fabricate porous bioceramic for a membrane filter.

A review on the synthesis and properties of hydroxyapatite for biomedical applications

Hydroxyapatite (HA or HAp) is one of the most preferred biomaterials, specifically for bone tissue engineering. HAp is available naturally and is also chemically synthesized. The properties, shape, size and crystalline structure and applications of HAp vary widely depending on the source and extraction methods used. In addition to conventional chemical approaches such as precipitation or sol-gel techniques, newer methods such as microwave synthesis and atomic-layer deposition provide an opportunity to generate HAp with desirable structure and properties. Various methods used for the synthesis of HAp have their own pros and cons. Hence, it is essential to understand the role of specific methods and conditions on the properties and structure of HAps in order to obtain HAp with properties suitable for specific applications. In addition to pure HAp, substantial efforts have been made to dope HAp with various minerals or bioentities to enhance their suitability for medical, environmental remediation and other approaches. In this review, we provide an overview of the various chemical methods used to produce HAp, properties of the HAp produced and its potential applications. Particular focus of this paper is on the co-relation between properties and processes used to synthesis HAp. This review will enable readers to quickly understand the importance of synthesis methods and conditions on the properties of HAp and choose appropriate means to generate HAp with desired properties for specific applications.

Nano-Hydroxyapatite vs. Xenografts: Synthesis, Characterization, and In Vitro Behavior

This research focused on the synthesis of apatite, starting from a natural biogenic calcium source (egg-shells) and its chemical and morpho-structural characterization in comparison with two commercial xenografts used as a bone substitute in dentistry. The synthesis route for the hydroxyapatite powder was the microwave-assisted hydrothermal technique, starting from annealed egg-shells as the precursor for lime and di-base ammonium phosphate as the phosphate precursor. The powders were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), X-ray fluorescence spectroscopy (XRF), and cytotoxicity assay in contact with amniotic fluid stem cell (AFSC) cultures. Compositional and structural similarities or differences between the powder synthesized from egg-shells (HA1) and the two commercial xenograft powders-Bio-Oss®, totally deproteinized cortical bovine bone, and Gen-Os®, partially deproteinized porcine bone-were revealed. The HA1 specimen presented a single mineral phase as polycrystalline apatite with a high crystallinity (Xc 0.92), a crystallite size of 43.73 nm, preferential growth under the c axes (002) direction, where it mineralizes in bone, a nano-rod particle morphology, and average lengths up to 77.29 nm and diameters up to 21.74 nm. The surface of the HA1 nanoparticles and internal mesopores (mean size of 3.3 ± 1.6 nm), acquired from high-pressure hydrothermal maturation, along with the precursor's nature, could be responsible for the improved biocompatibility, biomolecule adhesion, and osteoconductive abilities in bone substitute applications. The cytotoxicity assay showed a better AFSC cell viability for HA1 powder than the commercial xenografts did, similar oxidative stress to the control sample, and improved results compared with Gen-Os. The presented preliminary biocompatibility results are promising for bone tissue regeneration applications of HA1, and the study will continue with further tests on osteoblast differentiation and mineralization.

New Prospects in Nano Phased Co-substituted Hydroxyapatite Enrolled in Polymeric Nanofiber Mats for Bone Tissue Engineering Applications

The most common forms of tissue impairment are fracture bones and significant bone disorders caused by multiple traumas or normal aging. Surgical care sometimes necessitates the placement of a temporary or permanent prosthesis, which continues to be a challenge for orthopedic surgeons, including those with large bone defects. Electrospun scaffolds made from natural and synthetic nanofiber-based polymers are studied as natural extracellular matrix (ECM)-like scaffolds for tissue engineering. Besides, nanostructured materials have properties and functions depending on the scale of natural materials such as hydroxyapatite (HAP), ranging from 1 to 100 nm, which activity was proficient upon enrolled in nanofiber mats. The use of nanofibers in combination with nano-HAP has increased the scaffold's ability to replicate the construction of natural bone tissue that is the aim of the present text. In bone engineering, nanofiber substrates facilitate cell adhesion, proliferation, and differentiation, while HAP induces cells to secrete ECM for bone mineralization and development. This review aims to draw the reader's attention to the critical issues with synthetic and natural polymers containing HAP in bone tissue engineering; co-substituted hydroxyapatite has also been mentioned.

The Physico-Chemical Properties and Exploratory Real-Time Cell Analysis of Hydroxyapatite Nanopowders Substituted with Ce, Mg, Sr, and Zn (0.5-5 at.%)

Cation-substituted hydroxyapatite (HA), standalone or as a composite (blended with polymers or metals), is currently regarded as a noteworthy candidate material for bone repair/regeneration either in the form of powders, porous scaffolds or coatings for endo-osseous dental and orthopaedic implants. As a response to the numerous contradictions reported in literature, this work presents, in one study, the physico-chemical properties and the cytocompatibility response of single cation-doped (Ce, Mg, Sr or Zn) HA nanopowders in a wide concentration range (0.5–5 at.%). The modification of composition, morphology, and structure was multiparametrically monitored via energy dispersive X-ray, X-ray photoelectron, Fourier-transform infrared and micro-Raman spectroscopy methods, as well as by transmission electron microscopy and X-ray diffraction. From a compositional point of view, Ce and Sr were well-incorporated in HA, while slight and pronounced deviations were observed for Mg and Zn, respectively. The change of the lattice parameters, crystallite size, and substituting cation occupation factors either in the Ca(I) or Ca(II) sites were further determined. Sr produced the most important HA structural changes. The in vitro biological performance was evaluated by the (i) determination of leached therapeutic cations (by inductively coupled plasma mass spectrometry) and (ii) assessment of cell behaviour by both conventional assays (e.g., proliferation—3-(4,5-dimethyl thiazol-2-yl) 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay; cytotoxicity—lactate dehydrogenase release assay) and, for the first time, real-time cell analysis (RTCA). Three cell lines were employed: fibroblast, osteoblast, and endothelial. When monophasic, the substituted HA supported the cells’ viability and proliferation without signs of toxicity. The RTCA results indicate the excellent adherence of cells. The study strived to offer a perspective on the behaviour of Ce-, Mg-, Sr-, or Zn-substituted HAs and to deliver a well-encompassing viewpoint on their effects. This can be highly important for the future development of such bioceramics, paving the road toward the identification of candidates with highly promising therapeutic effects.

Nanotechnology in cosmetics pros and cons

The field of nanotechnology is being greatly explored by cosmetic industries in order to improve the efficacy of cosmetic products. The increased use of nanomaterials in the field of cosmetics can have two sides as health-related benefits and detrimental effects. This review mainly seeks the pros and cons of the use of nanomaterials in cosmetics along with some examples of nanomaterials that are widely used in cosmetic industries along with different types of nanotechnology-based cosmetic products. The benefits of nanomaterials in cosmetic formulations are huge. Moreover the study regarding the toxic effects on the health also equally matters. This review gives a brief outline of the advantages as well as disadvantages of nanotechnology in cosmetics.

Quenching of the Eu3+ Luminescence by Cu2+ Ions in the Nanosized Hydroxyapatite Designed for Future Bio-Detection

The hydroxyapatite nanopowders of the Eu3+-doped, Cu2+-doped, and Eu3+/Cu2+-co-doped Ca10(PO4)6(OH)2 were prepared by a microwave-assisted hydrothermal method. The structural and morphological properties of the products were investigated by X-ray powder diffraction (XRD), transmission electron microscopy techniques (TEM), and infrared spectroscopy (FT-IR). The average crystal size and the unit cell parameters were calculated by a Rietveld refinement tool. The absorption, emission excitation, emission, and luminescence decay time were recorded and studied in detail. The 5D0 → 7F2 transition is the most intense transition. The Eu3+ ions occupied two independent crystallographic sites in these materials exhibited in emission spectra: one Ca(1) site with C3 symmetry and one Ca(2) sites with Cs symmetry. The Eu3+ emission is strongly quenched by Cu2+ ions, and the luminescence decay time is much shorter in the case of Eu3+/Cu2+ co-doped materials than in Eu3+-doped materials. The luminescence quenching mechanism as well as the schematic energy level diagram showing the Eu3+ emission quenching mechanism using Cu2+ ions are proposed. The electron paramagnetic resonance (EPR) technique revealed the existence of at least two different coordination environments for copper(II) ion.

Multifunctional Hydroxyapatite/Silver Nanoparticles/Cotton Gauze for Antimicrobial and Biomedical Applications

Medical textiles have played an increasingly important protection role in the healthcare industry. This study was aimed at improving the conventional cotton gauze for achieving advanced biomedical specifications (coloration, UV-protection, anti-inflammation, and antimicrobial activities). These features were obtained by modifying the cotton gauze fabrics via in-situ precipitation of hydroxyapatite nanoparticles (HAp NP), followed by in-situ photosynthesis of silver (Ag) NPs with ginger oil as a green reductant with anti-inflammation properties. The HAp-Ag NPs coating provides good UV-protection properties. To further improve the HAp and Ag NPs dispersion and adhesion on the surface, the cotton gauze fabrics were modified by cationization with chitosan, or by partial carboxymethylation (anionic modification). The influence of the cationic and anionic modifications and HAp and Ag NPs deposition on the cotton gauze properties (coloration, UV-protection, antimicrobial activities, and water absorption) was thoroughly assessed. Overall, the results indicate that chemical (anionic and cationic) modification of the cotton gauze enhances HAp and Ag NPs deposition. Chitosan can increase biocompatibility and promotes wound healing properties of cotton gauze. Ag NP deposition onto cotton gauze fabrics brought high antimicrobial activities against Candida albicans, Gram-positive and Gram-negative bacteria, and improved UV protection.

UV-assisted synthesis of hydroxyapatite from eggshells at ambient temperature: cytotoxicity, drug delivery and bioactivity

Hydroxyapatite [Ca10(PO4)6(OH)2], an important biomaterial, retains a chemical structure that is similar to the mineral phase of bone. Consequently, the ability of hydroxyapatite (Hap) to augment bone growth within bone tissue has made it a potential candidate for use as a hard tissue-implant material. In this work, adopting a UV-mediated solid-state method for the first time, hydroxyapatite was synthesized from eggshells and no thermal treatment was used but ambient temperature was maintained. This simple synthesis process involved a combination of ball milling of the starting materials followed by UV-irradiation. UV-excitation of the Ca and P precursors resulted in the desired Hap and X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopic techniques were used for characterization. The potency of UV-Hap as a biomaterial was examined via the bioactivity, cytotoxicity and the drug (ciprofloxacin) loading-releasing response, which was encouraging. The results of the cell viability assays complied an insignificant cytotoxicity and the simulated body fluid immersion test indicated the bioactivity was within the acceptable range. On the other hand, to better understanding the drug ejection and associated transport phenomenon, two kinetic models (Higuchi and Ritger-Peppas models) were used and a diffusion controlled ciprofloxacin release mechanism was observed using the Higuchi model. However, the experimental outcomes of a drug delivery response exposed UV-Hap as a favorable vehicle for drug loading and release. Hence, this research highlights the prospects of a UV-assisted synthesis method as a green route for the synthesis of Hap to be applied in biomedical fields.

Recent Achievements and Future Challenges in Nanoscience and Nanotechnology

The article presents the investigation results of the formation and synthesis of nanosized materials which were obtained at the Institute of Combustion Problems, many works have been brought to practical use. Investigations of low-temperature soot formation become the basis of nanomaterial synthesis methods, developed at the Institute for Combustion Problems since 1985. Flame can be considered as a chemical reactor to produce target products. The main feature of the processes based on technological combustion is that the target product is formed as a result of the combustion reaction, occurring spontaneously at high temperatures with a high speed without consuming external energy, i.e. due to its own heat. With the development of nanotechnology, new challenges have emerged in the synthesis of nanomaterials under combustion synthesis conditions. Below is a list of works on nanomaterials synthesis carried out at the Institute: complete scheme of soot formation; energy intensive nanocarbon materials; development and study of perovskite photocatalysts for hydrogen evolution; obtaining carbon fibers by the method of electrospinning; obtaining of biologically soluble membranes based on polymeric nanofibres and hydroxyapatite of calcium; synthesis of nanocarbon sorbents for purification of water from heavy metal ions.

Microwave-Assisted Fabrication of Mesoporous Silica-Calcium Phosphate Composites for Dental Application

Herein, the microwave-assisted wet precipitation method was used to obtain materials consisting of mesoporous silica (SBA-15) and calcium orthophosphates (CaP). Composites were prepared through immersion of mesoporous silica in different calcification coating solutions and then exposed to microwave radiation. The composites were characterized in terms of molecular structure, crystallinity, morphology, chemical composition, and mineralization potential by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). The application of microwave irradiation resulted in the formation of different types of calcium orthophosphates such as calcium deficient hydroxyapatite (CDHA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP) on the SBA-15 surface, depending on the type of coating solution. The composites for which the progressive formation of hydroxyapatite during incubation in simulated body fluid was observed were further used in the production of final pharmaceutical forms: membranes, granules, and pellets. All of the obtained pharmaceutical forms preserved mineralization properties.

Tunable Microstructure and Morphology of the Self-Assembly Hydroxyapatite Coatings on ZK60 Magnesium Alloy Substrates Using Hydrothermal Methods

Hydroxyapatite coatings have been widely used to improve the corrosion resistance of biodegradable magnesium alloys. In this paper, in order to manufacture the ideal hydroxyapatite (HA) coating on the ZK60 magnesium substrate by hydrothermal method, formation mechanism of enhanced hydroxyapatite (HA) coatings, influence of pH values of the precursor solution on the HA morphology, corrosion resistance and cytotoxicity of HA coatings have been investigated. Results show that the growth pattern of the HA is influenced by the local pH value. HA has a preferential c-axis and higher crystallinity in the alkaline environment developing a nanorod-like structure, while in acid and neutral environments it has a preferential growth along the a(b)-plane with a lower crystallinity, developing a nanosheet-like structure. The different morphology and microstructure lead to different degradation behavior and performance of HA coatings. Immersion and electrochemical tests show that the neutral environment promote formation of HA coatings with high corrosion resistance. The cell culture experiments confirm that the enhanced corrosion resistance assure the biocompatibility of the substrate-coating system. In general, the HA coating prepared in neutral environment shows great potential in surface modification of magnesium alloys.

In vitro study of a novel multi-substituted hydroxyapatite nanopowder synthesized by an ultra-fast, efficient and green microwave-assisted method

In order to improve the biological activity of hydroxyapatite (HA), a multi-substituted HA (SHA) nanopowder with the chemical composition of Ca_9.5Mg_0.25Sr_0.25(PO₄)_5.5(SiO₄)_0.5(OH)_1.2F_0.8 was synthesized using the microwave-assisted method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) revealed that all ions were substituted in the HA crystal lattice. The HA and SHA nanoparticles had a semi-spherical morphology with the average size of 90 and 80 nm, respectively. In-vitro bioactivity assessments showed that after the 28-day immersion of the samples in the simulated body fluid, the morphology of the precipitated apatites on the surface of the HA sample still consisted of spherical particles with a cauliflower-like structure. However, in the SHA sample, the morphology of the precipitated apatites was changed to a nanorod-like one similar to the bone-like apatite, which may be attributed the presence of Sr in the precipitated apatites. The results showed that the release of the substituted ions not only had no adverse effect on the cell viability and cell attachment, but also enhanced the alkaline phosphatase activity of MG63 osteoblast like cells in the SHA group, as compared to the HA and control groups. The results indicated that the simultaneous substitution of Si, Mg, Sr, and F in HA nanoparticles could effectively promote bioactivity, cell proliferation and differentiation. This novel HA composition could be, therefore, well used for implant coating, bone tissue engineering and other orthopedic applications.

Mesoporous silica pellets as bifunctional bone drug delivery system for cefazolin

For decades, bone drug delivery systems dedicated for osteomyelitis treatment have been investigated as bifunctional materials that exhibit prolonged drug release and mineralization potential. Herein, composite-type pellets based on cefazolin-loaded amino-modified mesoporous silica SBA-15 and microwave-assisted hydroxyapatite were investigated as potential bone drug delivery system in vitro. Pellets were obtained by granulation, extrusion and spheronization methods in laboratory scale and studied in terms of physical properties, drug release, mineralization potential, antimicrobial activity and cytotoxicity towards human osteoblasts. The obtained pellets were characterized for hardness and friability which indicated the pellets durability during further investigations. Prolonged (5-day) release of cefazolin from pellets was observed. The pellets exhibited mineralization potential in simulated body fluid, i.e., a continuous layer of bone-like apatite was formed on the surface of pellets after 28 days of incubation. An antimicrobial assay of pellets revealed an antibacterial effect against Staphylococcus aureus strain during 6 days. No cytotoxic effects of pellets towards human osteoblasts were observed. The obtained results proved that proposed pellets appear to have potential applications as bone drug delivery systems.

Microwave processing of calcium phosphate and magnesium phosphate based orthopedic bioceramics: A state-of-the-art review

The main theme of this paper is to review microwave-assisted synthesis and processing of calcium and magnesium phosphate bioceramics. Microwave processing of advanced materials has been an active field of research for the last three decades and has been already reviewed in the literature. Microwave processing of bioceramics is being pursued for almost the same period of time. Unfortunately, to the best of our knowledge, we are not aware of any comprehensive review in the literature. Our group has been a significant contributor to the field, and we feel that it is an appropriate time for reviewing the state-of-the-art of the field. The paper is divided into several sections. After rationalizing the motivation behind writing this paper in the introduction, the second section builds on some fundamental aspects of microwave-matter interactions. The third section, representing the synthesis aspects, is subdivided into five sub-sections focusing on various calcium and magnesium phosphates in both crystalline and amorphous forms. The fourth section focuses on magnesium phosphate-based bioceramics. The fifth and the sixth section describe results on the utility of microwave assistance in developing multi-functional coatings on medical implants and orthopedic cements respectively. The subsequent section reviews results on microwave sintering of calcium and magnesium phosphates. The paper concludes with remarks on unresolved issues and future directions of research. It is expected that this comprehensive review on the interdisciplinary topic will further propel the exploration of other novel applications of microwave technology in processing biomaterials by a diverse group of scientists and engineers. STATEMENT OF SIGNIFICANCE: 1. This review highlights the broad-spectrum capabilities of microwave applications in processing orthopedic bioceramics. 2. The article covers "processing" in the broadest sense of the word, comprising of material synthesis, sintering, coating formation, and setting of orthopedic cements. It also expands beyond conventional calcium phosphates to include the emergent family of magnesium phosphates. 3. In vitro/in vivo responses of microwave-processed bioceramics are discussed thus providing an integral understanding of biological aspects of these materials. 4. The comprehensive review on this interdisciplinary topic will help researchers in various disciplines to appreciate the significance and usefulness of microwaves in biomaterials processing. Further, we also believe that it will propel the exploration of other novel applications of microwave technology in the biomaterials sector.

Effect of Temperature on Drug Release: Production of 5-FU-Encapsulated Hydroxyapatite-Gelatin Polymer Composites via Spray Drying and Analysis of In Vitro Kinetics

In this study, 5-fluorouracil- (5-FU-) loaded hydroxyapatite-gelatin (HAp-GEL) polymer composites were produced in the presence of a simulated body fluid (SBF) to investigate the effects of temperature and cross-linking agents on drug release. The composites were produced by wet precipitation at pH 7.4 and temperature 37°C using glutaraldehyde (GA) as the cross-linker. The effects of different amounts of glutaraldehyde on drug release profiles were studied. Encapsulation (drug loading) was performed with 5-FU using a spray drier, and the drug release of 5-FU from the HAp-GEL composites was determined at temperatures of 32°C, 37°C, and 42°C. Different mathematical models were used to obtain the release mechanism of the drug. The morphologies and structures of the composites were analyzed by X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results demonstrated that for the HAp-GEL composites, the initial burst decreased with increasing GA content at all three studied temperatures. Further, three kinetic models were investigated, and it was determined that all the composites best fit the Higuchi model. It was concluded that the drug-loaded HAp-GEL composites have the potential to be used in drug delivery applications.

Ring opening polymerization of α-amino acids: advances in synthesis, architecture and applications of polypeptides and their hybrids

This review provides a comprehensive overview of the latest advances in the synthesis, architectural design and biomedical applications of polypeptides and their hybrids.

Ionic Liquid-Assisted Hydrothermal Synthesis of a Biocompatible Filler for Photo-Curable Dental Composite: From Theory to Experiment

Nanostructured hydroxyapatite (HA) is a new class of biocompatible fillers which has been recently utilized in bio hybrid materials by virtue of its excellent tissue bioactivity and biocompatibility. However, the need for higher thermal stability, solubility, surface bioactivity, radiopacity, and remineralization ability suggests a divalent cation substitution of HA for use in light curable dental restorative composites. In this work, structural and optical properties of Sr-doped hydroxyapatite were studied using first-principle calculations based on density functional theory (DFT). Next, Sr-doped hydroxyapatite (HA) was prepared via a new ionic liquid-assisted hydrothermal (ILH) route. Samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) surface area analysis, and cell viability. The obtained experimental data showed that the nucleation and crystal growth process controlled by [BMIM]Br molecules results in uniform products with small and regular particles and high specific surface areas. Finally, cytotoxicity tests showed that the as-prepared Sr-doped HA nanoparticles have good biocompatibility (≥91%), confirming their potential for use in photo-curable dental restorative composites.

The bone regeneration capacity of 3D-printed templates in calvarial defect models: A systematic review and meta-analysis

3D-printed templates are being used for bone tissue regeneration (BTR) as temporary guides. In the current review, we analyze the factors considered in producing potentially bioresorbable/degradable 3D-printed templates and their influence on BTR in calvarial bone defect (CBD) animal models. In addition, a meta-analysis was done to compare the achieved BTR for each type of template material (polymer, ceramic or composites). Database collection was completed by January 2018, and the inclusion criteria were all titles and keywords combining 3D printing and BTR in CBD models. Clinical trials and poorly-documented in vivo studies were excluded from this study. A total of 45 relevant studies were finally included and reviewed, and an additional check list was followed before inclusion in the meta-analysis, where material type, porosity %, and the regenerated bone area were collected and analyzed statistically. Overall, the capacity of the printed templates to support BTR was found to depend in large part on the amount of available space (porosity %) provided by the printed templates. Printed ceramic and composite templates showed the best BTR capacity, and the optimum printed template structure was found to have total porosity >50% with a pore diameter between 300 and 400 µm. Additional features and engineered macro-channels within the printed templates increased BTR capacity at long time points (12 weeks). Although the size of bone defects in rabbits was larger than in rats, BTR was greater in rabbits (almost double) at all time points and for all materials used. STATEMENT OF SIGNIFICANCE: In the present study, we reviewed the factors considered in producing degradable 3D-printed templates and their influence on bone tissue regeneration (BTR) in calvarial bone defects through the last 15 years. A meta-analysis was applied on the collected data to quantify and analyze BTR related to each type of template material. The concluded data states the importance of 3D-printed templates for BTR and indicates the ideal design required for an effective clinical translation. The evidence-based guidelines for the best BTR capacity endorse the use of printed composite and ceramic templates with total porosity >50%, pore diameter between 300 and 400 µm, and added engineered macro-channels within the printed templates.

Synthetic Biodegradable Aliphatic Polyester Nanocomposites Reinforced with Nanohydroxyapatite and/or Graphene Oxide for Bone Tissue Engineering Applications

This paper provides review updates on the current development of bionanocomposites with polymeric matrices consisting of synthetic biodegradable aliphatic polyesters reinforced with nanohydroxyaptite (nHA) and/or graphene oxide (GO) nanofillers for bone tissue engineering applications. Biodegradable aliphatic polyesters include poly(lactic acid) (PLA), polycaprolactone (PCL) and copolymers of PLA-PGA (PLGA). Those bionanocomposites have been explored for making 3D porous scaffolds for the repair of bone defects since nHA and GO enhance their bioactivity and biocompatibility by promoting biomineralization, bone cell adhesion, proliferation and differentiation, thus facilitating new bone tissue formation upon implantation. The incorporation of nHA or GO into aliphatic polyester scaffolds also improves their mechanical strength greatly, especially hybrid GO/nHA nanofilllers. Those mechanically strong nanocomposite scaffolds can support and promote cell attachment for tissue growth. Porous scaffolds fabricated from conventional porogen leaching, and thermally induced phase separation have many drawbacks inducing the use of organic solvents, poor control of pore shape and pore interconnectivity, while electrospinning mats exhibit small pores that limit cell infiltration and tissue ingrowth. Recent advancement of 3D additive manufacturing allows the production of aliphatic polyester nanocomposite scaffolds with precisely controlled pore geometries and large pores for the cell attachment, growth, and differentiation in vitro, and the new bone formation in vivo.

Synthesis of Hydroxyapatite with Antibacterial Properties Using a Microwave-Assisted Combustion Method

The prevention of implant-associated infections has been increasing clinically in orthopedic surgery. Hydroxyapatite with antibacterial properties was synthesized using a microwave-assisted combustion method. High crystallinity at low temperature can be achieved using this method. The synthesized hydroxyapatite exhibited a superior clear zone for both Gram-positive and Gram-negative bacteria. Electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) were used for the radical investigation. The application of intelligent ink testing and an antioxidant assay using DPPH reduction were also used to confirm the existence of radicals. These techniques provided data confirming that radicals are responsible for the antibacterial properties. The synthesized antibacterial hydroxyapatite would be a good candidate for the prevention any infection with medical implants and injection materials causing failure in bone repair.

Large-scale and fast synthesis of nano-hydroxyapatite powder by a microwave-hydrothermal method

A microwave-hydrothermal (M-H) method assisted with ultrasonic atomization precipitation was developed for large-scale and fast synthesis of nano-hydroxyapatite (nano-HAP) powder. This technology combines the uniform mixing effect of ultrasonic atomization precipitation at high concentration with the rapid and uniform heating effect of the M-H method, aiming to obtain a high quality product with low agglomeration, homogeneous size distribution, accurate stoichiometry, and high purity while improving the yield. The influences of reaction temperature, reaction time and reactant concentration on the formation of nano-HAP were investigated. The results show that the crystallinity increases significantly and the diameter of nano-HAP increases to some extent, but the length does not change obviously while the reaction temperature increase from 60 °C to 160 °C and the reaction time increases from 1 minute to 40 minutes respectively. The crystallinity, dispersion and crystal size of nano-HAP do not change obviously while the concentration of Na₂HPO₄·12H₂O increases from 0.06 mol L⁻¹ to 0.4 mol L⁻¹. When the reaction temperature is 160 °C, the reaction time is 40 min, and the concentration of Na₂HPO₄·12H₂O is 0.4 mol L⁻¹, the yield of nano-HAP powder achieved a maximum yield (0.033 kg L⁻¹). The obtained nano-HAP powder exhibits a uniform size and good dispersibility, with a size of 87.62 ± 22.44 nm and crystallinity of 0.92, respectively. This study indicates that the M-H method assisted with ultrasonic atomization precipitation is a facile one-pot method for the rapid and large-scale synthesis of highly crystalline, dispersible nano-HAP particles.

The obtained nano-HAP still has high crystallinity, uniform size and good dispersibility when the concentration of Na₂HPO₄ is 0.4 mol L⁻¹.

From monetite plate to hydroxyapatite nanofibers by monoethanolamine assisted hydrothermal approach

Calcium phosphates offer outstanding biological adaptability. Thanks to their specific physico-chemical properties they are one of the most widely used materials in bone tissue engineering applications. The search for an innovative and economic strategy of synthesizing their different forms has been drawing considerable attention in the field. Herein, we report on a facile hydrothermal process in the presence of ethylenediamine tetraacetic acid and monoethanolamine to obtain various forms of calcium phosphates. The monoethanolamine served as an alkaline source and crystal growth modifier, while ethylenediamine tetraacetic acid was used to control the Ca²⁺ supersaturation level under high temperature and high pressure conditions. The obtained inorganic compounds were examined for their elemental composition, morphology, and structure using scanning electron microscopy, Raman spectroscopy, and powder x-ray diffraction. We were able to selectively synthesize monetite plate-like microcrystals as well as hydroxyapatite plates and nanofibers by simply varying the concentration of monoethanolamine.