n-HAp Powder Research Articles

Comparison of crude nano-hydroxyapatite extracted from calcified seaweed in terms of composition, antibacterial activity, and cytotoxicity

The objectives of this study were to synthesize nano-hydroxyapatite (nHAp) from red seaweed by an optimized and environmentally friendly thermal and chemical treatment method using minimal chemicals. Calcified tissues from seaweed were thermally treated to obtain calcium carbonate, which reacted with potassium dihydrogen phosphate to synthesize nHAp. Nano-hydroxyapatite materials, nHAp-Jr and nHAP-Co were produced from the seaweeds Jania rubens and Corallina officinalis, respectively. Results showed that the developed method successfully produced high yields of nHAp-Jr and nHAp-Co powders (>78 %). The crude composition of the synthesized nHAp-Jr and nHAp-Co materials was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scan electron microscopic (SEM), Energy dispersive X-ray spectroscopy (EDAX), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), and thermal gravimetric analysis (TGA). XRD patterns confirmed the formation of nHAp and calcium phosphate phases. SEM images showed the nanoparticle size of nHAp-Jr and nHAp-Co with an average distribution of 16.70 ± 0.71 nm. EDAX spectra identified the relative similar elemental compositions of nHAp-Jr and nHAp-Co. BET and BJH patterns revealed relatively similar specific surface area, total pore volume and average pore diameter for mesoporous size nHAp powders (2–50 nm). Antibacterial activity of nHAp-Jr and nHAp-Co showed good efficacy against the caries-causing agent, Streptococcus mutans compared to ciprofloxacin using the modified XTT assay. Cytotoxicity testing of nHAp-Jr and nHAp-Co against WISH cell line using modified MTT assay confirmed the relevant antibacterial effects without any side effect on hepatocytes. This sustainable method produced nHAp compounds from seaweed that show promising antibacterial properties and biocompatibility, highlighting the potential for biomedical applications.

Influence of Fish Scale-Based Hydroxyapatite on Forcespun Polycaprolactone Fiber Scaffolds.

Marine waste byproducts, especially fish scales, have proved to be one of the most prominent sources for developing sustainable materials for various applications including biomedical applications. Hydroxyapatite (HAp), being one of such biomaterials that can be synthesized from the massive fish-based waste, has received plentitude of attention due to its excellent ability to promote cell growth and proliferation. However, understanding the influence of HAp on polymer matrices that are tailored for biomedical applications is still a challenge. This study is intended to develop a sophisticated yet inexpensive method to obtain nonwoven polycaprolactone (PCL) nanofibrous scaffolds and analyze the influence of calcium-deficient nanoporous hydroxyapatite (n-HAp) on the thermal, mechanical, and biological properties of these scaffolds. The n-HAp is synthesized using two different types of fish scales, carpa (CA) and pink perch (PP), by calcination followed by nanomilling. The synthesized n-HAp powder is characterized by using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The PCL fibrous scaffolds were developed using a novel forcespinning technique with n-HAp as the filler. The morphology of the scaffolds was characterized using SEM and Raman spectroscopy. SEM and TEM results have confirmed the size reduction of the HAp powder after nanomilling. Thermal properties were analyzed using thermogravimetric analysis and differential scanning calorimetry. The major degradation temperature has increased by 3° and was observed to be 398° for 1 wt % filler loading for both carpa and pink perch-derived n-HAp. The increase in filler content has increased the residue left after decomposition and is 4% for 5 wt % filler loading. The crystallinity percent has increased by 7% compared to neat fibers for 1 wt % filler loading. Mechanical properties were tested using tensile tests. The tensile test strength has shown 32% improvement for 1 wt % compared to neat fibers. Cell viability tests were performed using hFOB cells which have shown significant cell growth for a high filler loading of 5 wt %. The results suggest that both CA-n-HAP and PP-n-Hap-incorporated fibrous scaffolds can be used potentially for biomedical applications after careful investigation of the scaffold behavior with longer incubation periods.

Effects of Homemade Nano-Hydroxyapatite and Olive Oil Paste on Remineralization of Early Caries Lesions

Nano-hydroxyapatite (nHAP) particles are a new generation of materials reported to remineralize enamel lesions. The purpose we aimed was to compare the in vitro effects of fluoride gel, sodium fluoride toothpaste, and homemade nHAP paste on remineralizing artificial early enamel caries. Methods: Incipient caries were induced in 21 extracted, sound premolar teeth by storing each specimen in a demineralization solution for 72 hours, followed by pH cycling. The samples (n= 7, each) were then treated with 2% neutral fluoride gel, 0.25% sodium fluoride toothpaste, or homemade nHAP paste, comprising a mixture of nHAP powder and olive oil. After demineralization and remineralization, the results were compared using the DIAGNOdent pen (KaVo, Germany). The data were statistically analyzed using paired t-tests and a one-way ANOVA test. Outcomes: The degree of demineralization in each of the three groups (fluoride gel group, 15.71; sodium fluoride dentifrice group, 15.28; nHAP paste group, 16.71) was significantly elevated compared to baseline (3, 2.5, 2.28, respectively); however, no significant difference was observed between the remineralization readings in each of the three groups (6, 7, 5.5, respectively) (p > 0.05). In conclusion, we concluded that the homemade nHAP paste had a beneficial effect on the remineralization of initial enamel caries lesions.

PL, TL and Persistent Luminescence Characterization of Undoped and Eu Doped Nanostructured Hydroxyapatite

Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) possesses the closest mineralized structure to natural bone tissue and has been widely using in as bone substitutes and for various biomedical applications. Undoped and doped with rare earth elements HAps are the basis of promising biomedical imaging, bone tissue engineering, gene and drug delivery applications. In the present work, we present the results of investigation of the photoluminescence (PL), thermoluminescence (TL) and persistent luminescence (PersL) of synthetic nanostructured HAp (n-HAp). Undoped and Eudoped (0.0, 0.1, 0.5, 1.0, 2.0 mol %) n-HAp powders were synthesized by solution-precipitation method and characterized by SEM-EDS, FTIR and Raman techniques. The 3D excitation-emission spectrum of undoped n-HAp exhibits a broad band with excitation/emission maximum at 376/454 nm, respectively. The maximum position slightly shifts to shorter excitation and emission wavelengths with increases of the Eu concentration that could be due to a possible overlapping between the Eu emission band and intrinsic emission of undoped n-HAp. It was found that (similarly to behavior of PL in Si nanocrystals, Xin et al., RSC Adv., 2019, 9, 8310) the emission peak is red-shifted as the excitation wavelength red-shifts. The typical Eu3+ emission bands were observed for high Eu doping concentrations. TL glow curves of n-HAp samples exposed to beta radiation from Sr-Y source display a broad TL peak with maxima in-between 145 and 165 oC depending on the Eu concentration. The highest TL intensity is observed for undoped n-HAp, showing quenching effect of Eu on TL emission. This TL quenching effect contrasted with the PersL decay emission measured immediately after irradiation exposure, which was highest for 0.1 mol % Eu. The intrinsic defects in n-HAp host is related to the PL, TL and PersL emissions; however, the nature of the radiative and non-radiative recombination mechanisms requires further investigation. The PL, TL and PersL of undoped HAp may have prospective application in the fields of radiation detection, ionizing radiation dosimetry and biomedical imaging. Keywords: Hydroxylapatite, thermoluminescence, persistent luminescence.

Preparation and characterization of Fe doped n-hydroxyapatite for biomedical application

Natural and synthetic biomaterials are often used in clinical utilization to assist, strengthen and to restore impaired tissue or biological functions. Iron doped bioactive nano-crystalline hydroxyapatite (Fe doped n-HAp) powder with different concentrations of Fe was successfully synthesized by the reflux method. The crystallinity of the samples was confirmed by powder XRD analysis and in 0.2 M Fe doping, the smallest crystalline size of 3.2 nm was obtained. SEM results indicate that higher concentration of Fe content has a considerable impact on the morphology of n-HAp material. The functional group assignments and the iron dopant incorporation has been analyzed and confirmed through FTIR and Raman results. The antibacterial activity test of Fe doped n-HAp mixed with amoxicillin antibiotic displays good inhibition to the bacterial strains.

Effective removal of cationic methylene blue dye using nano‐hydroxyapatite synthesized from fish scale bio‐waste

AbstractNano‐hydroxyapatite (NHAp) with a novel rod shape was synthesized from an economical and easily accessible Labeo rohita fish scale bio‐waste by facile and straightforward alkaline heat treatment method. The purity, functionality, morphology, and surface area of the green synthesized NHAp powder were well‐characterized via X‐ray diffraction (XRD), Fourier‐transform infrared (FT‐IR) spectroscopy, transmission electron microscopy (TEM), and Brunauer‐Emmett‐Teller (BET). The TEM and BET results indicate that the apatite is prepared as a rod‐like particle and highly porous with high surface area (112.36 m2 g−1). The NHAp powder was used for the adsorptive removal of cationic dye‐methylene blue (MB) from the aqueous samples. Batch experiments were performed to evaluate the mechanism of adsorption and kinetic models. The NHAp achieved an enhanced adsorption efficiency (666.67 mg g−1) for the adsorption process. The obtained results perfectly obeyed the pseudo‐second‐order model, and the Langmuir isotherm exhibited an excellent relationship with the experimental data. Furthermore, thermodynamic studies reveal that the adsorption process was exothermic and spontaneous. Thus, the results proved that Labeo rohita fish scale bio‐waste derived NHAp can be inventively utilized as a cost‐effective and eco‐friendly adsorbent for wastewater treatment.

Three-dimensional nano-hydroxyapatite sodium silicate glass composite scaffold for bone tissue engineering - A new fabrication process at a near-room temperature

Hydroxyapatite nanoparticles (n-HAp) due to their structural similarity to the mineral part of human bone is one of the most promising materials for the preparation of highly biocompatible and osteoconductive scaffolds to be used in bone tissue regeneration. Yet, the conversion of n-HAp powder into a 3D scaffold is usually occurring by sintering at high temperatures for several hours. Such a high temperature process, strongly affects the physicochemical and biological properties of n-HAp and therefore losing their similarity to the human bone tissue. In the present study, sodium silicate solution is applied, for the first time, as a mineral binder for consolidation of n-HAp through a dehydration-drying process at a near-room temperature (37 °C). The new consolidation process preserves the low crystallinity, non-stoichiometry, and nanosize of the precursor n-HAp, so important to mimic bone tissue. Furthermore, the consolidated 3D composite scaffold presents an adequate porosity and mechanical profile required for bone-healing applications. The in vitro cytotoxicity tests proved the non-hazardous and inductive nature of the fabricated 3D composite over the MG-63 osteoblast-like cell line. In fact, the results show significantly enhanced cell proliferation. Overall, this new consolidation process can deliver a porous 3D composite scaffold with high potential for bone tissue engineering applications.

Fabrication and Characterization of Nanocrystalline Hydroxyapatite Extracted from Bovine Bone at Different Calcination Temperatures

Hydroxyapatite (HAP) is a calcium phosphate based bioceramics and a basic mineral component of teeth and bones of vertebrates. Its chemical and structural features are analogous to the inorganic components of bone. The present work focuses on the fabrication and characterizations of nanocrystalline HAP extracted from bovine bone at different calcination temperatures (600, 800, and 1000°C) without the use of chemicals/solvents. Therefore, it is a green technology. The characterizations of the extracted n-HAP were carried out by X-ray diffraction (XRD), Fourier transforms infrared (FTIR) and Field emission scanning electron microscopy (FESEM) The FTIR results confirmed the presence of phosphate PO4-3, hydroxyl OH-1 and carbonate CO3-2 groups in the n-HAP powder. FESEM observation confirmed the hexagonal rod like structure. XRD analysis revealed that extracted n-HAP has a hexagonal crystal structure and crystallite size was in the range of 10.48-84.08 nm. Crystallinity degree and crystallite size gradually increased with the intensification of calcination temperature from 600 °C -1000 °C.

Mechanical properties improvement of epoxy composites by natural hy-droxyapatite from fish scales as a fillers

This study was carried out to prepare epoxy/ natural hydroxyapatite composite for potential biomedical application. Natural hydroxyapatite (nHAp) powder was extracted from Tilapia fish scales via the thermal method. The natural hydroxyapatite was milled for 48 hours and dried by spray method. The nHAp particle size was determined using mastersizer 2000 particle size analyser and the chemical structure was confirmed using (XRD) and FTIR analysis. The particle size of nHAp was identified to be between 1 and 10 microns. Mechanical properties of epoxy/ natural hydroxyapatite were investigated by using impact and flexural test. The highest flexural strength of epoxy/nHAp composite was recorded when the nHAp filler was 10 wt% which is 77 % increment as compared to epoxy alone. The impact strength was increased up to two-fold as compared to neat epoxy. The scanning electron micrograph (SEM) and EDX analysis showed uniform dispersion of nHAp particles within the epoxy matrix for the composites with 10 wt% filler loading.

Risedronate-Loaded Macroporous Gel Foam Enriched with Nanohydroxyapatite: Preparation, Characterization, and Osteogenic Activity Evaluation Using Saos-2 Cells.

The application of minimally invasive surgical techniques in the field of orthopedic surgery has created a growing need for new injectable synthetic materials that can be used for bone grafting. In this work, novel injectable thermosensitive foam was developed by mixing nHAP powder with a thermosensitive polymer with foaming power (Pluronic F-127) and loaded with a water-soluble bisphosphonate drug (risedronate) to promote osteogenesis. The foam was able to retain the porous structure after injection and set through temperature change of PF-127 solution to form gel inside the body. The effect of different formulation parameters on the gelation time, porosity, foamability, injectability, and in vitro degradation in addition to drug release from the prepared foams were analyzed using a full factorial design. The addition of a co-polymer like methylcellulose or sodium alginate into the foam was also studied. Results showed that the prepared optimized thermosensitive foam was able to gel within 1min at 37°C, and sustain the release of drug for 72h. The optimized formulation was further tested for any interactions using DSC and IR, and revealed no interactions between the drug and the used excipients in the prepared foam. Furthermore, the ability of the pre-set foam to support osteoblastic-like Saos-2-cell proliferation and differentiation was assessed, and revealed superior function on promoting cellular proliferation as confirmed by fluorescence microscope compared to the plain drug solution. The activity of the foam treated cells was also assessed by measuring the alkaline phosphatase activity and calcium deposition, and confirmed that the cellular activity was greatly enhanced in foam treated cells compared to those treated with the plain drug solution only. The obtained results show that the prepared risedronate-loaded thermosensitive foam would represent a step forward in the design of new materials for minimally invasive bone regeneration.

Preparation and Using Modified Nanohydroxyapatite Molecules for Wastewater Treatment

Today, the use of municipal wastewater (WW) as the alternative source of water for irrigation purpose is a common practice. This study will address the effect of using synthetic nanohydroxyapatite (nHAp) powders, which is prepared by microwave heating based wet chemical method and its modification with humic acid (HA) as a sorbent and stabilizing agents to remove contaminants from wastewater. The nHAp and nHAp-HA complex were characterized by different techniques. The wastewater treatment process was done by using a fixed bed column model by adsorption onto nHAp or nHAp-HA complex. The flow rate of the wastewater purification process was 80 ml/h for each 10 g of nHAp or nHAp-HA complex for treat 1 l. Some WW properties were determined before and after the treatment process, such as total organic carbon (TOC), heavy metals, major cations, major anions, electrical conductivity (EC), and pH. The results of this study indicated that TOC was completely removed from WW and removed by a 97.5% ratio by nHAp-HA complex and nHAp, respectively. In addition, cadmium, zinc, chromium, and lead were completely removed from the WW by a nHAp or nHAp-HA complex. Moreover, other heavy metals (copper, manganese, cobalt, iron, boron, and selenium), sodium adsorption ratio (SAR), total dissolved solids (TDS), EC, and pH of the treated wastewater (TWW) by the nHAp and modified nHAp were within the acceptable range of irrigation. Thus, nHAp and modified nHAp may be easily applied to treat the wastewater and be using it for irrigation purposes.

Effects of ultrasonic agitation time on wet chemical synthesis of nanohydroxyapatite

In this study, the synthesis of the nanohydroxyapatite (nHAp) powders by way of wet chemical method is reported. Calcium nitrate tetrahydrate (Ca(NO3)2·H2O) and dibasic ammonium phosphate ((NH4)2HPO4) were used as calcium and phosphorus sources, respectively. The effect of ultrasonic agitation time has been systematically studied between 30 and 150 min at the temperature of 70°C. Structural, morphological, spectroscopic and thermal analysis have been carried out by way of X-ray powder diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy and thermogravimetry–differential scanning calorimetry analysis. It is shown that the ultrasonic agitation conditions significantly affect the crystallite size, dislocation density and microstrain of the powders calculated by way of the Debye–Scherrer formula. Thermal analyses reveal that the ultrasonic agitation treatment has a very beneficial effect on the fabrication of the powders by the wet chemical method due to the inhibition of physisorbed and chemisorbed water and the calcium deficiency. Magnetic stirring treatment is found to lead to larger nHAp nanoparticle agglomerations due to more water absorption. The results offer a promising route towards the scalable synthesis of the pure-phase nHAp powders with controllable structural and morphological properties, which could be useful in various types of basic and applied research on HAp-based materials.

The Effects of Ageing Time on the Preparation of Nano-Hydroxyapatite by Chemical Precipitation Method

Nano-hydroxyapatite(nHAp) powders were prepared by chemical precipitation method using Ca(NO3)2·4H2O and (NH4)2HPO4 as raw materials and deionized water as solvent. To investigate the influence of ageing time on the preparation of nano HAp powder by changing the ageing time. And the composition and appearance of the samples were analyzed by infrared spectroscopy (FTIR), X ray diffraction (XRD) and scanning electron microscopy (SEM). With the longer ageing time, the samples gradually became sphere-like crystals and the crystallization degree were better.

Implant application of bioactive nano-hydroxyapatite powders—a comparative study

Hydroxyapatite (HAp) is commonly used as a bone-substitute material because of its bioactive and biocompatible properties. The aim of the present study is to compare the two different types of nano-HAps powders, to ascertain their properties in a biological environment. The nano-HAps powders were synthesized in two ways (i) chemical method by co-precipitation (cHAp) (ii) natural method by calcination of goat femur bone (nHAp). The cHAp and nHAp powders were analyzed by x-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis to find out the crystallinity, morphology, particle size and phase changes of the samples respectively. High crystallinity and controlled morphology were observed in nHAp compared to cHAp. In-vitro studies such as biodegradation, protein adsorption and hemolysis were carried out to determine the biocompatibility nature of these nanoparticles. It was found that, both cHAp and nHAp nano powders are active in the biological environment. On comparison, nHAp nanoparticles showed better performance than cHAp.

Polyvinyl Alcohol-Nanobioceramic Based Drug Delivery System

Drug delivery research today is an advanced and important area in pharmaceutical research and application of nanotechnology includes enhancement of the solubility and permeability of the drugs so as to improve their bioavailability including delivery to the targeted site. Hydroxyapatite (HAP) based bioceramic nanoparticles composed of biodegradable polymers have been used in the present work to develop an amoxicillin based delivery systems. The synthesized n-HAP powders were estimated for the Ca/p ratio. This ratio indicates the presence of HAP as a single phase. The nano structure, morphology and presence of vibrational groups are con- firmed using instrumental analysis. The SEM images show the spherical shaped particles of nano hydroxyapatite are confirmed. The loading and unloading characteristics of the drug were recorded spectro photometrically.

Alginate-based bipolymeric-nanobioceramic composite matrices for sustained drug release

Alginate-based bipolymeric–nanobioceramic composite matrices for sustained drug release were developed through incorporation of nano-hydroxyapatite [nHAp] powders within ionotropically-gelled calcium ion-induced alginate-poly (vinyl pyrrolidone) blends polymeric systems. nHAp powders were synthesized by precipitation technique using calcium hydroxide [Ca(OH)2] and orthophosphoric acid [H3PO4] as raw materials. The average particle size of these was synthesized. nHAp powders was found as 19.04nm and used to prepare nHAp-alginate-PVP beads containing DS. These beads exhibited drug entrapment efficiency (%) of 65.82±1.88 to 94.45±3.72% and average bead sizes of 0.98±0.07 to 1.23±0.15mm. These beads were characterized by scanning electron microscopy (SEM) and Fourier transform-infra red (FTIR) spectroscopy analyses. Various nHAp-alginate-PVP beads containing DS exhibited prolonged sustained drug release and followed the Koresmeyer–Peppas model of drug release (R2=0.9908–0.9978) with non-Fickian release (anomalous transport) mechanism (n=0.73–0.84) for drug release over 8h.

Bio-Hybrid Scaffolds for Bone Tissue Engineering: Nano-Hydroxyapatite/Chitosan Composites

Natural bone ECM is a hierarchical nanocomposite made of an inorganic phase deposited within an organic matrix. In order to mimic the bone highly organized hybrid structure and functionality, strategies that allow assembling ceramic and polymer phase can be applied. To this aim, we investigated aninsitugrowth method able to nucleate a nanoHydroxyapatite (nHAp) phase into and around the interconnected porous structure of chitosan sponges. By increasing the calcium and phosphate concentration in the meta-stable solution used for the nHAp nucleation, the inorganic phase raised proportionally, in the range 10%-30% wt. In order to be compared with nHAp loaded scaffolds, pure chitosan samples have been produced by cross-linking biopolymer with arginine. Moreover, nHAp loaded samples, containing the 20 % wt of inorganic phase have been prepared by simply mixing low crystalline nHAp powders with the chitosan gel. Thein situnucleation method highlighted evident advantages in terms of nanophase distribution and mechanical performances with respect to a merely mixing procedure.

Influence of zinc incorporation on microstructure of hydroxyapatite to characterize the effect of pH and calcination temperatures

This work was focused to study the existence of Zn2+ in structure, chemical composition as well as particle and crystallite size of hydroxyapatite (HAp) to characterize the effect of pH of the solution and calcination temperature. Non-stoichiometric HAp (nHAp) powders containing 4 at.% zinc fraction were synthesized via solution–precipitation method. In order to characterize the effect of pH (values: 9 and 10.5) and two calcination temperatures (550 and 1000 °C) on chemical composition, molecule internal bonds, particle and crystallite size of the synthesized powders, XRD, EDS, FTIR and SEM techniques were utilized. The results showed that zinc cations could be incorporated in the HAp atomic structure to form low crystalline single phase of nHAP. The pH adjustment to 10.5 caused the formation of powders with smaller particle and crystallite sizes. The results also indicated that calcination temperature up to 1000 °C caused decomposition of zinc doped nHAp to β-tri calcium phosphate and tri zinc calcium phosphate phases which are used to control the speed of biodegradation.

Synthesis of alginate bioencapsulated nano-hydroxyapatite composite for selective fluoride sorption

This article focuses on the development of eco-friendly adsorbent by alginate (Alg) bioencapsulating nano-hydroxyapatite (n-HAp) namely n-HApAlg composite for defluoridation studies in batch mode. n-HAp powder utilized as a promising defluoridating material, but it causes a significant pressure drop during field applications. To overcome such technological bottlenecks, n-HApAlg composite was synthesized. The defluoridation capacity (DC) of synthesized n-HApAlg composite possesses an enhanced DC of 3870mgF−/kg when compared to n-HAp and calcium alginate (CaAlg) composite which possess DC of 1296 and 680mgF−/kg, respectively. The biocomposite features were characterized using FTIR and SEM with EDAX analysis. The various adsorption influencing parameters like contact time, pH, co-anions, initial fluoride concentration and temperature were optimized. The adsorption process was enlightened by various isotherms and kinetic models. The suitability of the biocomposite at field conditions was also tested.

Influence of the Precipitation Temperature on Properties of Nanohydroxyapatite Powder for the Fabrication of Highly Porous Bone Scaffolds

The aim of the present work is to study the influence of the precipitation temperature in the synthesis of nanohydroxyapatite (n-HAp) on the properties of the resulting n-HAp powder for the fabrication of highly porous scaffolds for bone tissue engineering. The n-HAp powder was obtained by a wet precipitation technique starting from calcium nitrate tetrahydrate (Ca (NO3)2*4H2O) and phosphoric acid (H3PO4) at different temperatures: 10°C, 37°C and 50°C. Highly porous scaffolds were fabricated using the three different powders by the sponge replica method and sintering at 1300°C. Combined X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses on powders indicated that on increasing the precipitation temperature the formation of pure n-HAp is accelerated, without significant changes in particles morphology and size. Scaffolds characterized by high porosity (89%) and good compressive strength (0.53 MPa for n-HAp prepared at 37°C) were obtained. XRD analyses on sintered n-HAp confirmed the thermal stability of the material. Therefore, the as-synthesized n-HAp powder can be successfully used for the fabrication of highly porous scaffolds as bone substitutes.