Calcium phosphate grafts produced by rapid prototyping based on laser cladding

Rapid prototyping based on laser cladding by powder injection has been used to produce calcium phosphate three-dimensional grafts without using molds. Precursor material comprising of hydroxyapatite (HA) powder was irradiated by means of an infrared Nd:YAG laser. The processing parameters and the thermal history of the processed material have been assessed and the process has been optimized to obtain solid parts. Processing by laser cladding lead to complete dehydroxylation of the precursor HA, the obtained microstructure is composed by an alpha-tricalcium phosphate (α-TCP) matrix with nucleated tetracalcium phosphate (TTCP) grains, in coexistence with oxyapatite and amorphous calcium phosphate. The produced bioceramic grafts were observed to be bioactive, leading to calcium-deficient hydroxyapatite precipitation and promoting pre-osteoblastic cell attachment and proliferation during “in vitro” cell culture test.     

Fabrication of a Novel Biocompatible Magnetic Biomaterial with Hyperthermia Potential

Preparation and characterization of a novel biocompatible magnetic biomaterial having hyperthermia potential is reported in this study. Fe³⁺ and Ni²⁺ (2:1) cosubstituted hydroxyapatite nanoparticles were synthesized by simple wet precipitation method followed by freeze‐drying which on heat treatment at 1150°C yielded the above mentioned biocompatible magnetic biomaterial composed of hydroxyapatite and β‐tricalcium phosphate along with nickel ferrite. The product was characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscope along with composition analysis. The magnetic behavior was analyzed by vibrating sample magnetometer and biocompatibility was assessed by testing the toxicity on Hela cells using MTT assay. The hyperthermia potential of the material was studied using induction heating. The prepared material has the potential to generate sufficient heat that could be easily controlled by magnetic field parameters and amount of sample. Hence, it can be a potential candidate for making implantable thermoseed for hyperthermia treatment.     

Simple and Rapid Synthesis of Magnetite/Hydroxyapatite Composites for Hyperthermia Treatments via a Mechanochemical Route

This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments.     

Effect of biogenic and synthetic starting materials on the structure of hydroxyapatite bioceramics

In this study, a synthesis of hydroxyapatite by wet-chemical precipitation route was conducted, using a number of calcium oxide sources. Two biogenic calcium carbonates, which are common in nature, i.e. bird eggshells (Gallus gallus domesticus) and land snail shells (from Arianta arbustorum), as well as commercially available synthetic calcium oxides were used as calcium oxide sources. Calcium oxide starting materials and synthesised calcium phosphate products were investigated. Hydroxyapatite bioceramics obtained from the calcium oxides of different origins had significant differences in microstructure after thermal treatment. Microelement analysis of hydroxyapatite products by inductively coupled plasma mass spectroscopy (ICP-MS) showed that they incorporate different amounts of microelements. The microstructure parameters of the obtained bioceramics were influenced by the presence of multiple trace elements in the structure of hydroxyapatite, which also significantly influenced the crystal lattice parameters. The origin of the calcium oxide starting material has a significant impact on the physicochemical properties and quality of bioceramic implants and, therefore, could also affect the biological properties of these materials.     

溶胶-凝胶法二氧化钛薄膜诱导沉积磷酸钙层

碳／碳复合材料作为骨植入材料具有良好的生物力学相容性，但没有生物活性。以玻璃片为基板进行预试，发现溶胶凝胶法制备的锐钛矿型二氧化钛薄膜呵在快速钙化溶液中诱导沉积出由磷酸八钙和羟基磷灰石组成的磷酸钙层，二氧化钛薄膜的微观形貌对快速钙化溶液中磷酸钙沉积物的沉积速度和组成影响不大。在以上预试的基础上，通过溶胶凝胶法制备的二氧化钛薄膜在碳/碳复合材料上复合了生物活性磷酸钙涂层。     

How geometry,size, and surface properties of tailor-made particles control the efficiency of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite nanocomposites

Bioactive calcium phosphate nanoparticles as reinforcing filler have widely been used to produce polymer nanocomposite scaffolds suitable for application in bone tissue engineering; however, no study has investigated the effect of geometry, size, and surface properties of these nanoparticles on physical and mechanical behavior of scaffolds. This study was therefore devoted to determine how the critical features of the reinforcing nanoparticles could tailor the efficiency of polymeric nanocomposites. For this, we developed fibrous nanocomposite systems in which poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, was combined with hydroxyapatite (HA) nanoparticles having different sizes, geometries, surface chemical groups, and concentrations. The results showed that critical properties could be controlled by incorporating appropriate amounts of nanoparticles with a specific geometry and surface properties. It was also seen that the tensile modulus of fibrous nanocomposite increased from 77 MPa for neat PHBV to about 161 MPa for the nanocomposites containing 15 wt% surface-modified nanoparticles with elongated morphology.     

Formation of organic-inorganic composite materials based on cellulose <Emphasis Type="Italic">Acetobacter xylinum</Emphasis> and calcium phosphates for medical applications

The formation of composites based on the cellulose Acetobacter xylinum and calcium phosphates has been investigated using X-ray diffraction, electron diffraction, electron microscopy, energy-dispersive analysis, and differential scanning calorimetry. It has been demonstrated that the planar morphology of calcium phosphate nanoparticles capable of interacting with nanofibrils of the cellulose matrix is an important factor providing interfacial contacts in the formation of organic-inorganic composite materials. It has been established that magnesium-containing calcium phosphates represent two-phase systems consisting of calcium magnesium phosphate Ca_2.6Mg_0.4(PO₄)₂ (whitlockite) and hydroxyapatite Ca₅(PO₄)₃(OH). The biocompatibility of the composite materials based on two-phase calcium phosphate systems and the temperature range of their stability (∼20–250°C) determined by the thermal stability of the organic component have been investigated.     

Apatitic calcium phosphates used in compression: rationalization of the end-use properties

Different apatitic calcium phosphates used as direct compression excipients have been developed in the last years. The difficulty to obtain reproducible synthesis explains their approximative and irregular composition. TRI-TAB® commercial grade called anhydrous tricalcium phosphate is associated to a chemical formula corresponding to a mixture of tricalcium phosphate (Ca₃(PO₄)₂) and calcium hydroxide (Ca(OH)₂). The chemical analysis shows that it is hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂).

The purpose of this work is to rationalize the chemical and physical natures of apatitic calcium phosphates used in direct compression, and thus their technological properties. Apatitic calcium phosphates differing in their Ca/P molar ratio (from 1.500 i.e. tricalcium phosphate to 1.667 i.e. hydroxyapatite) have been synthesized and their compression properties have been analysed. The results have been compared to those of TRI-TAB®. They pointed out the importance of the chemical nature contribution. Tricalcium phosphate-based materials exhibited an excellent compactibility when not calcined. Uncalcined hydroxyapatite had similar properties than TRI-TAB®, that is intermediate. Calcined tricalcium phosphate and hydroxyapatite showed a low compaction ability. It appears that the perfect chemical and physical control of the material is important in particle design to rationalize and optimise the tablet formulation as well as the process.     

Fabrication of biphasic calcium phosphates nanowhiskers by reflux approach

Nanowhiskers of biphasic calcium phosphates composed of monetite/hydroxyapatite were fabricated using a cost-effective reflux hydrothermal approach from calcium nitrate and ammonium hydrogen phosphate precursors in presence of urea. The produced nanowhiskers were characterized using, FT-IR-spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron micrograph (TEM) and BET surface area determination. The major phase in Biphasic was (monetite, CaHPO₄.) and their grown crystals were morphologically formed with irregular sizes of well defined rod or whiskers crystal structure. The specific surface area of these fabricated nanowhiskers was found to be 8.48?m²/g according to BET studies. The N₂ adsorption/desorption isotherm of the as prepared monetite calcium phosphate is of type IV indicating that this material has a mesoporous structure. The produced nanowhiskers had 80% of monetite and 20% is hydroxyapatite. By controlling the parameters of the reflux approach it is possible to manipulate the composition and the size of these produced nanowhiskers.     

高纯度羟基磷灰石纳米功能材料的制备工艺

本文利用碳酸钙高温分解得到的氧化钙和磷酸为原料，通过湿式法制备医用生物活性陶瓷羟基磷灰石(HAP)。用X射线衍射(XRD)、傅立叶变换红外光谱(FTIR)等技术对陶瓷材料的组织结构和化学组成进行分析。结果表明在适当工艺条件下。得到的钙磷陶瓷产物为高纯度的羟基磷灰石纳米材料。该方法容易操作，重复性好，适于大批量工业生产，是制备高纯度羟基磷灰石纳米功能材料的理想方法。     

Chitosan Fibers Modified with HAp/β-TCP Nanoparticles

This paper describes a method for preparing chitosan fibers modified with hydroxyapatite (HAp), tricalcium phosphate (β-TCP), and HAp/β-TCP nanoparticles. Fiber-grade chitosan derived from the northern shrimp (Pandalus borealis) and nanoparticles of tricalcium phosphate (β-TCP) and hydroxyapatite (HAp) suspended in a diluted chitosan solution were used in the investigation. Diluted chitosan solution containing nanoparticles of Hap/β-TCP was introduced to a 5.16 wt% solution of chitosan in 3.0 wt% acetic acid. The properties of the spinning solutions were examined. Chitosan fibers modified with nanoparticles of HAp/β-TCP were characterized by a level of tenacity and calcium content one hundred times higher than that of regular chitosan fibers.     

Medicated Scaffolds Prepared with Hydroxyapatite/Streptomycin Nanoparticles Encapsulated into Polylactide Microfibers

The preparation, characterization, and controlled release of hydroxyapatite (HAp) nanoparticles loaded with streptomycin (STR) was studied. These nanoparticles are highly appropriate for the treatment of bacterial infections and are also promising for the treatment of cancer cells. The analyses involved scanning electron microscopy, dynamic light scattering (DLS) and Z-potential measurements, as well as infrared spectroscopy and X-ray diffraction. Both amorphous (ACP) and crystalline (cHAp) hydroxyapatite nanoparticles were considered since they differ in their release behavior (faster and slower for amorphous and crystalline particles, respectively). The encapsulated nanoparticles were finally incorporated into biodegradable and biocompatible polylactide (PLA) scaffolds. The STR load was carried out following different pathways during the synthesis/precipitation of the nanoparticles (i.e., nucleation steps) and also by simple adsorption once the nanoparticles were formed. The loaded nanoparticles were biocompatible according to the study of the cytotoxicity of extracts using different cell lines. FTIR microspectroscopy was also employed to evaluate the cytotoxic effect on cancer cell lines of nanoparticles internalized by endocytosis. The results were promising when amorphous nanoparticles were employed. The nanoparticles loaded with STR increased their size and changed their superficial negative charge to positive. The nanoparticles’ crystallinity decreased, with the consequence that their crystal sizes reduced, when STR was incorporated into their structure. STR maintained its antibacterial activity, although it was reduced during the adsorption into the nanoparticles formed. The STR release was faster from the amorphous ACP nanoparticles and slower from the crystalline cHAp nanoparticles. However, in both cases, the STR release was slower when incorporated in calcium and phosphate during the synthesis. The biocompatibility of these nanoparticles was assayed by two approximations. When extracts from the nanoparticles were evaluated in cultures of cell lines, no cytotoxic damage was observed at concentrations of less than 10 mg/mL. This demonstrated their biocompatibility. Another experiment using FTIR microspectroscopy evaluated the cytotoxic effect of nanoparticles internalized by endocytosis in cancer cells. The results demonstrated slight damage to the biomacromolecules when the cells were treated with ACP nanoparticles. Both ACP and cHAp nanoparticles were efficiently encapsulated in PLA electrospun matrices, providing functionality and bioactive properties.     

稀土氧化钇改性磷酸钙骨水泥的研究

磷酸钙骨水泥是一种新型的自固化的非陶瓷羟基磷灰石人造骨材料,具有良好的生物相容性、自固化能力、易于塑形、与成骨活性相协调的溶解性能可作为药物、生物活性因子缓释载体等优越的性能。稀土掺杂羟基磷灰石,对羟基磷灰石的合成有促进作用,并且使其具有更稳定的性质。钇的加入有助于羟基磷灰石生物活性的提高。笔者利用钇掺改善羟基磷灰石生物活性作为探讨。其采用氧化钇对磷酸钙骨水泥进行改性研究,考察磷酸钙骨水泥凝结时间、可注射性和孔隙率等基本性能。采用X射线衍射分析骨水泥粉末在水化过程中的变化及其最终产物。采用电镜观察产物的微结构和表面形貌。研究结果表明:钇加入没有影响磷酸钙骨水泥的水化,并且随着钇含量的增加磷酸钙骨水泥的固化体凝结时间逐渐延长,其中氧化钇含量在5%时凝结时间最短;骨水泥浆体的可注射性变大,其中氧化钇含量在1.5%时可注射性最大(壳聚糖溶液)。磷酸钙骨水泥水化最终产物为片状或棒状的羟基磷灰石,其结构呈紧密联系,但表面有较多的孔隙,且随着钇含量的增加孔隙率有增加的趋势。     

A simple pathway in preparation of controlled porosity of biphasic calcium phosphate scaffold for dentin regeneration

A simple pathway in preparation of biphasic calcium phosphate scaffold of hydroxyapatite/beta-tricalcium phosphate with controlled pore size, shape and porosity using phosphoric acid and calcium carbonate was successfully developed. Microporosity was controlled by adjusting temperature and soaking time of the sintering process while macroporosity was obtained through addition of polyethylene spherical particles. The advantage of this method is that a highly pure biphasic calcium phosphate scaffold consisting of hydroxyapatite/beta-tricalcium phosphate in a controlled ratio of 20/80 with a mean pore size of 300 μm and 65% porosity can be produced. These properties of scaffold are of high potential for use in dentin regeneration.     

Formation mechanism of nano-sized hydroxyapatite powders through spray pyrolysis of a calcium phosphate solution containing polyethylene glycol

Nano-sized hydroxyapatite powders were synthesized by spray pyrolysis of a calcium phosphate solution containing polyethylene glycol (PEG) and a subsequent dewaxing process. Calcium phosphate solutions (Ca/P ratio of 1.67) were prepared by dissolving calcium nitrate tetrahydrate and diammonium hydrogen phosphate in deionized water with and without PEG and subsequently adding nitric acid. When the calcium phosphate solution was sprayed at 1100 °C at a carrier gas flow rate of 40 L/min, micron-sized hollow hydroxyapatite particles with dense or collapsed shells were obtained. However, when the calcium phosphate solution containing PEG was sprayed under the same conditions, micron-sized porous hydroxyapatite particles consisting of loosely packed hydroxyapatite crystals containing randomly placed carbons were obtained. When these hydroxyapatite particles were dewaxed at 650 °C for 3 h, they were completely disintegrated into nano-sized hydroxyapatite particles, whereas the micron-sized hollow hydroxyapatite particles without carbons remained intact. After sintering at 1100 °C for 3 h, the relative densities of hydroxyapatite disks made from micron- and nano-sized powders were 78.5 ± 1.7% and 99.8 ± 0.3%, respectively. The practical implication of these results is that highly sinterable nano-sized hydroxyapatite powders can be synthesized through spray pyrolysis of a calcium phosphate solution containing PEG.     

Renal lithiasis and nutrition

Renal lithiasis is a multifactorial disease. An important number of etiologic factors can be adequately modified trough diet, since it must be considered that the urine composition is directly related to diet. In fact, the change of inappropriate habitual diet patterns should be the main measure to prevent kidney stones. In this paper, the relation between different dietary factors (liquid intake, pH, calcium, phosphate, oxalate, citrate, phytate, urate and vitamins) and each type of renal stone (calcium oxalate monohydrate papillary, calcium oxalate monohydrate unattached, calcium oxalate dihydrate, calcium oxalate dihydrate/hydroxyapatite, hydroxyapatite, struvite infectious, brushite, uric acid, calcium oxalate/uric acid and cystine) is discussed.     

Novel crosslinkable polyester resin–based composites as injectable bioactive scaffolds

In this study new composite materials obtained by crosslinking two polyester resins were investigated. The solid composite material and the scaffolds with varied porosity were obtained in the presence of a foaming system consisted of calcium carbonate/citric acid mixture. It was found that the presence of citric acid solution influenced rheological behavior of liquid formulations as well as morphology and mechanical properties of cured materials. SEM observations and analysis by energy-dispersive X-ray dispersive spectroscopy confirmed the presence of hydroxyapatite formed at the scaffolds surfaces in phosphate buffer solution. The MTS cytotoxicity assay was carried out for extracts from selected composite materials using the human osteosarcoma cells (SaOS-2).     

Kinetics of Hydroxyapatite Formation at Low Temperature

The influence of temperature on the kinetics of formation of calcium-deficient hydroxyapatite by an acid-base reaction has been determined. Calcium-deficient hydroxyapatite is compositionally similar to bone apatite. Reactants used in this study were tetracalcium phosphate, a calcium phosphate more basic than hydroxyapatite, and dicalcium phosphate, which is more acidic than hydroxyapatite. The kinetics of hydroxyapatite formation are initially controlled by the surface areas of the reactants; however, eventually the rate of hydroxyapatite formation becomes diffusionally controlled. The origin of diffusion control appears to be associated with the epitaxial formation of hydroxyapatite on the surface of the dicalcium phosphate reactant. The microstructure of hydroxyapatite formed at 5°, 15°, and 25°C were generally similar and are characterized by the formation of a porous acicular product which covers the surfaces of the reactants. The microstructure of the hydroxyapatite formed at 38°C was distinct from this and exhibited a pseudomorphic relationship with the dicalcium phosphate reactant. Seeding with hydroxyapatite accelerated the initial reaction but did not appear to have major long-term effects on the fractional degree of reaction or on microstructural development. Reaction was also accelerated in a neutral salt solution of high ionic strength.     

Interaction of calcium phosphates with calcium oxide or calcium hydroxide during the “soft” mechanochemical synthesis of hydroxyapatite

In the present work, the formation kinetics of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ during ball milling of mixtures of calcium phosphates with calcium oxide or calcium hydroxide was studied. The conversion degrees of reaction mixtures containing calcium dihydrogenphosphate/dicalcium phosphate/tricalcium phosphate/calcium pyrophosphate and calcium oxide/calcium hydroxide were determined for different milling times. The formation kinetic data were analyzed together with the Gibbs free energies of the corresponding reactions. It was found that the kinetic factors dominate at the initial formation stage of hydroxyapatite due to the acid-base interactions during the “soft” mechanochemical synthesis. A technologically attractive synthesis route of Ca₁₀(PO₄)₆(OH)₂ was suggested based on the “soft” mechanochemical synthesis via reactions between СаНРО₄ and СаО or Са(ОН)₂.     

Influence of precursor characteristics on properties of porous calcium phosphate-titanium dioxide composite bioceramics

Highly porous (macroporosity 76–90%) bioceramics containing interconnected pores (>100 μm) with compressive strength between 0.54 and 0.32 MPa were prepared by polyurethane foam replica method. Effect of following variables, i.e., calcium phosphate/anatase ratio (30/70, 50/50, 70/30 wt%) in the ceramic slurry, anatase particle size (15 nm, 180 nm), Ca/P molar ratio of calcium phosphate (1.67 and 1.50 for hydroxyapatite and apatitic-tricalcium phosphate (ap-TCP), respectively), on the bioceramics properties was investigated. Bioceramics prepared using anatase and hydroxyapatite consisted of three high-temperature crystalline phases - β-tricalcium phosphate (β-TCP), rutile and CaTiO₃. In case of anatase and ap-TCP, two phases (β-TCP and rutile) were obtained. Interaction of anatase and hydroxyapatite during sintering caused formation of CaTiO₃ at β-TCP and rutile grain boundaries thus contributing to a denser grain packing. Combination of ap-TCP and nanosized anatase facilitated decrease of grain sizes. Correlation was found between compressive strength and calcium phosphate precursor in the ceramic slurry.