Liga Stipniece

Synthesis of Strontium Substituted Hydroxyapatite through Different Precipitation Routes

The aim of this work was to evaluate the effect of precursor materials used in the synthesis on the Sr incorporation levels into the hydroxyapatite (HAp) lattice and to characterize the synthesis products. HAp powders containing various amounts of Sr were synthesized through three different precipitation routes. In all cases, the as-synthesized products were found to be pure HAp. However, atomic absorption spectrometry analysis showed that by reacting orthophosphoric acid with calcium hydroxide and strontium hydroxide, as well as by reacting diammonium hydrogen phosphate with calcium nitrate tetrahydrate and strontium nitrate a significant proportion of the Sr added, did not substitute into the HAp lattice. X-ray diffraction analysis revealed that the effect of substituting relatively high amounts (up to 3.69 ± 0.37 wt.%) of Sr into the HAp lattice was to decrease the cristallinity. Brunauer-Emmett-Teller (nitrogen absorption) analysis showed that the incorporation of Sr reduced particle sizes of the precipitated HAp products. Contrary, scanning electron microscopy revealed that the incorporation of Sr increased length of the precipitated needle-like particles.

Effect of Mg Content on Thermal Stability of β-Tricalcium Phosphate Ceramics

β-Tricalcium phosphate bioceramics with small, close to bone-like amounts of Mg were obtained by modified precipitation method and following sintering. The effect of small amounts of Mg on the thermal stability, microstructure and sintering behavior of β-tricalcium phosphate bioceramics was evaluated. Addition of small amounts of Mg, can induce a remarkable effect on the physic-chemical properties of β-TCP and therefore the chemical composition of the starting materials should be controlled.

Mechanical Properties and Biocompatibility of a Biomaterial Based on Deproteinized Hydroxyapatite and Endodentine Cement

Abstract Hydroxyapatite is used for bone reconstruction, in order to improve its mechanical properties different substances can be added. In our study new biomaterial is created from deproteinised hydroxyaptite and endodentic cement, its mechanical properties were tested. Material was implanted subcutaneous in rats, then histological and biocompatability tests were performed. Results indicate that stuff has good mechanical properties, short setting time and gradual resorption creating porosity and ability to integrate in bone.

Evaluation of Sr- and/or Mg-Containing Hydroxyapatite Behavior in Simulated Body Fluid

The main goal of this study was to evaluate the behavior of Sr- and/or Mg-containing hydroxyapatite (HAp) bioceramics in simulated body fluid (SBF). Sr-and/or Mg-containing HAp powders were synthesized by modified wet chemical precipitation method. Sr-and/or Mg-containing HAp bioceramics were prepared by uniaxial pressing of the precipitated powders and subsequent sintering at 1100 °C for 1 h. The synthesis products were characterized in terms of chemical, phase and molecular composition. Influence of the substitutions on thermal stability, morphology and microstructure of the HAp products were evaluated. Results suggest that incorporation of Sr (up to 1.45 wt.%) in HAp structure induced an increasing of particle sizes, but incorporation of Mg (up to 1.05 wt.%) led to a reduction of particle sizes of the HAp powders. The ability to simultaneously release bioactive ions and the apatite-formation ability of the Sr-and/or Mg-containing HAp bioceramics were evaluated through immersing the samples in SBF for different time periods. Ca ions release and apatite-formation ability on the surfaces of the Sr-and/or Mg-containing HAp bioceramics in SBF depends on Sr and/or Mg concentration in the samples.

The Influence of Biogenic and Synthetic Starting Materials on the Properties of Porous Hydroxyapatite Bioceramics

The aim of this study was to investigate the influence of biogenic and synthetic starting materials on properties of porous hydroxyapatite (HAp) bioceramics. HAp powders were synthesized by modified precipitation method using biogenic calcium carbonates (ostrich (Struthio camelus) egg shells, hen (Gallus gallus domesticus) egg shells, snail (Viviparus contectus) shells) and synthetic calcium oxides (Sigma-Aldrich and Fluka). Specific surface area, molecular structure and morphology of obtained powders were determined. As-synthesized HAp powders had a varied specific surface area with a wide range from 83 to 150 m2g-1 depending on CaO source. Porous bodies of HAp were prepared by in situ viscous mass foaming with NH4HCO3 as pore forming agent. Foamed and dried green bodies were sintered at 1100 °C. The obtained bioceramics were investigated using Archimedes method, field emission scanning electron microscopy and Brunauer-Emmett-Teller method. There are considerable differences between porous HAp bioceramics structures prepared from different sources of CaO. The choice of starting material substantially affects the macro-and microstructure of prepared porous bioceramics.

Incorporation of Magnesium Ions into Synthetic Hydroxyapatite: Synthesis and Characterization

The objective of this work is to synthesize pure and Mg-substituted hydroxyapatite (HAp) powders with different MgO content in synthesis media (in the wide range of 0.1-10.0 wt% in respect to Ca), and to study the influence of Mg2+ ions substitution on the physicochemical properties of HAp materials. In this work HAp and magnesium-substituted hydroxyapatite (Mg-HAp) were synthesized by modified wet chemical precipitation of homogenous suspension of Mg(OH)2/Ca(OH)2 and H3PO4 solution. Systematic investigation on as-synthesized and sintered Mg-HAp and HAp samples shows that the incorporation of MgO promotes decomposition of HAp to β-tricalcium phosphate (β-TCP) and significantly modified its microstructure. The effect and evidence of incorporation of Mg2+ ions into HAp structure is discussed.

Electrophoretic Deposition of TiO2 Nanoparticles on Dense TiO2-x Ceramic Electrodes

TiO2 nanoparticles were electrophoretically deposited on the dense TiO2-x ceramic electrodes from suspension containing TiO2 nanoparticles, isopropanol as a solvent and triethanolamine as dispersant. The effect of deposition parameters including deposition voltage (10 to 60 V) and deposition time (10 to 40 min) on the microstructure and deposition yield was examined. It was found that the thickness of coating increased with increasing deposition time and deposition voltage. However, it affected the quality of obtained coating e.g. cracks and holes were observed. Optimizing deposition parameters homogeneous coating with smooth microstructure and limited surface damage can be obtained. Thermal treatment of the coating in the temperature range from 700 to 1100 °C causes anatase to rutile phase transformation. Crack formation was noted during sintering due to the phase transformation and thermal stresses.

Encapsulation of Strontium Ranelate in Poly(Lactic Acid) Matrix

Osteoporosis is a disease characterized with reduced density and quality of bone. Novel treatment strategies have been developed with the aim to inhibit excessive bone resorption and to increase bone formation. Strontium ranelate (SrRan), a novel orally active agent consisting of two atoms of stable strontium and the organic moiety ranelic acid, has proven drug ability to increase not only the bone mass but also mechanical properties. Despite the advantages it has been shown that systemic administration of SrRan can cause such side effects as diarrhea, hypersensitivity and myocardial infarction. Microencapsulation of SrRan could overcome the possible side effects from the systemic drug use as well as to increase its efficiency by local delivery of drug right to the affected bone site. Thus in the current research an attempt was made to prepare and characterize poly (lactic acid)/srontium ranelate microcapsules and to evaluate the drug interaction with the polymer during the microparticle formation.

Change of Biomechanical Parameters in the Lower Jaws of Rabbits with Experimental Osteoporosis after Implantation of Calcium-Phosphate Bioceramic Material in the Greater Trochanter Region

Investigation of biomechanical properties of the rabbit bone tissue from a corner of the lower jaw was done. Experimental osteoporosis was induced by ovariectomy and following injections of methylprednisolone. The defects in the greater trochanter region was created and filled with granules of a hydroxyapatite and tricalcium phosphate (HAP/TCP 30/70) or HAP/TCP 30/70 together with 5% strontium ranelate. After 3 month animals were euthanased, squared samples have been cut out from a corner of the lower jaw and tested on a bend. Results of research show, that the corner of a lower jaw in rabbit becomes more rigid after filling of defects in the greater trochanter region with granules of a hydroxyapatite and tricalcium phosphate (HAP/TCP 30/70) or granules together with strontium ranelate. The ultimate strain for the bone tissue in the 2nd and 3rd group is less, than for control group. Thus, local uses calcium – phosphatic bioceramic material around the greater trochanter region improves biomechanical parameters of a bone tissue in the lower jaw of animals.

Sr- and/or Mg-Containing Nanocrystalline Hydroxyapatite: Study from Synthesis to Calcined Products

In this work, nanocrystalline hydroxyapatite (HAp) powders were synthesized through wet precipitation method by adjusting the reaction temperature between 0 °C and 5 °C. The influence of biologically active Mg and Sr addition on HAp crystalline structure and thermal behavior was assessed. In all synthesis, nanocrystalline and/or amorphous HAp was found to be the major phase, and was accompanied by Ca(OH)2 as the minor phase. Results suggested that Sr and Mg have an impending effect on nucleation, crystallization and thermal stability of HAp. The addition of Sr or Mg promoted deviation from stoichiometry and formation of amorphous components, which affected thermal stability and sintering behavior of the synthesis products.