Hydroxyapatite

Renal lithiasis is a multifactorial disease. An important number of etiologic factors can be adequately modified through 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.

We report the preparation of hydroxyapatite in powdered form by aqueous reaction of calcium nitrate or hydroxide with phosphate ion at room temperature. With a slow maturation step of 48 h avoiding heat, the resulting products show large specific surface areas above 150 m2/g. The specific surface areas also depend on stirring speed with a maximum observed with gentle mixing. Ageing causes

Production of nanostructured materials, similar to the complex structure of nano-calcite of hard tissues, egg shell, teeth and bone, are an attractive field of research. Calcium phosphates with clinical applications, such as hydroxyapatite (HA) (Ca 10 (PO4) 6 (OH) 2) have been widely used in regeneration of bone and fabrication of medical implants, mainly due to the chemical composition and structure similarity between HA and the mineral part of bones and teeth, and also as gene and drug delivery is used. High surface area of HA make it useful for drug release. Moreover, it has antibacterial property and potential applications in rapid microbial detection, treatment of heavy metals from aqueous solutions. Biological synthesis has been attracted more attention for compatibility to human safety.

Hydroxyapatite (HA) - Ca(10)(PO(4))(6)(OH)(2) is a basic inorganic model component of hard biological tissues, such as bones and teeth. The significant property of HA is its ability to exchange Ca(2+) ions, which influences crystallinity, physico-chemical and biological properties of modified hydroxyapatite materials. In this work, FTIR, Raman spectroscopy, XRD. SEM and EDS techniques were used to determine thermal stability, chemical and phase composition of Mn containing hydroxyapatite (MnHA). Described methods confirmed thermal decomposition and phase transformation of MnHA to alpha TCP, beta TCP and formation of Mn(3)O(4) depending on sintering temperature and manganese content. In vitro biological evaluation of Mn-modified HA ceramics was also performed using human osteoblast cells. (C) 2010 Elsevier B.V. All rights reserved.

Strains traditionally identified as Proteus vulgaris formed three biogroups. Biogroup 1, characterized by negative reactions for indole production, salicin fermentation and aesculin hydrolysis, is now known as Proteus penneri. Biogroup 2, characterized by positive reactions for indole, salicin and aesculin, was shown by DNA hybridization (hydroxyapatite method) to be a genetic species separate from biogroup 1 and from biogroup 3 which is positive for indole production and negative for salicin and aesculin. In this study, 52 strains were examined, of which 36 strains were Proteus vulgaris biogroup 3, which included the current type strain of the species P. vulgaris (ATCC 29905T), and compared to seven strains of Proteus vulgaris biogroup 2 and nine type strains of other species in the genera Proteus, Providencia and Morganella. By DNA hybridization, these 36 strains were separated into four distinct groups, designated as Proteus genomospecies 3, 4, 5 and 6. DNAs within each separate ...

The influence of ionic substituents in calcium phosphates intended for bone and tooth replacement biomedical applications is an important research topic, owing to the essential roles played by trace elements in biological processes. The present study investigates the mechanical and biological evaluation of ionic doped hydroxyapatite/β-tricalcium phosphate mixtures which have been prepared by a simple aqueous precipitation method. Heat treating the resultant calcium phosphates in a carbonated atmosphere led to the formation of ionic doped carbonated hydroxyapatite/β-tricalcium phosphate mixtures containing the essential ions of biological apatite. The structural analysis determined by Rietveld refinement confirmed the presence of hydroxyapatite as the main phase, together with a considerable amount of β-tricalcium phosphate. Such phase assemblage is essentially due to the influence of substituted ions during synthesis. The results from mechanical tests proved that carbonate substitutions are detrimental for the mechanical properties of apatite-based ceramics. In vitro proliferation assays of osteoblastic-like cells (MC3T3-E1 cell line) to powders revealed that carbonate incorporation can either delay or accelerate MC3T3 proliferation, although reaching the same proliferation levels as control cells after 2 weeks in culture. Further, the powders enable pre-osteoblastic differentiation in a similar manner to control cells, as indirectly measured by ALP activity and Type-I collagen medium secretion.

The aim of this study was to characterize and compare various titanium (Ti) and hydroxyapatite (HA) coatings on Ti6Al4V, in view of their application on noncemented orthopedic implants. Two innovative vacuum plasma sprayed (VPS) coatings, the first of ultrahigh rough and dense Ti (PG60, Ra=74 microm) and the second of ultrahigh rough and dense Ti coated with HA (HPG60, Ra=52 microm), have been developed, and the response of osteoblast-like cells (MG-63) seeded on these new coatings was evaluated in comparison to: a low roughness and sandblasted (Ti/SA, Ra=4 microm) Ti6Al4V surface; Ti medium (TI01, Ra=18 microm), and high (TI60, Ra=40 microm) roughness VPS coatings; and the relative Ti plus HA duplex coatings (HT01, Ra=12 microm and HT60, Ra=36 microm respectively), also obtained by VPS. PG60 coating presented no open porosity, making it dense and potentially intrinsically stronger. Cell adhesion and proliferation on PG60 was similar to those of the smoothest one (Ti/SA) and adhesion on ultrahigh roughness was lower than the medium- and high-roughness coatings, whereas cell proliferation on PG60 was lower than TI60. The HA coating determined significant increases in cell proliferation at medium and high roughness levels when compared to the relative Ti coating, but not compared to the ultrahigh one; all HA-coated surfaces showed a decrease in alkaline phosphatase activity and collagen I production. Surface morphology and the HA coating strongly affected cell behavior. However, ultrahigh values of roughness are not correctly seen by cells, and the presence of HA has no improving effects.

The dispersion of colloidal ceramic particles in an aqueous media using a charged polymer has been investigated extensively. Most often, such a dispersion is obtained by an electrosteric mechanism. The stabilizing forces that result from electrical double layer repulsion and/or steric interaction must be sufficiently large in magnitude to provide an energy barrier against aggregation. Several factors, such as pH, temperature and ionic strength, nature, structure and molecular weight of the polyelectrolyte and its degree of dissociation can affect the respective contribution of electrostatic and steric interactions. In this study we applied silver nanoparticles prepared by reduction method with modifications. The hydroxyapatite was obtained from pork bone sludge. Polymer system contained poly(acrylic acid) and poly(ethylene glycol). The effects of dispersant structure on particle stabilization were investigated through properties of the suspensions. Viscosity and sedimentation height measurements indicated that addition of the dispersants improve particle stabilization. A dispersants were characterized using Scanning electron microscopy (SEM) with BSE detector (Back Scaterred Electrons), X-ray diffraction (XRD) and pH determination.

The properties of porous hydroxyapatite (HA) bioceramic produced by heat treatment (annealing) of bovine bone were evaluated over temperatures between 400 °C and 1200 °C. The annealed body was characterized by thermal analysis (thermogravimetric analysis (TG)/differential thermal analysis (DTA)), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The XRD results showed that the annealing process enhanced the crystallinity of HA phase in the bone matrix particularly when annealed above 700 °C. There was no secondary phase formation in bones annealed between 600 °C and 1000 °C. However, decomposition of HA to β-tricalcium phosphate (TCP) was observed for samples heat-treated at 1100 °C and 1200 °C. The FTIR spectra and the TG/DTA thermogram of as-received bovine bone indicated the presence of organic compounds, which upon annealing at temperatures above 600 °C was completely removed from the matrices. Bovine bone annealed between 800 °C and 1000 °C revealed the characteristics of a natural bone with the interconnecting pore network being retained in the structure.

http://www.sciencedirect.com/science/article/pii/S0272884206001581

A composite can be defined as a material having two or more chemically distinct phases,
which at the microscopic scale are separated by a distinct interface. A composite have light
weight, high strength to weight ratio and stiffness properties and replaces the conventional
materials. Composites are finding applications in many fields ranging from construction to
automotive industry and today widely in biomedical field as well. Hydroxyapatite (HAp) is a
suitable ceramic material for tissue repair and replacement. In this study, ceramic composites
comprising of synthetic HAp reinforced with Polycarbonate (PC) thermoplastic polymer are
fabricated and tested to assess mechanical behaviour of ceramic composite. The materials
may serve the purpose in biomedical engineering in respect to repair and replacement of
fractured bone with artificial bone materials. Many implant materials has been made in the
last three decades of metals, alloys, ceramics and polymers etc. Most metals and ceramics are
much stiffer than bone tissue, which can result in mechanical mismatch (i.e. “stress
shielding”) between the implant and the adjacent bone tissue. Because metals are too stiff in
addition to their other biocompatibility problems, ceramics are too brittle and polymers are
too flexible and weak to meet the mechanical strength while polymers are popular due to
their low density, good mechanical strength, and easy formability however, low stiffness,
high wear rate and low hardness limit their use in various demanding applications. To
overcome these difficulties polymeric bone implants may be used. In this present work, HAp
has been synthesized by wet chemical precipitation route. HAp particulates incorporated into
polymer matrix through a series of processing stages involving melt compounding,
granulating and micro-injection molding. The samples were characterized by X-ray
diffraction (XRD), Fourier transform infrared (FT-IR) and Scanning electron microscopy
(SEM). The mechanical properties such as tensile, compression, flexural, impact and
hardness have been assessed for the composite varying HAp volume percentage in PC
polymer. The aim is to produce a material that has similar mechanical properties to that
of bone in order to achieve mechanical compatibility in the human body

Bioactive ceramics such as hydroxyapatite (HA) can mimic the organic structure of human bone. HA was successfully synthesized from animal bones, corals, and eggshells which have been studied for bone repairing treatment and as implant coatings. This study aims to synthesize nanorod HA from cockle shells via two routes: calcination and the hydrothermal method. The raw cockle shells were converted to calcite by calcination method at 450 degrees C (CS450) and 800 degrees C (CS800) for 2 hrs. The calcite calcium carbonate samples were reacted with diammonium hydrogen phosphate and hydrothermally treated at 110 degrees C. The pH of the solution was kept at 10.5 throughout the synthesis step by adding drops of ammonia. Product obtained was labelled as HA450 and HA800 containing HA powder. Presence of calcite phase in the raw cockle shells was characterized by utilizing Thermogravimetric analysis (TGA), X­ray Diffraction (XRD) and Fourier transforms infrared spectrophotometer (FTIR) analyses and morphologically analyzed by Field emission scanning electron microscopy (FESEM). The best result was obtained from the HA800 sample where nanoparticle with rod­like shape was observed (aspect ratio = 7) while needle­like particle was seen in HA450 sample (aspect ratio = 20). High purity HA was developed in HA800 sample while HA450 showed small presence of calcite phase. In vitro bioactivity test of HA powder samples incubated simulated body fluid (SBF) for 1, 3, 8, 15 and 21 days showed high bioactivity in both samples by forming apatite agglomerate on the surfaces. Higher microhardness strength was observed in HA800 compared to HA450, CS450 and CS800 sintered pellet samples.

Bioactive glasses have attracted considerable interest in recent years, due to their technological application, especially in biomaterials research. Differential scanning calorimetry (DSC) has been used in the study of the crystallization mechanism in the SiO2–Na2O–CaO–P2O5 glass system, as a function of particle size. The curve of the bulk glass presents a slightly asymmetric crystallization peak that could be deconvoluted into two separate peaks, their separation being followed in the form of powder glasses. Also, a shift of the crystallization peaks to lower temperatures was observed with the decrease of the particle size. FTIR studies – that are confirmed by XRD measurements – proved that the different peaks could be attributed to different crystallization mechanisms. Moreover, it is presented the bioactive behavior of the specific glass as a function of particle size. The study of bioactivity is performed through the process of its immersion in simulated human blood plasma (simulated body fluid, SBF) and the subsequent examination of the development of carbonate-containing hydroxyapatite layer on the surface of the particles. The bioactive response is improved with the increase of the particle size of powders up to 80 μm and remains almost unchanged for further increase, following the specific surface to volume ratio decrease.