Anna Ślósarczyk

The FTIR spectroscopy and QXRD studies of calcium phosphate based materials produced from the powder precursors with different CaP ratios

Abstract Six precipitates of calcium phosphates with Ca P molar ratios in the range of 1.502–1.717 have been prepared by the wet method. After shaping and sintering at 1250 °C the phase composition of the obtained materials was examined by QXRD and FTIR spectroscopy methods.

Hot pressed hydroxyapatite–carbon fibre composites

Abstract Composite samples were obtained from hydroxyapatite powder and carbon fibres by hot pressing at 1100°C and 25 MPa for 15 min in argon atmosphere. Two types of cut carbon fibres produced in a carbonisation process of polyacrylonitrile (PAN) precursor were used both in non-coated or coated form. The coatings of calcium phosphate were applied by sol–gel technique. The highly sintered composite with the best strength properties was obtained from coated carbon fibres with basic character of the surface. The existence of hydroxyl groups on fibre surface makes possible formation of bonds with the calcium phosphate layer formed as a result of polycondensation following the sol–gel procedure.

Ceramic materials on the basis of hydroxyapatite and tricalcium phosphate

Abstract Studies on mono-, bi-, or triphase ceramic materials consisting of hydroxyapatite (HAp), β tricalcium phosphate (β-TCP), α tricalcium phosphate (α-TCP) and CaO are reported. The synthesis of powder precursors were carried out at Ca/P molar ratios below, equal or over 1.67 and at pH of reaction environment equal 5, 6 or 11. The microstructure, phase composition and density of the uniaxially or isostatically compacted samples after sintering at 1250°C were analysed using SEM, QXRD, FTIR, EDS and porosymetric techniques. Elastic properties of the investigated materials were determined by the ultrasonic method. The relationship between the precipitation conditions and the properties of final calcium phosphate ceramics was confirmed.

Covalent coating of hydroxyapatite by keratin stabilizes gentamicin release

A novel hybrid hydroxyapatite (HAP) matrix, covalently coated with rarely applied, hardly degradable keratin and effectively modified by gentamicin immobilized in mixed-type mode (via interactions of diverse strength), was created. This hybrid showed a remarkably high drug immobilization yield and the most sustainable antibiotic release among all tested composites. It was also able to inhibit bacterial growth, both in surrounding liquid and on matrix surface, much longer (for at least 121 days of experiment) than analogous gelatin-modified and nonmodified matrices. Gentamicin-keratin-coated-HAP granules were nontoxic to human osteoblasts and enabled their proliferation with a rate similar as noncoated HAP. Presence of keratin on HAP granules seemed to slightly enhance the osteoblast proliferation. The results indicate that newly created HAP hybrid with covalently immobilized keratin and gentamicin--nontoxic and osteoblast-friendly--is a promising biomaterial of significantly prolonged antibacterial activity.

Effect of a carbonated HAP/β-glucan composite bone substitute on healing of drilled bone voids in the proximal tibial metaphysis of rabbits.

A novel elastic hydroxyapatite-based composite of high surgical handiness has been developed. Its potential application in orthopedics as a filler of bone defects has been studied. The biomaterial was composed of carbonated hydroxyapatite (CHAP) granules and polysaccharide polymer (β-1,3-glucan). Cylinders of 4mm in diameter and 6mm in length were implanted into bone cavities created in the proximal metaphysis of tibiae of 24 New Zealand white rabbits. 18 sham-operated animals were used as controls. After 1, 3 or 6 months, the rabbits were euthanized, the bones were harvested and subjected to analysis. Radiological images and histological sections revealed integration of implants with bone tissue with no signs of graft rejection. Peripheral quantitative computed tomography (pQCT) indicated the stimulating effect of the biomaterial on bone formation and mineralization. Densitometry (DXA) analysis suggested that biomineralization of bones was preceded by bioresorption and gradual disappearance of porous ceramic granules. The findings suggest that the CHAP-glucan composite material enables regeneration of bone tissue and could serve as a bone defect filler.

Application of β-1,3-glucan in production of ceramics-based elastic composite for bone repair

BackgroundUnsatisfactory surgical handiness is a commonly known disadvantage of implantable granular bioceramics. To overcome this problem, β-1,3-glucan, biotechnologically derived polysaccharide, has been proposed as a joining agent to combine granular ceramics into novel compact and elastic composite. Hydroxyapatite/glucan elastic material was processed and evaluated as a potential bone void filler.MethodologyThe procedure of composite formation was based on gelling properties of glucan. Its properties were studied using X-ray microtomography, SEM-EDS, FTIR spectroscopy, compression test and ultrasonic method. Sorption index was determined in phosphate buffered saline; bioactivity in simulated body fluid; sterility in growth broth and human blood plasma; implantation procedure in dog model.ResultsHAp/glucan composite is sterilizable, flexible and self-adapting to defect shape. It exhibits bioactivity, good surgical handiness, high sorption index and profitable mechanical properties, resembling those of spongy bone. Results of pilot clinical experiment on animal (dog) patients of a local clinic of animal surgery suggested good healing properties of the composite and its transformation into new bone tissue within critical-size defect.ConclusionsThe results obtained in this study confirm that flexible HAp/glucan composite has potential as a bone-substituting material. Promising results of pilot clinical experiment suggest that further in vivo experiments should be performed.

The kinetics of pentoxifylline release in vivo from drug-loaded hydroxyapatite implants

Porous hydroxyapatite implants were evaluated as potential skeletal delivery systems for sustained delivery of drugs. Pentoxifylline (PTX) was employed as a model agent and 50 mg of PTX powder was loaded into hollow cylindrical implants. The kinetics of PTX release from the implants was studied both in vitro, employing phosphate buffer (pH 7.35) at the temperature of 37°C, and in vivo, implanting drug-containing cylinders into rabbit iliac bones. For the sake of comparison rabbits were also administered a single i.v. or i.m. dose of 50 mg PTX. Serum PTX concentration levels were measured using the HPLC method. Results of analyses carried out employing the mercury porosimetry method and the hydrostatic weighing method showed that the investigated biomaterial was characterized by a large number of pores ranging in size from 0.4 to 6 μm and with open and total porosity values of 31.8 and 35.6%, respectively. Studies in vitro revealed typical sigmoid-type drug release patterns with a lag time. After 40 h, the amount of released PTX reached a plateau and equaled 78% of the total amount of drug loaded into an implant. Studies in vivo demonstrated that due to decelerated PTX release from cylinders implanted in rabbit iliac bones, its serum concentration values were maintained at measurable levels almost eight times longer than following the systemic administration of PTX. The serum half-life following PTX administration via implants was significantly higher than the value calculated after systemic administration and equaled 6.3 h. The authors also showed that despite differences in the temporal distribution of PTX concentration values, its bioavailability was similar after i.m. injections and administration via implants. As it follows from the investigations, hydroxyapatite implants manifest positive drug-release patterns both in vitro and in vivo.

Characterization of calcium phosphate coatings doped with Mg, deposited by pulsed laser deposition technique using ArF excimer laser

Calcium phosphate layers were deposited on Ti6Al4V substrates with TiN buffer layers by use of pulsed laser deposition method. With this technique three pressed pellets consisted of tricalcium phosphate (TCP, Ca(3)(PO(4))(2)), hydroxyapatite (HA, Ca(10)(PO(4))(6)(OH)(2)) and hydroxyapatite-doped with magnesium (HA with 4% of Mg and trace amount of (Ca,Mg)(3)(PO(4))(2)) were ablated using ArF excimer laser (lambda=193 nm). The using of different targets enabled to determine the influence of target composition on the nature of deposited layers. The obtained deposits were characterized by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction method (XRD). The obtained Fourier spectras revealed differences in terms of intensity of spectral bands of different layers. The analysis from XRD showed that Mg-doped HA layer has crystalline structure and TCP and HA layers composition is characterized by amorphous nature.

Do novel cement-type biomaterials reveal ion reactivity that affects cell viability in vitro?

Calcium phosphate bioceramics have been studied as bone filler materials for years and have become a component of many commercial products. It is widely known that surface-reactive biomaterials may cause changes in the concentration of crucial ions in the surrounding environment, thereby affecting cell metabolism and viability. The aim of this study was to produce five cement-type biomaterials and characterize their phase composition using X-ray diffraction method, and porosity and pore size distribution using mercury intrusion porosimeter. We then evaluated ion interactions of the novel biomaterials with the surrounding environment (culture medium). A commercially available bone substitute, HydroSet™ (Stryker®), was used as a reference. MTT and NRU cytotoxicity tests were performed to assess the effect of changes in the concentration of crucial ions (calcium, magnesium, phosphate) on osteoblast metabolism and viability in vitro. Our study clearly indicated that various biomaterials demonstrated different ion reactivity and consequently may cause changes in ion concentration in the local environment. Critically low or high values of calcium, magnesium, and phosphate concentrations in the medium exerted cytotoxic effects on the cultured cells. Moreover, we discovered that the chemical composition of the culture medium had a substantial influence on ion interactions with biomaterials.

Bacterial colonisation of bioceramic surfaces

Abstract Hydroxyapatite (HAp – Ca10(PO4)6(OH)2) and tricalcium phosphate (TCP – Ca3(PO4)2) are bioceramic materials of special interest with regards to bone surgery, in particular the repair of bone tissue defects. These materials are highly biocompatible with bone and soft tissue; they are bioactive, osteoconductive and resistant to sterilisation processes. In comparison with other biomaterials, particularly metallic materials, bioceramic surfaces exhibit high resistance to bacterial colonisation. This is currently considered to be one of the most important issues concerning materials used in medicine, due to the fact that bacterial biofilm is difficult to combat or remove and can be responsible for recurrent infections. The aim of the present study was to evaluate bacterial colonisation on the surface of different calcium phosphate based materials.