Calcium phosphate bioceramics prepared from wet chemically precipitated powders

In this work calcium phosphates were synthesized by modified wet chemical precipitation route. Contrary to the conventional chemical precipitation route calcium hydroxide was homogenized with planetary mill. Milling calcium oxide and water in planetary ball mill as a first step of synthesis provides a highly dispersed calcium hydroxide suspension. The aim of this work was to study the influence of main processing parameters of wet chemical precipitation synthesis product and to control the morphology, phase and functional group composition and, consequently, thermal stability and microstructure of calcium phosphate bioceramics after thermal treatment. The results showed that it is possible to obtain calcium phosphates with different and reproducible phase compositions after thermal processing (hydroxyapatite [HAp], β-tricalcium phosphate [β-TCP] and HAp/β-TCP) by modified wet-chemical precipitation route. The β-TCP phase content in sintered bioceramics samples is found to be highly dependent on the changes in technological parameters and it can be controlled with ending pH, synthesis temperature and thermal treatment. Pure, crystalline and highly thermally stable (up to 1300°C) HAp bioceramics with homogenous grainy microstructure, grain size up to 200–250 nm and high open porosity can be successfully obtained by powder synthesized at elevated synthesis temperature of 70°C and stabilizing ending pH at 9

Development of porous ceramics by lycopodium using uniaxial pressing and sintering

In this work microporous hydroxyapatite (HAp) ceramics were fabricated using lycopodium as a porosifier. The samples were produced by uniaxial pressing and then heating at high temperatures, 1100°C and 1200°C, to burn-out porogens and sintering. The obtained samples had porosity over the variable range of 12 to 45% with different pore size ranging from 0.2 to 25 µm. Chemical and physical characterization was determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and bending strength measurements. The bending strength of the prepared samples was in the range of 1.97–21.81 MPa

Difference in cytological findings of healthy and conjunctivitis/keratoconjunctivitis affected canine eyes between variably experienced evaluators

Background and Aim: Cytology investigations are a frequent part of ophthalmological examination. We aimed to assess whether the cytological findings of healthy and conjunctivitis/keratoconjunctivitis samples differed based on the evaluator's experience. Materials and Methods: A study evaluated healthy eyes (n = 40) and eyes affected with keratoconjunctivitis and/ or conjunctivitis (n = 28) in dogs. An ophthalmological examination was performed before sampling the eyes using a sterile cotton swab. An evaluator with theoretical experience and one with undergone clinical pathology residency training performed cytology blinded to the clinical findings. Results: In the healthy eyes group, the agreement between the evaluators for cellularity was nonexistent, while that for cell preservation and mucus content was fair. In the affected eyes group, the agreement for cellularity and mucus content was moderate, while that for cell preservation was fair. The inadequate sample rate differed significantly between the two evaluators in the healthy eyes group (p = 0.006) but not in the affected eyes group (p = 0.083). Bacterial presence was detected by both evaluators, and the findings did not differ statistically from the bacteriology results (p = 0.05). Significant variations were noted in the differential cell count; the mean count of the superficial epithelial cells and goblet cells of the healthy eyes group (p < 0.05) and that of the basal/intermediate cells and neutrophils of the affected eyes (p < 0.05) showed significant differences. Conclusion: The evaluator's experience significantly affected the differential cell count in both the healthy and affected eyes groups. Neutrophil degeneration was not observed by the less experienced evaluator, whereas bacteria were detected equally well by both the evaluators

Sintered glass-ceramic matrix composites made from Latvian silicate wastes

Powder technology and sintering were used to fabricate glass-ceramic matrix composites from Latvian industrial wastes and alumina platelets reinforcement. The optimization of the sintering behaviour of glass-ceramic compositions containing clay and alumina platelets was carried out. Highly crystalline and dense products (> 90 % theoretical density) were fabricated by sintering at temperatures in the range 1040 to 1060 °C, depending on composition. Addition of waste glass to influence the sintering temperature and sintering interval was also investigated. Composites showed higher fracture strength (up to 97 MPa) and hardness than unreinforced glass-ceramics. The "best" composition in terms of density and mechanical properties contained 20 wt% alumina platelets. The matrix exhibited a microstructure composed mainly of elongated crystals of pyroxene type in a residual glassy matrix. These composites are candidates for applications as building materials, such as floor and wall tiles, and for manufacturing machine elements and parts

Early morphofunctional response of contact tissue after intraosal implantation in rabbit jaw of pure synthetic hydroxyapatite (HAp) bioceramic materials and HAp saturated with lidocaine

PURPOSE: The aim of this study was to evaluate early morphofunctional response of contact tissue to pure and saturated with lidocaine porous synthetic HAp ceramic implants inserted in holes of rabbit upper jaw. MATERIALS AND METHODS: Pure and saturated with lidocaine cylinders of porous HAp ceramics produced at Biomaterials R&D Laboratory of Riga Technical University were inserted into edentulous part of the upper jaw of 12 New Zealand male rabbits. After two weeks, blocks of soft tissue and bone were taken out. The sections done with EXACT Grunding system and from paraffin blocks were stained with haematoxylin/eosin and by use of biotin-streptavidin immunohistochemistry for transforming growth factor beta1 (TGFbeta1), fibroblast growth factor receptor 1 (FGFR1), interleukin 10 (IL10). Apoptosis was detected by TUNEL method. RESULTS: TGFbeta1 was equally expressed in the bone around HAp implants saturated with lidocaine and without lidocaine, while control sections did not show any expression of TGFbeta. In contacting bone tissue to pure HAp and HAp saturated with lidocaine as well in controls rich expression of FGFR1 was observed. In soft tissue of experimental samples also rich expression of FGFR1 was observed, although it was weak in control samples. IL10 had rich expression in all samples. The mean number of apoptotic cells was higher in samples with pure HAp, slightly decreased in samples HAp with lidocaine and significantly lower in controls. CONCLUSIONS: The expression of TGF beta1 confirms osteoinductive activity of HAp. Contact soft tissue to HAp showed rich FGFR1 expression, and weak in controls suggesting higher plasticity of connective tissue to implants in comparison with supportive tissue. Slightly lower apoptosis in samples of HAp with lidocaine gives evidence of indistinct influence of saturated with lidocaine HAp implants on development of programmed cell death.publishersversionPeer reviewe

Complex multilayer carbon structures for green energetics

The authors greatly acknowledge the IMIS2 project of the National Reform Programme of Latvia for financial support. The publication costs of this article were covered by the Estonian Academy of Sciences and the University of Tartu.We investigated a promising material for hydrogen storage and sensing. The material was obtained by exfoliating recycled graphite waste and simultaneously modifying the product with metal impurities (Bi, V, Cu). As a result, graphene sheet stack (GSS) powder was obtained. The material was further processed by hydrothermal annealing and reduction. Raman spectra of the GSS materials are provided to show the presence of graphene-like structures and defects in the exfoliated material. The synthesized graphene material has good semiconductor properties with a low electrical resistance for hydrogen sensing applications.Tartu Ülikool, Eesti Teaduste Akadeemia, Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

An In Vitro and In Vivo Study on the Intensity of Adhesion and Colonization by Staphylococcus epidermidis and Pseudomonas aeruginosa on Originally Synthesized Biomaterials With Different Chemical Composition and Modified Surfaces and Their Effect on Expression of TNF-alpha, beta-Defensin 2 and IL-10 in Tissues

publishersversionPeer reviewe

Calcified Algae for Tissue Engineering.

This book presents the latest advances in marine structures and related biomaterials for applications in both soft- and hard-tissue engineering, as well as controlled drug delivery