Papers by Author: Liga Berzina-Cimdina

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Authors: Agnese Pavlova, Aigars Reinis, Liga Berzina-Cimdina, Juta Kroica, Aleksandra Burlakova, Kristaps Rubenis
Abstract: Extrusion is a perspective forming technology for obtaining objects with certain profile, important for the TiO2 application as biomaterial. Extruded samples were calcinated at 1100 °C, thermally treated in different atmospheres: at 1450 °C in air and at 1300 °C in vacuum. An approach was made to examine the adhesion and colonization intensity of Staphylococcus epidermidis and Pseudomonas aeruginosa on TiO2 ceramic in vitro. It was found that Ps.aeruginosa demonstrated higher adhesion and colonization intensity as S.epidermidis and TiO2 samples treated in vacuum demonstrated higher attachment of microorganisms as TiO2 samples treated in air. It was supposed that surface charge promoted the bacterial adhesion on the vacuum treated samples.
Authors: Lasma Poca, Arita Dubnika, Dagnija Loca, Liga Berzina-Cimdina
Abstract: In the present study, the in vitro bioactivity of silver-doped hydroxyapatite (HAp/Ag) scaffolds was investigated. HAp/Ag was prepared using two different modified wet precipitation methods. The X-ray powder diffraction (XRD) results showed, that sintered HAp/Ag samples prepared using method (I) contain two phases HAp and Ag, but samples prepared by method (II) contain three different phases - HAp, Ag and AgO. After 2 month incubation period in simulated body fluid (SBF), surface of HAp/Ag scaffolds was coated with bone-like apatite. Thickness of bone-like apatite layer increased from 2 μm up to 32 μm, increasing the incubation period.
Authors: Liga Berzina-Cimdina, R. Cimdins, D. Vempere, I. Knets
Authors: Zilgma Irbe, Dagnija Loca, Ivita Bistrova, Liga Berzina-Cimdina
Abstract: Conventional calcium phosphate bone cements are self setting water based pastes. Recently pre-mixed calcium phosphate bone cements have been proposed that have non-aqueous fluid as liquid phase of the paste. Such cements thus only start setting reaction in contact with body fluids. In this work the properties (cohesion, compressive strength, phase composition) of pre-mixed calcium phosphate cements based on α-tricalcium phosphate and calcium dihydrogen phosphate monohydrate are described. Properties of several cement compositions are examined and compared to properties of β-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements. It was found that α-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements have higher compressive strength (10 - 15 MPa) than corresponding β-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements (10 - 6 MPa). Out of examined cement paste liquids (glycerol, polyethylene glycol and polypropylene glycol) cements using glycerol as the liquid phase had higher compressive strength and are more cohesive.
Authors: Kristine Salma, Zilgma Irbe, Dmitrijs Jakovlevs, Natalija Borodajenko, Liga Berzina-Cimdina
Abstract: In this work three different preparation techniques of biphasic calcium phosphate (BCP) bioceramics (consisting of both hydroxyapatite (HAp) and β-tricalcium phosphate (TCP)) are compared: sintering of synthetic calcium-deficient apatites (CDAs) (intimate mixture of HAp and TCP - SBCP), sintering of mechanical mixture of synthetic HAp and apatitic tricalcium phosphate (Ap-TCP) - MBCP and sintering of mechanical mixture of synthetic HAp and calcium metaphosphate glass (CMG) - GBCP. Two different HAp/TCP phase ratios were investigated: 20/80 and 60/40. Phase composition, microstructure, sintering properties and microporosity of obtained BCP bioceramics were investigated. The open porosity of prepared BCP bioceramics is strongly influenced by phase composition and preparation technique. BCP bioceramics SBCP and MBCP have homogeneous microstructure, whereas GBCP has inhomogeneous inclusions of dense TCP. High content of hydroxyapatite (HAp) phase in MBCP and SBCP correlates with high microporosity.
Authors: Arita Dubnika, Dagnija Loca, Liga Berzina-Cimdina
Abstract: One of the most used calcium phosphate implant materials in bone tissue regeneration is synthetic hydroxyapatite, which is similar to mineral phase of bone. By adding antibacterial effect to hydroxyapatite properties and creating controlled drug delivery systems based on this material, it is possible to obtain multifunctional material. Thus, in this study hydroxyapatite was doped with silver up to 1 wt% to provide antibacterial effect and from the obtained material dense and porous scaffolds were prepared. Prepared scaffolds were coated with chitosan and cross-linked with dexamethasone sodium phosphate (DEXA). Scaffolds were characterized and it is shown that linkage between chitosan coating and DEXA on the surface of hydroxyapatite and silver doped hydroxyapatite can ensure the controlled drug release up to 70 h.
Authors: Kristine Salma-Ancane, Liga Stipniece, Zilgma Irbe, Marina Sokolova, Guna Krieke, Liga Berzina-Cimdina
Abstract: 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.
Authors: Agnese Pura, Janis Locs, Liga Berzina-Cimdina
Abstract: TiO2 samples were obtained by extrusion process, sintered in air at 1000 °C, 1100 °C, 1200°C and 1300 °C and, afterwards, thermally treated under vacuum conditions at 1250 °C for 1 hour applying two different heating/cooling rates (2 °C/min and 5 °C/min). It was found that thermal treatment conditions substantially affected thermoelectric properties of the samples. Increasing sintering temperature, during the sample thermal treatment in air, the electrical conductivity of the specimens increased, while Seebeck coefficient decreased. With an increase in the heating rate during the vacuum heat treatment of the samples, the electrical conductivity of the samples decreased, while Seebeck coefficient increased.
Authors: Janis Locs, Liga Berzina-Cimdina, Aivars Zhurinsh, Dagnija Loca
Abstract: Pine tree (Pinus silvestris) with shaped sample dimensions of 20 x 20 x 5mm (axial) was selected as raw material. Samples were dried and, for half of samples, resin extraction from sample was applied. SiO2 sol was prepared using sol-gel technology. Ethanol, tetraetoxysilane, distilled water and hydrochloric acid was used as sol raw materials. Samples were impregnated under different vacuum and pressure conditions. Impregnation efficiency and gel take up volume, as well as SiO2 distribution in the samples, were studied. Impregnated samples were pyrolysed at 500 oC under oxygen-free atmosphere. Fourier transformation infrared spectroscopy (FT-IR) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) was used for sample investigations.
Authors: Inga Narkevica, Jurijs Ozolins, Liga Berzina-Cimdina
Abstract: Surface properties of a material play a significant role in manipulating biological response of living body to artificial materials. The aim of this work was put on bioactivity assessment of TiO2 ceramic after thermal treatment and further surface activation with UV-light. The in vitro apatite-forming ability was examined by soaking the samples into the simulated body fluid for several days. The research shows that nanostructural surface and UV irradiation accelerates formation of apatite on TiO2 pellets.
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