Papers by Author: Dagnija Loca

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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: Dagnija Loca, Janis Locs, Juris Gulbis, Ilze Salma, Liga Berzina-Cimdina
Abstract: Local drug delivery devices especially based on osteoconductive porous calcium phosphate ceramics are of clinical importance. However, the brittleness, pore structure, porosity and pore size should be controlled for their wider applications in hard tissue implants and load bearing compartments. An approach to the fabrication of the bone graft exhibiting bone regeneration function as well as the local drug delivery was made. Hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) porous scaffolds were prepared and mechanical properties (compression strength 20MPa), porosity (>50%), pore size (60-350µm) and structure as well as interconnectivity of pores were investigated. Porous scaffolds were impregnated with 4-5 mg of lidocaine hydrochloride (LidHCl) and drug release rate was evaluated and compared for scaffolds with and without poly lactic acid (PLA), poly(-caprolactone) (PCL) and polyvinyl alcohol (PVA) coatings. From in vitro dissolution tests it was seen that biopolymer coatings sustained the drug release up to 12h.
Authors: Agnese Pavlova, Liga Berzina-Cimdina, Janis Locs, Dagnija Loca, Joerg Bossert
Abstract: In past years scientists have interest in new specific TiO2 properties, which result from oxygen and titanium ratio in ceramic. Recently such TiO2 applications as implantable biomaterials in medicine and photocatalysts in purification of waste water become very significant. High temperature vacuum treated titanium oxide ceramics become biologically active and decrease microbiological water pollution when used as electrodes in electrochemical water treatment. In most of these cases highly dense ceramics are requested. TiO2 low-temperature modification anatase and TiO2 high-temperature modification rutile was used during the investigation. Different additives were used to improve particle packing and increase green density of pressed pellets as well as following sinter density. During the investigation it was found that green density of the samples depends not only on powder characteristics such as particle size distribution, grain size, mineralogical composition of raw material, quantity and nature of additives used in mass preparation procedure but also on kind and magnitude of compaction and sintering conditions.
Authors: Dagnija Loca, Osvalds Pugovics, Liga Berzina-Cimdina, Janis Locs
Abstract: Microencapsulation of highly water soluble pharmaceutical substances (solubility more than 1g/ml), especially if high drug loading is required (more than 50%) is a big challenge. Biodegradable polylactide as coating material and polyvinyl alcohol as surfactant were found suitable for this purpose. Active substance was microencapsulated using slightly modified waterin- oil-in-water technique which involves dissolving of the drug in the water and polymer in methylene chloride and forming an emulsion in water using a surfactant. Procedure of microencapsulation was followed by filtration and drying of product obtained. Not only the developed method enables microencapsulation of highly water soluble pharmaceuticals, but it also predicts properties of products obtained. Microencapsulation technique developed allows encapsulation of highly water soluble pharmaceutical with drug load up to 80%, and encapsulation efficiency up to 65%. During the study such parameters as emulsification time, volume of outer water phase and amount of active ingredient in inner water phase on microencapsulation process and product properties were investigated
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