Browsing by Author "Raykova R."

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    Antimycotic activity of sumac extract in composites based on epoxidized natural rubber for application in footwear soles production
    (2020-01-01) Dishovsky N.; Marinkova D.; Raykova R.; Vladimirova L.
    Biofilms are attached to different kinds of surfaces or associated with interfaces. The microbial communities are often composed of multiple species, which interact between each other. Attachment is complex process, regulated by diverse characteristics of the growing media, substrates and cell surface. Biofilms have different effects, which can affect changes in surface properties of polymer carriers. Accumulated biomass may provoke negative effects by direct attack, which leads to destruction of polymer matrixes. An option to solve the problem is introduction of bioactive ingredient into the composite. The aim of our study was to find and propose bioactive ingredients, derived from renewable sources, particularly such exhibiting of antimycotic influence, which can be included to elastomeric composite materials. These materials can be used for obtaining of winter footwear soles with adhesion, increasing to various types of icy surfaces. The influence of introduced antimycotic additive, extracted from Cotinus coggygria plant, was investigated. Antimycotic activity of obtained plant extracts against two eukaryotic strains was investigated by diffusion method in agar broth. The formation of biofilms from Candida lypolitica and Candida albicans strains onto natural rubber vulcanizates, kinetics and growth of biofilms strains were also observed.
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    Quartz crystal microbalance detection of aflatoxin B1 by self-assembled monolayer technique
    (2019-01-01) Raykova R.; Marinkova D.A.; Semerdzhieva V.A.; Michiel M.; Griesmar P.; Mourdjeva M.; Yaneva S.; Iliev I.T.
    Background: New biosensor techniques allowing detection of low concentrated substances show a great variety nowadays. The construction of a system with modified quartz as a part of a Quartz Crystal Microbalance (QCM) techniques helps the detection and confirmation of low toxin concentrations in a sample. Objective: The study aims to allow the application of methods for preparation and modification of the gold surface of piezoelectric crystal for detection of aflatoxin B1(AFB1) in the concentration range 0.2-2.0 µg/L by QCM technique (quartz-crystal microbalance). Methods: The procedure for the preparation of quartz crystal sensors for experimental purposes was performed. The quartz surface was activated and covered with self-assembled monolayer to immobilize antibody (rabbit anti-aflatoxin B1) for the detection of antigen-antibody reaction. Results: The G” corresponds to viscous properties of the material, during applied deformation of the material in the presence of different concentrations, which revealed in the sensitivity of the used resonator. Conclusion: Detection of toxic pollutants may be achieved via QCM methods, ultrasound resonator and piezoelectric quartz techniques for measurement. These techniques allow detection of significantly low concentrations of toxic pollutants, in particular, AFB1, compared to analysis with direct and indirect ELISA immunoassays.
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    Synthesis and investigation of the properties of hybrid materials for enzyme immobilization
    (2018-01-01) Yaneva S.; Semerdzhieva V.; Raykova R.; Marinkova D.; Chernev G.; Iliev I.; Yotova L.
    The chemical nature of carriers for enzyme immobilization plays an important role for retention of the enzyme activity and stability. Two new materials are synthesized for enzyme immobilization based on trimethoxy silane/cellulose acetate butyrate/poly (amido amine) dendrimers (TMOS/CAB/PAMAM) and methyltriethoxy silane/cellulose acetate propionate/ poly (amido amine) dendrimers (MTES/CAP/PAMAM). The synthesis is carried out via the sol-gel method, which allows the preparation of porous glasses through hydrolysis and poly-condensation at a low temperature using high purity initial materials. The PAMAM dendrimers are mono-dispersive, well defined and have a developed three dimensional structure of a high functional groups concentration. The obtained materials are used to investigate the properties of immobilized enzymes such as lipoxygenase and laccase. These enzymes are widely used in industry as bleaching agents. There is also data on application of laccase and lipoxygenase in preparation of biosensors for toxic pollutants determination. Biosensors with immobilized laccase are used to determine phenolic compounds, whereas immobilized lipoxygenase is applied to biosensors formulation for determining Aflatoxin B1 presence.