Browsing by Author "Bryaskova R."
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Item Experimental Study on the Components in Polyvalent ``ghost`` Salmonella Vaccine for Veterinary Use(2015-01-01) Pencheva D.; Velichkova E.; Sandarov D.; Cardoso A.; Mileva M.; Genova-Kalou P.; Bryaskova R.Development of ``ghost`` Salmonella vaccines, inactivated by using a hybrid nanomaterial based on silver nanoparticles (AgNps) stabilized via polyvinyl alcohol (PVA), is an innovative approach in vaccine production. For this purpose, a series of attempts to establish the components of the polyvalent ``ghost`` Salmonella vaccine and the most suitable methods for its preparation were performed. The following strains S. Enteritidis, S. Newport-Puerto Rico, and S. Typhimurium were chosen as appropriate candidates for their incorporation in order to create polyvalent Salmonella ``ghost`` vaccine for veterinary use.Item Immobilization of trichosporon cutaneum R57 on PVA/TEOS/ MPTEOS hybrid matrices for removal of manganese ions(2013-10-17) Georgieva N.; Bryaskova R.; Lazarova N.; Racheva R.New hybrid materials based on polyvinyl alcohol (PVA), 3-mercaptopropyltriethoxysilane (MPTEOS) and tetraethoxysilane (TEOS) were prepared, using a sol-gel process. Thermogravimetric analysis (TGA) was performed to determine the thermal stability of the hybrid materials. MPTEOS, as a precursor, ensured the presence of SH-groups, thus providing additional binding places for cell immobilization. Based on good adhesive behavior, the hybrid materials were tested as matrices for immobilization of Trichosporon cutaneum R57 for removal of manganese ions from aqueous solutions. Maximum Mn2+ removal was achieved by cells immobilized onto materials with higher MPTEOS concentration. The synthesized PVA/TEOS/MPTEOS hybrid materials proved to be efficient for use in biosorption applications. © Biotechnol. & Biotechnol. Eq.Item Novel antibacterial hybrid materials based on polyvinyl alcohol and mercaptopropyltriethoxysilane with embedded silver nanoparticles (PVA/AgNps/MPTES)(2015-05-01) Zhao G.; Chen J.; Huang Y.; Bryaskova R.Abstract Hybrid materials based on polyvinyl alcohol (PVA) and mercaptopropyltriethoxysilane (MPTES) with embedded silver nanoparticles (AgNps) have been synthesized via a sol?gel method. Silver nanoparticles were obtained via thermal reduction in the presence of PVA as a stabilizer and reducing agent. The formation of silver nanoparticles within the PVA/MPTES matrix was proven by FTIR, XRD, and TEM analysis. The antibacterial activity of PVA/AgNps/MPTES materials was determined against strains belonging to Gram-positive and Gram-negative bacteria by disk diffusion and growth curve methods. The hybrid materials showed high antibacterial activity, which depends on the concentration of the silver nanoparticles.Item Novel Fluorescent Benzimidazole-Hydrazone-Loaded Micellar Carriers for Controlled Release: Impact on Cell Toxicity, Nuclear and Microtubule Alterations in Breast Cancer Cells(2023-06-01) Bryaskova R.; Georgiev N.; Philipova N.; Bakov V.; Anichina K.; Argirova M.; Apostolova S.; Georgieva I.; Tzoneva R.Fluorescent micellar carriers with controlled release of a novel anticancer drug were developed to enable intracellular imaging and cancer treatment simultaneously. The nanosized fluorescent micellar systems were embedded with a novel anticancer drug via the self-assembling behavior of well-defined block copolymers based on amphiphilic poly(acrylic acid)-block-poly(n-butyl acrylate) (PAA-b-PnBA) copolymer obtained by Atom Transfer Radical Polymerization (ATRP) and hydrophobic anticancer benzimidazole-hydrazone drug (BzH). Through this method, well-defined nanosized fluorescent micelles were obtained consisting of a hydrophilic PAA shell and a hydrophobic PnBA core embedded with the BzH drug due to the hydrophobic interactions, thus reaching very high encapsulation efficiency. The size, morphology, and fluorescent properties of blank and drug-loaded micelles were investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM), and fluorescent spectroscopy, respectively. Additionally, after 72 h of incubation, drug-loaded micelles released 3.25 μM of BzH, which was spectrophotometrically determined. The BzH drug-loaded micelles were found to exhibit enhanced antiproliferative and cytotoxic effects on MDA-MB-231 cells, with long-lasting effects on microtubule organization, with apoptotic alterations and preferential localization in the perinuclear space of cancer cells. In contrast, the antitumor effect of BzH alone or incorporated in micelles on non-cancerous cells MCF-10A was relatively weak.Item Novel magnetic composites based on water soluble unsaturated polyester resin and iron oxide nanoparticles(2016-06-01) Velev P.; Bryaskova R.Magnetic nanocomposites on the basis of water soluble unsaturated polyester resin filled with different amount of iron oxide nanoparticles have been successfully prepared. The mechanical properties of thus prepared composites as tensile, impact and flexural strength were determined. The specific volume and surface resistance of the magnetic nanocomposites were also determined.Item PORPHYRINE/SILVER NANOPARTICLES BASED PHOTOACTIVE ANTIBACTERIAL COATINGS(2023-01-01) Philipova N.; Georgiev N.; Ganchev D.; Lalov I.; Bryaskova R.A novel amino-modified protoporphyrin IX with included silver nanoparticles (PPIX-ED/AgNPs) complex was synthesized and used as a last layer for preparation of photoactive antibacterial coatings. The obtained PPIX-ED/ AgNPs complex was appropriately analyzed using various spectroscopic methods such as fluorescence analysis and infrared spectroscopy (ATR-FTIR). The size and morphology of the synthesized PPIX-ED/AgNPs complex were analyzed by Transmission electron microscopy (TEM) and dynamic light scattering (DLS). Then, the photoactive antibacterial coatings were obtained by deep coating procedure as the last layer consists of PPIX-ED/AgNPs complex, which is expected to possess strong antibacterial activity. The EDX-SEM analysis was employed to prove the deposition of the layers and nanoindentation analysis was used to determine their mechanical properties. The antibacterial properties of the photoactive coatings against G. negative E. coli and G. positive B. Subtilis were determined using disk diffusion method (DDM).Item PREPARATION OF GOLD LOADED MICELLES BASED ON POLY (ETHYLENE GLYCOL) - b - POLY (4-VINYL PYRIDINE) COPOLYMERS AS A TOOL FOR BIOMEDICAL APPLICATIONS(2017-01-01) Vircheva S.; Bryaskova R.; Miloshev S.; Tzoneva R.; Dishovsky N.Well-defined block copolymers based on poly (ethylene glycol) monomethyl ether and poly (4-vinyl pyridine) (PEG-b-P4VP) were prepared by atom transfer radical polymerization (ATRP). PEG-b-P4VP block copolymer self assembled in an aqueous medium with formation of nanosized spherical micelles was thus prepared. Gold nanoparticles were successfully loaded into PEG-b-P4VP based micelles. This was confirmed by UV-vis, TEM and DLS analysis. The cytotoxicity of gold loaded micelles against MDA-MB-231 breast cancer cells and L929 fibroblasts was determined.Item Removal of cadmium and copper ions by Trichosporon cutaneum R57 cells immobilized onto polyvinyl alcohol/tetraethoxysilane hybrid matrices(2010-06-16) Bryaskova R.; Georgieva N.; Peshev D.Polyvinyl alcohol (PVA) and tetraethoxysilane (TEOS) hybrid materials were prepared by sol-gel methods and tested as matrices for immobilization of Trichosporon cutaneum R57, capable of removing cadmium and copper ions from aqueous solutions. A kinetic model was applied and the effects of matrix TEOS content on the copper and cadmium uptake equilibria and rate constants were investigated. © 2010 Versita Warsaw and Springer-Verlag Wien.Item Sarcosine oxidase encapsulated polyvinyl alcohol-silica-AuNP hybrid films for sarcosine sensing electrochemical bioelectrode(2014-01-01) Lad U.; Kale G.; Bryaskova R.The amperometric response of sarcosine was measured in aqueous media containing ferrocene monocarboxylic acid using the redox enzyme sarcosine oxidase (SOD) immobilized in a composite material based on polyvinyl alcohol (PVA) and partially prehydrolyzed tetraethyl orthosilicate (pphTEOS) at the surface of ``in-house`` fabricated graphite electrodes. For comparison, separate electrodes consisting of silver and gold nanoparticles (Ag/AuNPs) embedded in the PVA-pphTEOS matrix was prepared employing a novel sol-gel process based on the in situ chemical reduction of Ag or Au ions using PVA both, as a reducing agent and stabilizer. The analytical performance of the enzyme electrodes was studied in terms of linear ranges, sensitivities, response times, limits of detection, reproducibility and stability. © 2014 The Electrochemical Society. All rights reserved.Item Study of multiblock polyamide-6/Poly-(isoprene) copolymers by positron annihilation spectroscopy(2008-11-10) Bryaskova R.; Mateva R.; Djourelov N.; Krasteva M.Positron annihilation lifetime spectroscopy (PALS) has been used to determine the free volume in multiblock polyamide-6/poly-(isoprene) copolymers (PA-6/PI), synthesized via activated anionic bulk copolymerization. The diisocyanate functionalized telechelic PI, blocked with caprolactam (CL) has been used as a commoner and an activator at the same time. The elastic PI block incorporated into the main chain of PA-6 affects the amorphous and crystal phase of the copolymer leading to changing in degree of crystallinity. The positron annihilation lifetime spectroscopy (PAL) and Doppler broadening of annihilation line (DBAL) technique in a set of pure PA-6 and PA-6/PI copolymers with two different compositions have been applied and evaluation of the size of free-volume holes (pores), localized mainly in the disordered regions of the PA-6/PI copolymer by measuring the o-Ps lifetime (τ3) and o-Ps intensity (I3) has been performed. © Versita Warsaw and Springer-Verlag Berlin Heidelberg 2008.Item SURFACE AND MECHANICAL PROPERTIES OF BIO-INSPIRED COATINGS(2021-01-01) Philipova N.; Mineva N.; Bryaskova R.In this article we report on the surface and mechanical properties of bio-inspired polymer coatings, obtained by the deposition of two consequent polymer layers on stainless steel (SS) substrate. As a first layer was employed 3,4-dihydroxy-phenylalanine (DOPA) functionalized P(mDOPA)-co-P(DMAEMA+) polycation which anchor to the surface by DOPA/metal interaction. The second layer consists in nanogels on the basis of Pox(mDOPA)/PAH. The deposition of the layers was confirmed by Quartz crystal microbalance coupled with dissipation (QCM-D) and proved by ATR-FTIR spectroscopy. The surface properties were demonstrated by AFM and contact angle measurements. The adhesion of the coating to the substrate was evaluated using scratch test and SEM analysis was applied to visualize the scratch tracks.Item Synthesis and characterization of diblock copolymers based on poly (ethylene glycol) and poly (4-vinyl pyridine) via atom transfer radical polymerization(2015-01-01) Vircheva S.; Bryaskova R.; Miloshev S.; Dishovsky N.Atom transfer radical polymerization (ATRP) was applied for the preparation of block copolymers based on poly (ethylene glycol) monomethyl ether and poly (4-vinyl pyridine) (MeOPEG-b-P4VP). This was achieved using chloro-terminated PEG as a macroinitiator. Further, the ATRP was performed using 4-VP as a second forming block in the presence of CuCl/PMDETA as a catalyst system. The successful formation of MeOPEG-b-P4VP block copolymers was proved by 1H NMR with the presence of all characteristic signals arising from PEG and 4-VP units. The GPC results showed the preparation of well-defined block copolymers with low dispersity, which confirms the controlled character of radical polymerization. The thermal properties of thus prepared copolymers were characterized by TGA analysis.Item Synthesis and comparative study on the antimicrobial activity of hybrid materials based on silver nanoparticles (AgNps) stabilized by polyvinylpyrrolidone (PVP)(2011-10-01) Bryaskova R.; Pencheva D.; Nikolov S.; Kantardjiev T.Hybrid materials based on polyvinylpyrrolidone (PVP) with silver nanoparticles (AgNps) were synthesized applying two different strategies based on thermal or chemical reduction of silver ions to silver nanoparticles using PVP as a stabilizer. The formation of spherical silver nanoparticles with diameter ranging from 9 to 16 nm was confirmed by TEM analysis. UV-vis and FTIR spectroscopy were also applied to confirm the successful formation of AgNps. The antibacterial activity of the synthesized AgNPs/PVP against etalon strains of three different groups of bacteria - Staphylococcus aureus (S. aureus; grampositive bacteria), Escherichia coli (E. coli; gram-negative bacteria), Pseudomonas aeruginosa (P. aeruginosa; nonferment gram-negative bacteria), as well as against spores of Bacillus subtilis (B. subtilis) was studied. AgNps/PVP were tested for the presence of fungicidal activity against different yeasts and mold such as Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Aspergillus brasiliensis. The hybrid materials showed a strong antimicrobial effect against the tested bacterial and fungal strains and therefore have potential applications in biotechnology and biomedical science. © Springer-Verlag 2011.Item THERMAL PROPERTIES OF PVA/TEOS/AgNps THIN HYBRID FILMS AND THEIR FUNGICIDAL ACTIVITY TOWARDS REPRESENTATIVES OF GENUS CANDIDA(2022-01-01) Bryaskova R.; Pencheva D.The role of Candida infections in patients with weakened immune systems or hospitalized and catheterized patients is a worldwide problem with increasing importance. Due to the high fungal resistance to different type antifungals drugs, nowadays, the attention is paid towards novel hybrid coatings possessing strong antibacterial and fungicidal properties. The present article deals with the thermal behavior and fungicidal properties of novel hybrid materials based on polyvinyl alcohol (PVA)/tetraethyl orthosilicate (TEOS) films with included silver nanoparticles (AgNps) synthesized by sol-gel method. Thermal properties of the hybrid materials were investigated using TGA and DSC analysis. The fungicidal activity of the synthesized hybrid materials with included silver nanoparticles were tested onto control and clinical strains of genus Candida resistant to different antifungals. The antifungal activity of the synthesized materials was determined by Disk Diffusion Method (DDM) were the zone of inhibition of hybrid materials against control and clinical strains was monitoring.