Browsing by Author "Staneva A.D."

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    Antibiofouling activity of graphene materials and graphene-based antimicrobial coatings
    (2021-09-01) Staneva A.D.; Dimitrov D.K.; Gospodinova D.N.; Vladkova T.G.
    Microbial adhesion and biofilm formation is a common, nondesirable phenomenon at any living or nonliving material surface in contact with microbial species. Despite the enormous efforts made so far, the protection of material surfaces against microbial adhesion and biofilm formation remains a significant challenge. Deposition of antimicrobial coatings is one approach to mitigate the problem. Examples of such are those based on heparin, cationic polymers, antimicrobial peptides, drug-delivering systems, and other coatings, each one with its advantages and shortcomings. The increasing microbial resistance to the conventional antimicrobial treatments leads to an increasing necessity for new antimicrobial agents, among which is a variety of carbon nanomaterials. The current review paper presents the last 5 years’ progress in the development of graphene antimicrobial materials and graphene-based antimicrobial coatings that are among the most studied. Brief information about the significance of the biofouling, as well as the general mode of development and composition of microbial biofilms, are included. Preparation, antibacterial activity, and bactericidal mechanisms of new graphene materials, deposition techniques, characterization, and parameters influencing the biological activity of graphene-based coatings are focused upon. It is expected that this review will raise some ideas for perfecting the composition, structure, antimicrobial activity, and deposition techniques of graphene materials and coatings in order to provide better antimicrobial protection of medical devices.
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    Fucoidan-Containing, Low-Adhesive Siloxane Coatings for Medical Applications: Inhibition of Bacterial Growth and Biofilm Development
    (2023-05-01) Vladkova T.G.; Staneva A.D.; Avramova I.A.; Ivanova I.A.; Gospodinova D.N.
    The deposition of low-adhesive siloxane coatings is a current trend for the non-toxic control of bacterial growth and biofilm formation. Total elimination of biofilm formation has not been reported so far. The aim of this investigation was to study the ability of a non-toxic, natural, biologically active substance, such as fucoidan, to inhibit bacterial growth on similar medical coatings. The fucoidan amount was varied, and its impact on the bioadhesion-influencing surface characteristics, as well as on bacterial cell growth, was investigated. The inclusion of up to 3–4 wt.% brown algae-derived fucoidan in the coatings increases their inhibitory effect, more significantly on the Gram-positive bacterium S. aureus than on the Gram-negative bacterium Escherichia coli. The biological activity of the studied siloxane coatings was ascribed to the formation of a low-adhesive, biologically active surface top layer consisting of siloxane oil and dispersed water-soluble fucoidan particles. This is the first report on the antibacterial activity of fucoidan-containing medical siloxane coatings. The experimental results give reason to expect that relevantly selected, natural biologically active substances can be efficient in the non-toxic control of bacterial growth on medical devices and, as a result, medical device-associated infections.
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    PREPARATION AND ANTIMICROBIAL ACTIVITY OF FUCOIDAN CONTAINING COLLAGEN/(ZnTiO3/SiO2) COMPOSITES
    (2023-01-01) Vladkova T.G.; Martinov B.L.; Staneva A.D.; Ivanova I.A.; Gospodinova D.N.; Albu-Kaya M.G.
    The aim of this investigation was to develop collagen based composite biomaterial with improved antimicrobial activity using a combination of antimicrobial agents consisting of zinc titanate embedded in a silane matrix, (ZnTiO3/ SiO2) and fucoidan at varied concentrations. The morphology of the investigated porous collagen/(ZnTiO3/SiO2)/ fucoidan composites was observed by SEM and their antimicrobial activity was evaluated against four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Pseudomonas putida, Salmonela holeresius), two Grampositive bacteria (Staphylococcus epidermidis, Bacillus cereus) and two fungi (Candida Lusitania, Saccharomyces cerevisiae) by disk diffusion test. Broad-spectrum antimicrobial activity of the studied porous collagen/(ZnTiO3/SiO2)/fucoidan composites was demonstrated, specific toward the different test microbial strains and dependent on the fucoidan concentration. The specific activity toward different microbial cultures was ascribed to the features of the microbial cells (size, shape, cell wall and membrane) and differences in the composition of the secreted exopolymeric substances. It was found that both, the formed interconnected open porous structure of the mixed collagen/fucoidan matrix with fine dispersed submicron ZnTiO3/SiO2 particles along the marix fibrils and the own antibacterial activity of the fucoidan, contribute to the increased wide spectrum antibacterial activity compared to that of similar collagen composites do not containing fucoidan.
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    Synthesis and characterization of nanosized ZnTiO3doped with reduced graphene oxide (RGO)
    (2021-02-16) Martinov B.L.; Staneva A.D.; Vlakhov T.E.; Slavov S.; Dimitrov D.; Marinov Y.G.; Hadjichristov G.B.
    Composite materials based on nanosized zinc titanate (ZnTiO3) doped with reduced graphene oxide (RGO) were obtained by means of ultrasonically assisted precipitation. In these composites, the concentration of RGO nanopartiles was varied from 1 wt.% to 20 wt.%. The ZnTiO3 ceramic was produced by sol-gel method. RGO was prepared by a modified Hammers method and subsequent chemical reduction with sodium borohydride. Structural and phase characterization of the fabricated composites was performed by XRD, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). It was identified that for all of the studied samples of the RGO/ZnTiO3 series, the two phases are uniformly distributed over the observed areas, which proves the formation of homogeneous nanocomposite materials. The electrical properties of the series of RGO/ZnTiO3 samples were characterized by complex electrochemical impedance spectroscopy (EIS) in the frequency range from 0.1 Hz to 1 MHz. The results obtained by EIS for the electrical conductance of RGO-doped ZnTiO3 as a function of the concentration of RGO nanoparticles were correlated with the data from structural studies.