Browsing by Author "Vladkova T.G."

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    ANTI-BIOFILM AGENTS FROM MARINE BIOTA
    (2023-01-01) Vladkova T.G.; Martinov B.L.; Gospodinova D.N.
    Microbial biofilm forms on any living or non-living material surface contacting with microbial species. It is a persistent world-weight spread problem with very high prize. This explains the exclusive interest to development of anti-biofilm material surfaces. The continuously increasing microbial resistance to currently used antimicrobial agents requires looking for new ones. Marine biota is a rich source of biologically active substances with anti-biofilm potential that is scarily studied. The aim of this review is to outline the variety of marine sources delivering antimicrobial agents and their ability to inhibit different stages of the biofilm development, expecting to give some ideas for their utilization in the creation of improved antibiofilm material surfaces. It includes short information about the negative impact and cost, mode of development and composition of the microbial biofilms, as well as principle approaches to the inhibition with focus on the sources of biologically active substances and anti-biofilm agents from marine biota. The main conclusion is that the antibiofilm activity of many marine biota derived biologically active substances is not enough investigated although their strong bactericidal, antioxidant, surfactant and other activities are already proved and utilized in the medicine, cosmetic, food industry and others. This review is an update of the known to day on the marine sources derived anti-biofilm agents.
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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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    Comparative Study of the Marinobacter hydrocarbonoclasticus Biofilm Formation on Antioxidants Containing Siloxane Composite Coatings
    (2022-07-01) Vladkova T.G.; Monov D.M.; Akuzov D.T.; Ivanova I.A.; Gospodinova D.
    No systematic study of antioxidant containing coatings and their anti-biofilm action has been reported so far. The utilization of antioxidants in protective coatings to inhibit marine biofilm formation is a current challenge. The aim of this preliminary study was to prepare, characterize and compare the efficiency of low adhesive siloxane composite coatings equally loaded with different antioxidants against mono-species biofilms formation. Most often participating in the marine bio-films formation, Marinobacter hydrocarbonoclasticus was the test bacterium. Both the biofilm covered surface area (BCSA) and corrected total cell fluorescence (CTCF) (by fluorescent microscopy) were selected as the parameters for quantification of the biofilm after 1 h and 4 h incubation. Differing extents of altered surface characteristics (physical-chemical; physical-mechanical) and the specific affection of M. hydrocarbonoclasticus biofilm formation in both reduction and stimulation, were found in the studied antioxidant containing coatings, depending on the chemical nature of the used antioxidant. It was concluded that not all antioxidants reduce mono-species biofilm formation; an-tioxidant chemical reactivity stipulates the formation of an altered vulcanization network of the siloxane composites and thus microbial adhesion which influences the surface characteristics of the vulcanized coatings; and low surface energy combined with a low indentation elastic modulus are probably pre-requisites of low microbial adhesion.
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    Early stage anti-bioadhesion behavior of superhydrophobic soot based coatings towards Pseudomonas putida
    (2018-12-15) Esmeryan K.D.; Avramova I.A.; Castano C.E.; Ivanova I.A.; Mohammadi R.; Radeva E.I.; Stoyanova D.S.; Vladkova T.G.
    Biofilm development, associated with the adherence of microbial cells on various solid substrates, has an adverse economic impact and is the main reason for the spreading of microbial infections. The present article reports novel findings about the anti-bioadhesion performance of four types of superhydrophobic soot coatings, deposited via combustion flame synthesis and further functionalized using plasma polymerization and/or fluorination, towards a Gram-negative bacterial strain Pseudomonas putida. The real-time sensor response of four representative soot coated 5 MHz quartz crystal microbalances, along with scanning electron microscopy, fluorescence microscopy and contact angle measurements on the model soot surfaces, reveal reversible and irreversible bioadhesion on the soot during the first hour of cell colonization. Each adhesion mode is related to the presence and distribution of morphological features within the size of bacteria, but the prolonged 7-day exposure to the bacterial suspensions unifies the number of attached cells (only 3 times difference from coating-to-coating). Nevertheless, the soot coatings inhibit the proliferation of Pseudomonas species and reduce their quantity by two orders of magnitude compared to an uncoated glass slide, which demonstrates the importance of surface characteristics for precise control of the initial cell attachment and development of multifunctional soot coatings with anti-bioadhesion properties.
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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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    Plasma Based Approaches for Deposition and Grafting of Antimicrobial Agents to Polymer Surfaces
    (2022-01-01) Vladkova T.G.; Gospodinova D.N.
    Improved protection of urinary stents against infections is a significant current challenge because of the increasing microbial resistance to the conventional antibiotics and negative issues for the patients. Formation of crystalline biofilms of pathogenic microbial cells is the leading cause of urinary stent associated infections. A lot of approaches, antimicrobial agents and techniques are under a study to mitigate the problem by creation of contact killing; releasing or low adhesive surfaces do not allow attachment of microbial cells. The plasma treatment has a number of advantages that make it preferable in many strategies for the development of antimicrobial biomaterials. The control over the plasma processing parameters allows control over the surface chemistry, charge, structure, morphology, hydrophilic/hydrophobic balance, etc. Due to a variety of biomaterials and bacteria, causing urinary tract infections, plasma assisted antibacterial strategies need in tailoring to each specific surface. Plasma treatment of polymers under corresponding operation conditions allows deposition of contact killing, releasing (including controlled release) or low-adhesive antimicrobial coatings, as well as polymer surface functionalization and durable immobilization of antimicrobial molecules. Most of the plasma technologies are developed in laboratory and the surface engineered biomaterials are tested in vitro.
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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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    Recent Progress in Terrestrial Biota Derived Antibacterial Agents for Medical Applications
    (2024-10-01) Vladkova T.G.; Smani Y.; Martinov B.L.; Gospodinova D.N.
    Conventional antibiotic and multidrug treatments are becoming less and less effective and the discovery of new effective and safe antibacterial agents is becoming a global priority. Returning to a natural antibacterial product is a relatively new current trend. Terrestrial biota is a rich source of biologically active substances whose antibacterial potential has not been fully utilized. The aim of this review is to present the current state-of-the-art terrestrial biota-derived antibacterial agents inspired by natural treatments. It summarizes the most important sources and newly identified or modified antibacterial agents and treatments from the last five years. It focuses on the significance of plant- animal- and bacteria-derived biologically active agents as powerful alternatives to antibiotics, as well as the advantages of utilizing natural antibacterial molecules alone or in combination with antibiotics. The main conclusion is that terrestrial biota-derived antibacterial products and substances open a variety of new ways for modern improved therapeutic strategies. New terrestrial sources of known antibacterial agents and new antibacterial agents from terrestrial biota were discovered during the last 5 years, which are under investigation together with some long-ago known but now experiencing their renaissance for the development of new medical treatments. The use of natural antibacterial peptides as well as combinational therapy by commercial antibiotics and natural products is outlined as the most promising method for treating bacterial infections. In vivo testing and clinical trials are necessary to reach clinical application.
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    Recent Progress in Terrestrial Biota-Derived Anti-Biofilm Agents for Medical Applications
    (2024-09-01) Vladkova T.G.; Smani Y.; Martinov B.L.; Gospodinova D.N.
    The terrestrial biota is a rich source of biologically active substances whose anti-biofilm potential is not studied enough. The aim of this review is to outline a variety of terrestrial sources of antimicrobial agents with the ability to inhibit different stages of biofilm development, expecting to give some ideas for their utilization in improved anti-biofilm treatments. It provides an update for the last 5 years on anti-biofilm plant products and derivatives, essential oils, antimicrobial peptides, biosurfactants, etc., that are promising candidates for providing novel alternative approaches to combating multidrug-resistant biofilm-associated infections. Based on the reduction in bacterial adhesion to material and cell surfaces, the anti-adhesion strategy appears interesting for the prevention of bacterial attachment in combating a broad range of mono- and multispecies bacterial biofilms. So far, few studies have been carried out in this direction. Anti-biofilm coatings made by or containing biologically active products from terrestrial biota have scarcely been studied although they are of significant interest for a reduction in infections associated with medical devices. Combination therapy with commercial antibiotics and natural products is accepted now as a promising base for future advances in anti-biofilm treatment. In vivo testing and clinical trials are necessary for clinical application.
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    Surface engineered polymeric biomaterials with improved biocontact properties
    (2010-01-01) Vladkova T.G.
    We present many examples of surface engineered polymeric biomaterials with nanosize modified layers, controlled protein adsorption, and cellular interactions potentially applicable for tissue and/or blood contacting devices, scaffolds for cell culture and tissue engineering, biosensors, biological microchips as well as approaches to their preparation. Copyright © 2010 Todorka G. Vladkova.