Browsing by Author "Vladkova T."
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Item Collagen/(ZnTiO3/SiO2) composites of an wide spectrum antimicrobial activity(2020-01-01) Vladkova T.; Staneva A.; Albu-Kaya M.; Martinov B.; Ivanova I.The aim of this study is to prepare collagen composites of an increased wide spectrum antimicrobial activity using zinc titanate embedded in a silane matrix (ZnTiO3 /SiO2). Aiming to improve the predictability between the patient outcome and the in vitro antimicrobial testing, four Gram-negative, two Gram-positive bacterial strains, two fungi and seven mixed cultures are used in this study. A higher antimicrobial activity of Collagen/(ZnTiO3/SiO2) composites as compared to that of Collagen/ZnTiO3 ones is found against all test mono-microbial strains. Collagen/(ZnTiO3 /SiO2) composites demonstrate also an well expressed action against the mixed test bacterial cultures, in the most cases a better one compared to that against the bacteria participating in the corresponding mixed bacterial cultures. The increased antimicrobial effect is due to a more homogeneous distribution of the submicron ZnTiO3 aggregates embedded in a silane matrix along the collagen fibrils and a formation of a specific, snail-like structure depicted by SEM. The specific activity against different microbial cells and mixed bacterial cultures is ascribed to features of the microbial cells: size, shape, cell membrane and walls as well as to different exopolymeric substances (EPSs) and their concurrent adsorption in cases of mixed bacterial cultures, as well as the EPSs concurrent adsorption being similar to the concurrent protein adsorption from blood plasma known as Vroman's effect. The wide spectrum high activity against fungi, mono-and multi-specie bacterial cultures makes the studied Collagen/(ZnTiO3 /SiO2) composites a promising antimicrobial biomaterial.Item Composition antifouling coating: Effect of siloxane and fluorinated oil incorporation on marine biofilm formation(2014-01-01) Akuzov D.; Vladkova T.; Klöppel A.; Brümmer F.; Murthy S.Composition polysiloxane based coatings are currently the only viable commercial alternative of the toxic biocide containing antifouling paints. Oil incorporation improves the foul-releasing ability of the polysiloxane coatings. The impact of non-reactive, different molecular mass, both siloxane and fluorinated oil on the biofilm formation onto developed by us polysiloxane composition coating is presented. It is evaluated in laboratory and field experiments on the ground of the determination of the elastic modulus, water contact angle, critical surface tension, surface roughness and topography.Item Current approaches to reduction of marine biofilm formation(2014-01-01) Vladkova T.; Akuzov D.; Klöppel A.; Brümmer F.Biofilm formation is the initial step ofthe complex marine biofouling process, limiting the performance ofsubmerged surfaces in numerous applications. No technology is known up to now capable to stop the marine biofilm development even on biocidal paints coated surfaces. Several non-toxic approaches for control over marine biofilms based on physi-cal, chemical or/and biological methods, most of them inspired by the nature, are currently on search. Surface patterning, enzyme alternatives of toxic biocides and nature derived anti-biofilm agents (natural biocides, bio-surfactants/dispersants and quorum sensing inhibitors) are in the scope of this review.Item Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations(2019-05-01) Ramstedt M.; Ribeiro I.A.C.; Bujdakova H.; Mergulhão F.J.M.; Jordao L.; Thomsen P.; Alm M.; Burmølle M.; Vladkova T.; Can F.; Reches M.; Riool M.; Barros A.; Reis R.L.; Meaurio E.; Kikhney J.; Moter A.; Zaat S.A.J.; Sjollema J.In Europe, the mean incidence of urinary tract infections in intensive care units is 1.1 per 1000 patient-days. Of these cases, catheter-associated urinary tract infections (CAUTI) account for 98%. In total, CAUTI in hospitals is estimated to give additional health-care costs of £1–2.5 billion in the United Kingdom alone. This is in sharp contrast to the low cost of urinary catheters and emphasizes the need for innovative products that reduce the incidence rate of CAUTI. Ureteral stents and other urinary-tract devices suffer similar problems. Antimicrobial strategies are being developed, however, the evaluation of their efficacy is very challenging. This review aims to provide considerations and recommendations covering all relevant aspects of antimicrobial material testing, including surface characterization, biocompatibility, cytotoxicity, in vitro and in vivo tests, microbial strain selection, and hydrodynamic conditions, all in the perspective of complying to the complex pathology of device-associated urinary tract infection. The recommendations should be on the basis of standard assays to be developed which would enable comparisons of results obtained in different research labs both in industry and in academia, as well as provide industry and academia with tools to assess the antimicrobial properties for urinary tract devices in a reliable way.Item Fabrication and characterization of antimicrobial magnetron cosputtered TiO2/Ag/Cu composite coatings(2021-04-01) Gospodonova D.; Ivanova I.; Vladkova T.The aim of this study was to prepare TiO2/Ag/Cu magnetron co-sputtered coatings with controlled characteristics and to correlate them with the antimicrobial activity of the coated glass samples. The elemental composition and distribution, surface morphology, wettability, surface energy and its component were estimated as the surface characteristics influencing the bioadhesion. Well expressed, specific, Ag/Cu concentration-dependent antimicrobial activity in vitro was demonstrated toward Gram-negative and Gram-positive standard test bacterial strains both by diffusion 21 assay and by Most Probable Number of surviving cells. Direct contact and eluted silver/coper nanoparticles killing were experimentally demonstrated as a mode of the antimicrobial action of the studied TiO2/Ag/Cu thin composite coatings. It is expected that they would ensure a broad spectrum bactericidal activity during the indwelling of the coated medical devices and for at least 12 h after that, with the supposition that the benefits will be over a longer time.Item Low adhesive surfases for biofouling control(2018-01-01) Vladkova T.The current non-toxic biofouling control is based on the idea for creation of non-sticking, low adhesive material surfaces - an approach firstly applied to the creation of bionert, protein repellent biomaterials, where the strong hydrophilic, ``water like`` surfaces appeared to be very promising. Strong/super hydrophobic, low energy surfaces are preferable in the industrial and marine biofouling control because of their better stability in water media. A brief overview is presented for the theoretical base of low adhesive, non-fouling surfaces creation, some successful solutions and future prospects for development of anti-biofouling materials. It includes also the mode of development and biofilm composition, protein adsorption as a mediator of bioadhesion and biofouling; the most important prerequisites of the ``clean`` surface; integrated multiple technology for creation, including surface energetics alteration by topography (micro and nanostructuring) and chemistry manipulation, combined or not with quasy-irremovable surface layer deposition.Item Preparation and antimicrobial activity of collagen/(RGO/ZnO/TiO2/SiO2) composites(2020-01-01) Staneva A.; Albu-Kaya M.; Martinov B.; Ivanova I.; Vladkova T.A serial investigation is initiated aiming to explore the biological activity of some newly synthetized chemical compounds for the development of novel antimicrobial collagen based biomaterials. Collagen/ZnTiO3, Collagen/RGO, Collagen/(Ag/RGO), Collagen/(Ag/RGO/SiO2) and Collagen/(ZnTiO3/SiO2) composites have been so far studied and all of them demonstrate a specific antimicrobial activity against Gram-negative and Gram-positive bacteria and in some cases against fungi. The aim of this investigation is to develop new antimicrobial collagen biomaterials using RGO, ZnO, and TiO2 embedded in TEOS as another antimicrobial agent, combining the biological activity of RGO, ZnO and TiO2 with the dispersing effect of SiO2. The new Collagen/(RGO/ZnO/TiO2/SiO2) composites demonstrate an antimicrobial activity dependent on the agent loading level. It is specific in respect to Gram-negative, Grampositive bacteria and fungi. An optimal balance between the antimicrobial activity and the cytotoxicity is achieved by varying the concentration of the antimicrobial agent, RGO/ZnO/TiO2/SiO2, in Collagen/(RGO/ZnO/TiO2/SiO2) composites. It is suggested that the mechanism of the antimicrobial action includes the simultaneous proceeding of (i) metal ions chelation; (ii) free oxygen radicals formation due to the interactions between the microbial cells and the antimicrobial agent; (iii) mechanical demolition of the cell walls and membranes by RGO crystal nanoparticles. The broad spectrum antibacterial and anti-fungal activity combined with the low cytotoxicity at an optimal Collagen/ Antimicrobial agent ratio makes the studied Collagen/(RGO/ZnO/TiO2/SiO2) composites a promising antimicrobial material increasing the medical biomaterials assortment. © 2020 by the authors.Item Progresses in treatment of collagen and keratin-based materials with silver nanoparticles(2013-12-01) Gaidau C.; Petica A.; Micutz M.; Danciu M.; Vladkova T.The influence of different chemical systems on the interaction of collagen at the molecular level with silver nanoparticles in collagen- based materials is a very important source of information for designing leather technologies and treatments as ecological alternatives to organic preservatives currently used. The UV circular dichroism as a scientific tool to assess mainly the secondary structure of proteins in solution proved that silver nanoparticles are able to interact with collagen in aqueous medium in the presence of some classical cross- linkers and other chemical additives similar to those occurred in collagen-based materials. The most important influence on secondary structure of collagen was observed in the case of interaction with chemically and electrochemically synthesized silver nanoparticles in the presence of basic chromium salts with or without poly(hydroxy urethane). The treatment of chromium tanned sheepskins with poly(hydroxyl urethane) and dispersion of chemically synthesized nanosilver showed the best resistance to fungi and bacterial exposure tests. These collagen-based materials containing different amounts of nanosilver were investigated by Atomic Absorption Spectroscopy, Atomic Force Microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy. The influence of sheepskins treated with silver nanoparticles on the wound healing process was assessed and the nanoparticles concentration seems to have a positive effect up to 370 ppm and does not influence the inflammatory process above this concentration. © Versita Sp. z o.o.Item Recent Progress in Antioxidant Active Substances from Marine Biota(2022-03-01) Vladkova T.; Georgieva N.; Staneva A.; Gospodinova D.Background: The well-recognized but not fully explored antioxidant activity of marinebiota-derived, biologically active substances has led to interest in their study as substitutes of antibiotics, antiaging agents, anticancer and antiviral drugs, and others. The aim of this review is to present the current state of the art of marine-biota-derived antioxidants to give some ideas for potential industrial applications. Methods: This review is an update for the last 5 years on the marine sources of natural antioxidants, different classes antioxidant compounds, and current derivation biotechnologies. Results: New marine sources of antioxidants, including byproducts and wastes, are presented, along with new antioxidant substances and derivation approaches. Conclusions: The interest in high-value antioxidants from marine biota continues. Natural substances combining antioxidant and antimicrobial action are of particular interest because of the increasing microbial resistance to antibiotic treatments. New antioxidant substances are discovered, along with those extracted from marine biota collected in other locations. Byproducts and wastes provide a valuable source of antioxidant substances. The application of optimized non-conventional derivation approaches is expected to allow the intensification of the production and improvement in the quality of the derived substances. The ability to obtain safe, high-value products is of key importance for potential industrialization.Item Research on cold plasma treatment of leather and fur based materials as ecological alternative(2017-01-01) Gaidau C.; Niculescu M.; Surdu L.; Barbu I.; Vladkova T.; Dineff P.The paper presents the performances of leathers and fur skins pre-treated with cold plasma through dielectric barrier discharge (DBD) at atmospheric pressure and room temperature followed by treatment with chemical materials. The main improved properties were water repellency and flame resistance, two important characteristics for added value garments (water proof and fireman footwear), high quality furniture and automotive leather upholstery. The water drop resistance in static conditions reveals a hydrophobic effect on dermis surface induced by cold plasma pre-treatment, similar with chemical impregnation. The water resistance in dynamic conditions showed the reactivation of hydrophilic groups inside collagen and keratin based materials, similarly with other materials pre-treated with cold plasma presented in literature. The water quantity which penetrated the fur skins dermis decreased by 22.7% for the pre- treated samples with cold plasma and treated with silicon based materials as compared to samples not pre-treated with plasma. Full grain leathers pre-treated with cold plasma showed impermeable behavior and improved flame resistance. The influence of cold plasma pre-treatment was favorable for water repellency of leathers and fur skins and for flame retardant properties of different kinds of leathers.Item Sharply reduced biofilm formation from Cobetia marina and in black sea water on modified siloxane coatings(2018-04-01) Akuzov D.; Franca L.; Grunwald I.; Vladkova T.Siloxane fouling release coatings are currently the only viable non-toxic commercial alternative to toxic biocide antifouling paints. However, they only partially inhibit biofouling since biofilms remain a major issue. With the aim to improve the bacterial resistance of siloxane coatings modified with non-ionic surfactant (NIS), antioxidant (AO) or both NIS/AO, the ability of PEG-silane co-cross-linker was investigated to reduce Cobetia marina adhesion and multispecies biofilm formation from natural seawater. Surface physical-chemical and physical-mechanical parameters relevant to bio-adhesion were estimated before the testing of the biofilm formation. Slightly reduced biofilm from C. marina and sharply reduced multispecies biofilm, formed in natural sea water, were found on the PEG-silane co-cross-linked coatings without modifying additives. However, both C. marina growth and biofilm formation from natural sea water were sharply reduced on the PEG-silane co-cross-linked coatings containing NIS or AO, even more, no C. marina adhesion was seen on the coating containing NIS and AO simultaneously. Possible explanations of the observed effects are presented in this article. It was concluded that the PEG-silane co-cross-linker, toghether with NIS and AO, can be used as an efficient tool to additionally reduce the bioadhesion of Gram-negative marine bacteria and multispecies biofilm formation on siloxane antifouling coatings.Item Surface modification of silicone rubber with poly(ethylene glycol) hydrogel coatings(2004-05-05) Vladkova T.Hydrogel coatings of monoacrylated poly(ethylene glycol) (PEG) methyl ethers of different molecular weights were attached to silicon rubber surfaces and crosslinked with hexanediol diacrylate or ethoxylated trimethylolpropane diacrylate by UV polymerization. The wetting, evaluated with the water contact angles, correlated with the surface oxyethylene chain density, which was evaluated with the ESCA >C-O-/-CH2- ratio obtained from the C(1s) peak. As measured by the ESCA N(1s) peak, bovine serum albumin formed very thin protein adsorbates on the PEG-coated surfaces. A strong correlation was found between low protein adsorption and a high >C-O-/-CH2-ratio of the PEG-coated substrate. The PEG-coated silicon rubber also demonstrated very low cell and platelet adhesion. © 2004 Wiley Periodicals, Inc.