Browsing by Author "Foteva T."
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Item ANTIMICROBIAL PROPERTIES OF SILICA/HYDROXYPROPYLCELLULOSE HYBRIDS DOPED WITH COPPER IONS(2022-01-01) Foteva T.; Georgieva N.The subject of intense research is the creation of innovative materials with antimicrobial effect, which would find potential application in various fields such as food industry, pharmacy, medicine, agriculture, wastewater treatment. In the present study silica/hydroxypropylcellulose hybrids doped with copper ions from Cu(NO3)2 × 3H2O were obtained using sol-gel technique. The copper concentration in the hybrids varied from 0.5 wt. % to 5 wt. %. The antimicrobial potential of materials was investigated using reference strains for Gram-positive bacteria (Bacillus subtilis NBIMCC 3562), Gram-negative bacteria (Escherichia coli K12 NBIMCC 407) and yeast (Candida albicans NBIMCC 74). The experiments were based on the measurement of formed inhibition zones by agar well diffusion test and determination of cells growth in presence of studied materials.Item CYTOTOXICITY OF COPPER DOPED SiO2-HYDROXYPROPYL CELLULOSE COMPOSITES ON CANCER AND NON-CANCEROUS CELLS(2023-01-01) Foteva T.; Vukova T.; Rangelova N.; Georgieva N.; Tzoneva R.In the present paper the cytotoxicity of series of sol-gel based copper doped SiO2/HPC composites on lung cancer cell line (A549) and primary human umbilical cord endothelial cells (HUVEC) was investigated. Hydroxypropyl cellulose (HPC), tetraethyl ortosilicate (TEOS) were used for preparation of amorphous matrix in which the copper was added as Cu(NO3)2*3H2O or CuSO4*5H2O in concentration range of 0 - 5 wt. %. We observed that the composite materials at low concentration of Cu (0.5 wt. %) showed no toxic effects on both cell types. The composite material with CuSO4*5H2O was found relatively more toxic, and furthermore, cancer cells are more sensitive to the copper concentration increase to non-cancer cells. The concentration of Cu ions of 2.5 and 5 wt. % were toxic to both cancer and non-cancer cells at 24th hour. At 72th hour of incubation some restoration of cell viability was observedItem DETERMINATION OF SOME PROHIBITED SUBSTANCES IN FOOD SUPPLEMENTS USING HPLC WITH MS OR UV DETECTION - VIEW ON CURRENT DEVELOPMENT(2021-01-01) Zaharieva Z.; Foteva T.; Karadjova V.; Danalev D.Nowadays bioanalytical techniques including liquid and gas chromatography combined with different types of detectors are largely introduced in a practice. They are largely used for detection and control of substances and for monitoring of the whole production process. The type of detector depends on necessary levels of detection, but also on the matrix where aimed compounds have to be determined. Herein are summarized data from the last ten years related to determination of six main prohibited substances sildenafil, tadalafil, vardenafil, dapoxetine, yohimbine and sibutramine as well as their derivatives in food supplements using high performance liquid chromatography combined with mass spectrometric or UV detection. All these compounds are in a large interest because they are introduced often in products freely distributed in the internet market.Item Development and validation of HPLC-DAD methodology for simultaneous qualitative and quantitative determination of thirteen substances with a steroid structure(2023-01-01) Zaharieva Z.; Atanasova S.; Danalev D.; Jaber S.; Foteva T.; Nemska V.; Tanev D.; Georgieva N.Using supplements in different sports is a common practice for many athletes. Unfortunately, the growth of this market has entailed some speculations, such as the addition of excessive doses of potentially toxic ingredients. Sometimes the doses listed on the package do not correspond to the real content. Some nutritional supplements on sale may contain undeclared ingredients. Some of those supplements are prohibited substances according to different regulations. Herein, a simple HPLC/DAD procedure that is easy to apply in conventional laboratory practice was developed for the simultaneous determination of 13 substances with steroid structure in nutritional supplements for sport: testosterone, testosterone propionate, testosterone enanthate, methyltestosterone, nandrolone, nandrolone propionate, nandrolone decanoate, methandienone, androstenedione, trenbolone, trenbolone acetate, trenbolone enanthate and boldenone undecylenate. The methodology includes gradient elution with mobile phase A: MeOH:ddH2O (55:45) and mobile phase B: 100% MeOH in a standard HPLC system containing a Halo 90 Å, C18 (150 x 4.6 mm, 2.7 µm) column, flow rate 0.6 mL/min, UV wavelength of 254 nm, temperature of 40 °C and 20 μL injection volume. The developed methodology was validated according to the corresponding official documents. The key parameters used for the selection of the optimal HPLC conditions were the ability of the mobile phase and solvents to be used with both an HPLC/MS and a GC/MS chromatographic system. The obtained total run time, the reproducibility of the retention times, the separation of all peaks and peak characteristics meet all requirements.Item Effect of B2O3 on the Structure, Properties and Antibacterial Abilities of Sol-Gel-Derived TiO2/TeO2/B2O3 Powders(2023-10-01) Bachvarova-Nedelcheva A.; Iordanova R.; Stoyanova A.; Georgieva N.; Nemska V.; Foteva T.This paper studies the influence of B2O3 on the structure, properties and antibacterial abilities of sol-gel-derived TiO2/TeO2/B2O3 powders. Titanium(IV) butoxide, telluric(VI) acid and boric acid were used as precursors. Differences were observed in the degree of decomposition of Ti butoxide in the presence of H3BO3 and H6TeO6 acids. The phase transformations of the obtained gels in the temperature range of 200–700 °C were investigated by XRD. Composite materials containing an amorphous phase and different crystalline phases (metallic Te, α-TeO2, anatase, rutile and TiTe3O8) were prepared. Heating at 400 °C indicated a crystalline-to-amorphous-phase ratio of approximately 3:1. The scanning electron microscopy (SEM) analysis showed the preparation of plate-like TiO2 nanoparticles. The IR results showed that the short-range order of the amorphous phases that are part of the composite materials consists of TiO6, BO3, BO4 and TeO4 structural units. Free B2O3 was not detected in the investigated compositions which could be related to the better connectivity between the building units as compared to binary TiO2/B2O3 compositions. The UV-Vis spectra of the investigated gels exhibited a red shift of the cut-off due to the presence of boron and tellurium units. The binary sample achieved the maximum photodegradation efficiency (94%) toward Malachite green dye under UV irradiation, whereas the ternary sample photoactivity was very low. The compositions exhibited promising antibacterial activity against E. coli NBIMCC K12 407.Item INFLUENCE OF Nb2O5 AND B2O3 ON THE PHOTOCATALYTIC AND ANTIBACTERIAL ACTIVITY OF SOL-GEL DERIVED TiO2 NANOPОWDERS(2024-01-01) Bachvarova-Nedelcheva A.; Iordanova R.; Georgieva N.; Nemska V.; Foteva T.; Stoyanova A.TiO2 based powders containing B2O3 and Nb2O5 were obtained through an aqueous sol-gel method. The as-prepared gels were step wisely heated in the temperature range 200°C - 500°C and subsequently characterized by XRD, IR and UV-Vis analysis. The TiO2 (anatase) is the single crystalline phase which has been detected up to 500°C. Photocatalytic tests showed that the investigated samples possess photocatalytic activity toward Malachite green organic dye and TiO2/Nb2O5 exhibited higher photocatalytic activity than TiO2/B2O3 sample. The compositions exhibited good antimicrobial activity against E. coli NBIMCC K12 407 and Bacillus subtilis NBIMCC 3562.Item NANOTECHNOLOGY IN THE COSMETIC INDUSTRY (REVIEW)(2024-01-01) Foteva T.Nanotechnology has been increasingly explored and utilized in the cosmetic industry to enhance the efficacy and performance of cosmetic products. The incorporation of nanomaterials in cosmetics presents both advantages and challenges. As a positive effect can be noted that nanotechnology offers the potential to improve the performance, retention, appearance, and safety of cosmetic formulations, meeting the demands of customers for better cosmetic products. Nanoparticles are used in cosmetics to enhance the delivery of active ingredients, improve the appearance and feel of products, and serve as UV filters, demonstrating the diverse applications of nanotechnology in cosmetic products. However, it also presents challenges related to safety, health risks, and regulatory considerations, highlighting the need for ongoing research, safety assessments, and regulatory frameworks to ensure the safe and effective use of nanotechnology in cosmetics.Item SILVER NANOPARTICLES INCORPORATED INTO POROUS COLLAGEN SCAFFOLDS(2022-01-01) Samichkov V.; Mladenova B.; Diankov S.; Foteva T.; Hinkov I.In this work, we present a simple, rapid and cost-effective microwave-assisted method for silver nanoparticles synthesis by chemical reduction using an aqueous solution of silver nitrate, ethanol and ammonia. The effect of reagent concentrations and the heating time was investigated. Samples were analyzed through UV-Vis spectroscopy and transmission electron microscopy. Furthermore, the obtained silver nanoparticles were mixed with collagen dispersions to prepare porous scaffolds by vacuum-sublimation drying. Silver nanoparticles can adhere to the bacterial cell wall subsequently causing its death. The microbiological study showed that the collagen scaffolds with incorporated silver nanoparticles exhibited antibacterial activity against Bacillus subtilis NBIMCC 3562 and Escherichia coli NBIMCC 407 bacteria and could find potential applications in medicine.Item Sol-Gel Obtaining of TiO2/TeO2 Nanopowders with Biocidal and Environmental Applications(2023-02-01) Bachvarova-Nedelcheva A.; Iordanova R.; Naydenov A.; Stoyanova A.; Georgieva N.; Nemska V.; Foteva T.TiO2/TeO2 powders were obtained by an aqueous sol-gel method. Telluric acid (H6TeO6) and titanium butoxide were used as precursors. The as-prepared gel was step-wisely heated in the temperature range 200–700 °C and subsequently characterized by XRD, IR, and UV-Vis analysis and SEM. Mixtures containing TiO2 (anatase), α-TeO2 (paratellurite), and TiTe3O8 were established by XRD as final products, depending on heating temperature. The thermal stability of the obtained gels in the temperature range 100–400 °C was investigated. It was found by IR spectroscopy that the samples heated up to 300–400 °C consist mainly of an organic–inorganic amorphous phase which is transformed into an inorganic one above these temperatures. The microstructure of the gels was verified by scanning electron microscopy (SEM). The photocatalytic degradation of the synthesized nanopowders toward Malachite green organic dye (MG) was examined in order to evaluate the potential applications for environmental remediation. The prepared TiO2/TeO2 samples showed up to 60% decoloration efficiency after 120 min exposure to UV-light. The composition exhibited good antimicrobial activity against E. coli K12. The properties of the obtained material were investigated by the reactions of complete catalytic oxidation of different alkanes and toluene, and it could be suggested that TiO2/TeO2 powders are promising material for use as an active phase in environmental catalysts.Item Synthesis and Biological Studies of New Temporin A Analogs Containing Unnatural Amino Acids in Position 7(2024-06-01) Dimitrova D.; Nemska V.; Foteva T.; Iliev I.; Georgieva N.; Danalev D.(1) Background: Antimicrobial resistance is growing at an extreme pace and has proven to be an urgent topic, for research into alternative treatments. Such a prospective possibility is hidden in antimicrobial peptides because of their low to no toxicity, effectiveness at low concentrations, and most importantly their ability to be used for multiple treatments. This work was focused on the study of the effect of the modification in position 7 of Temporin A on its biological activity; (2) Methods: The targeted peptides were synthesized using Fmoc/Ot-Bu SPPS. The antibacterial activity of the analogs was determined using the broth microdilution method and disk-diffusion method. In vitro tests were performed to determine the cytotoxicity, phototoxicity, and antiproliferative activity of the peptide analogs on a panel of tumor and normal cell lines; (3) Results: All analogs except DTCit showed good antibacterial activity, with DTDab having the best activity according to the disk-diffusion method. However, DTCit had an acceptable cytotoxicity, combined with good selectivity against the test MCF-7 cell line; (4) Conclusions: The obtained results revealed the importance of the basicity and length of the side chain at position 7 in the Temporin A sequence for both tested activities.Item Synthesis and biological studies on (KLAKLAK)2-NH2 analog containing unnatural amino acid β-ala and conjugates with second pharmacophore(2021-12-01) Jaber S.; Nemska V.; Iliev I.; Ivanova E.; Foteva T.; Georgieva N.; Givechev I.; Naydenova E.; Karadjova V.; Danalev D.(1) Background: Peptides are good candidates for anticancer drugs due to their natural existence in the body and lack of secondary effects. (KLAKLAK)2 is an antimicrobial peptide that also shows good anticancer properties. (2) Methods: The Solid Phase Peptide Synthesis (Fmoc-strategy) was used for the synthesis of target molecules, analogs of (KLAKLAK)2-NH2. The purity of all compounds was monitored by HPLC, and their structures were proven using mass spectrometry. Cytotoxicity and antiproliferative effects were studied using 3T3 NRU and MTT tests, respectively. For determination of antimicrobial activity, the disc-diffusion method was used. Hydrolytic stability at three pH values, which mimic the physiological pH in the body, was investigated by means of the HPLC technique. (3) Results: A good selective index against MCF-7 tumor cell lines, combined with good cytotoxicity and antiproliferative properties, was revealed for conjugates NphtG-(KLAKLAK)2-NH2 and Caf-(KLAKLAK)2-NH2. The same compounds showed very good antifungal properties and complete hydrolytic stability for 72 h. The compound Caf-(KLβ-AKLβ-AK)2-NH2 containing β-Ala in its structures exhibited good antimicrobial activity against Escherichia coli K12 407 and Bacillus subtilis 3562, in combination with very good antiproliferative and cytotoxic properties, as well as hydrolytic stability. (4) Conclusions: The obtained results reveal that all synthesized conjugates could be useful for medical practice as anticancer or antimicrobial agents.Item Synthesis, antiproliferative and antimicrobial activities of (KLAKLAK)2-NH2 analogue containing nor-Leu and its conjugates with a second pharmacophore(2023-01-01) Jaber S.; Nemska V.; Iliev I.; Ivanova E.; Foteva T.; Georgieva N.; Givechev I.; Tanev D.; Naydenova E.; Danalev D.Peptides are a promising alternative of conventional medical drugs for the treatment of different diseases because they have no or have very few side effects owing to the natural mechanisms for their elimination. There are a lot of examples of drugs on the pharmaceutical market based on modified amino acids and peptides. Herein, we report the synthesis and studies on the antimicrobial peptide (KLAKLAK)2-NH2 where Leu is replaced by the unnatural amino acid nor-Leu. In addition, a second pharmacophore with well proven anticancer properties is introduced to the peptide moiety. All structures were synthesized by conventional solid phase peptide synthesis. The antiproliferative and antimicrobial activities were studied using MTT-dye reduction assay and disk-diffusion test, respectively. Biological activity assays showed that the introduction of nor-Leu in the primary structure of the parent compound does not lead to an increase in the antiproliferative activity. However, the combination with the second pharmacophore 1,8-naphtalimide in a hybrid structure 1,8-NphtG-(KNleAKNleAK)2-NH2 leads to a significant increase in the antiproliferative properties. The antimicrobial tests showed that all tested compounds exhibit antimicrobial activity. The peptide and the second pharmacophore had a synergistic effect. In combination with complete hydrolytic stability for 72 h in model systems, the compound 1,8-NphtG-(KNleAKNleAK)2-NH2 is the best candidate for a medical drug in the treatment of mammary gland type A adenocarcinoma (MCF-7) in combination with antimicrobial properties.