Browsing by Author "Angelova T."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item ANTIBACTERIAL ACTIVITY AND STRUCTURE OF SOL-GEL BASED SiO2/HPC/Zn NANOCOMPOSITES(2020-01-01) Angelova T.; Rangelova N.; Aleksandrov L.; Georgieva N.The present paper reports an investigation of the antibacterial activity of sol-gel derived silica/hydroxypropyl cellulose zinc doped nanocomposites. The thermal analysis shows that the crosslinking between cellulose ether and zinc ions is more thermally stable than the crosslinking of the precursors in the matrix. The optical investigation and the transmission electron microscopy (TEM) observation verify the existence of nano-dimentional zinc particles. The antibacterial properties of the composites are investigated by measuring the inhibition zones formed around the materials of a different zinc content in presence of reference strains of Gram-positive bacteria - Bacillus subtilis 3562 and Gram-negative bacteria - Escherichia coli K12 and by calculating the growth decrease percentage.Item Antibacterial activity of SiO 2/hydroxypropyl cellulose hybrid materials containing silver nanoparticles(2012-07-01) Angelova T.; Rangelova N.; Yuryev R.; Georgieva N.; Müller R.Silica hybrid materials containing tetraethyl orthosilicate (TEOS) as SiO 2 precursor, hydroxypropyl cellulose (HPC) as an organic compound with incorporation of silver were prepared, and their structure and surface morphology were examined by FTIR measurements and SEM. The quantity of organic substance was 5 wt.% and the silver concentration varied from 0.5 to 2.5 wt.%. It is suggested that the main structural units build an amorphous network of synthesized hybrids from depolymerized [SiO 4] tetrahedra giving strong bands at 1050 and 790 cm - 1. The surface morphology changed from smooth to rough with the increasing amount of silver. The possible antibacterial behavior of the hybrid materials was also studied. The results indicate pronounced antibacterial performance against Escherichia coli and Bacillus subtilis. Highest antibacterial activity was detected against B. subtilis. The increase of silver concentration up to 2.5 wt.% Ag leads to stronger antibacterial effects with both strains. © 2012 Elsevier B.V. All rights reserved.Item Antifungal effect of SiO2/cellulose ethers/Ag hybrid nanomaterials on the growth of Penicillium chrysogenum 2303(2016-01-01) Angelova T.; Mohamed R.A.A.E.; Rangelova N.; Georgieva N.Three types of silica hybrid nanomaterials, doped with silver, were studied for their antifungal effect against fungi Penicillium chrysogenum strain 2303. The hybrid nanomaterials based on SiO2 and cellulose ethers - hydroxypropyl cellulose, hydroxypropylmethyl cellulose and carboxymethyl cellulose, and silver were prepared by sol-gel method. The antifungal effect was quantified against P. chrysogenum 2303 based on the inhibition zone measurement by the agar diffusion test. The results showed that the hybrid nanomaterials containing hydroxypropylmethyl cellulose, doped with the highest silver concentration of 2.5 mass % Ag, have the most prominent antifungal effect towards the fungi in comparison to the other nanomaterials.Item ANTIMICROBIAL ACTIVITY OF AMINO ACID DERIVATIVES OF MEMANTINE(2022-01-01) Tencheva A.; Stankova I.; Angelova T.; Nemska V.; Georgieva N.; Danalev D.Memantine is adamantane derivative used in medicinal practice. It is well-proven inhibitors of the M2 ion channel of influenza virus. In addition, it is applied for treatment of patients with Alzheimer’s disease. Herein, we report the antimicrobial activity of specifically designed memantine derivatives containing spatially compact (Gly, Ala, β-Ala) and bulky (Val and Phe) amino acids. New compounds were synthesized in a solution using 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU) as a coupling agent. All derivatives were obtained with good yields. Newly synthesized molecules at concentration 100 mM were tested for their antimicrobial activity using model strains of Gram-positive (Bacillus subtilis NBIMCC 3562), Gram-negative (Escherichia coli NBIMCC K12 407) microorganisms and fungal strain Candida albicans NBIMCC 74. The active compounds against model G+ microorganism are Val-MEM followed by Ala-MEM and Gly-MEM. All compounds show good activity against model G-microorganism. Introducing of bulky amino acid Phe, containing aromatic core, and Val, containing aliphatic core, leads to good antifungal activityItem Antimicrobial activity of SiO2/cellulose ethers/Ag hybrid materials against Saccharomyces cerevisiae 537(2016-01-01) Angelova T.; Georgieva N.; Müller R.The antimicrobial effect against Saccharomyces cerevisiae 537 of silica hybrid materials based on tetraethylorthosilicate, cellulose derivates (hydroxypropyl cellulose and hydroxypropyl methyl cellulose) and silver was investigated. The silver concentration in the hybrid materials varied from 0.5 wt % to 2.5 wt %. The antimicrobial effect was quantified on ground of the inhibition zone measurement and determination of the growth of the synthesized hybrid materials inhibitory effect. The results showed 80 % and 92 % decrease of cell growth by hydroxypropyl cellulose hybrid materials and hydroxypropyl methyl cellulose, respectively, in presence of the highest silver concentration of 2.5 wt %. The lowest silver concentration of 0.5 wt % Ag had no effect on the tested strain viability as the cells observed were not inactivated.Item BIOCOMPATIBILITY AND ANTIFUNGAL ACTIVITY OF SILVER DOPED SiO2/PECTIN COMPOSITE MATERIALS(2021-01-01) Angelova T.; Uzunova V.; Rangelova N.; Georgieva N.; Momchilova A.; Tzoneva R.The purpose of the study was to evaluate the biocompatibility and antifungal activity of silver doped SiO2/citrus pectin composite materials. The effect of the amount of silver content (0 - 2.5 wt. %) on biocompatibility using L929 fibroblast cells and antifungal activity against Candida albicans 74 was observed. It was established that composites containing 0.5 wt. % and 1 wt. % Ag exhibited biocompatibility as well as revealed low cytotoxicity, good cell adhesion and spreading and luck of apoptosis. The antifungal activity of the composites demonstrated that the size of formed inhibition zones depends on the amount of silver in the materials. Based on the obtained results, silver doped SiO2/ pectin composite materials were proven to be efficient for use as in vivo implants in tissue engineering applications.Item Cytotoxicity and antibiofilm activity of SiO2/cellulose derivative hybrid materials containing silver nanoparticles(2016-01-01) Angelova T.; Rangelova N.; Uzunova V.; Georgieva N.; Andreeva T.; Momchilova A.; Tzoneva R.; Müller R.Hybrid materials based on tetraethyl orthosilicate (TEOS), hydroxypropyl cellulose (HPC), or hydroxypropyl methyl cellulose (HPMC) with silver nanoparticles were synthesized. They were analyzed and characterized using differential thermal analysis and thermogravimetry, atomic force microscopy, and static contact angle measurements. It was experimentally demonstrated that the silverdoped hybrid materials have pronounced antibacterial behavior by studying the reduction of Pseudomonas aeruginosa PAO1 biofilm formation on the tested materials. The results revealed biofilm reduction of 35.7% and 30% by SiO2/HPC/2.5% Ag and SiO2/HPMC/2.5% Ag hybrid materials, respectively, compared to the control. Cytotoxicity of examined materials and actin cytoskeleton organization of fibroblasts seeded on the materials was studied as a function of material properties as the type of surface functional groups and silver content. The obtained hybrid materials with low silver content proved efficient in tissue engineering applications since they showed good antibacterial and noncytotoxic properties for eukaryotic cells.Item Synthesis, antitumor and antibacterial studies of new shortened analogues of (KLAKLAK)2-NH2 and their conjugates containing unnatural amino acids(2021-02-02) Jaber S.; Iliev I.; Angelova T.; Nemska V.; Sulikovska I.; Naydenova E.; Georgieva N.; Givechev I.; Grabchev I.; Danalev D.(1) Background: (KLAKLAK)2 is a representative of the antimicrobial peptide group which also shows good anticancer properties. (2) Methods: Herein, we report synthesis using SPPS and characterization by HPLC/MS of a series of shortened analogues of (KLAKLAK)2. They contain single sequence KLAKLAK as C-terminal amides. In addition, substitution of some natural amino acids with unnatural β-Ala and nor-Leu is realized. In addition, these structures are conjugated with second pharmacophore with well proven anticancer properties 1,8-naphthalimide or caffeic acid. Cytotoxicity, antiproliferative effect and antimicrobial activity of newly synthesized structures were studied. (3) Results: The obtained experimental results reveal significant selective index for substances with common chemical structure KLβAKLβAK-NH2. The antibacterial properties of newly synthesized analogues at two different concentrations 10 μM and 20 μM, were tested against Gram-negative microorganisms Escherichia coli K12 407. Only two of the studied compounds KLAKLAK-NH2 and the one conjugated with second pharmacophore 1,8-naphthalimide and unnatural amino acid nor-Leu showed moderate activity against tested strains at concentration of 20 μM. (4) Conclusions: The obtained results reveal that the introducing of 1,8-naphthalimideGlyand Caf- increase the cytotoxicity and antiproliferative activity of the peptides but not their selectivity. Only two compounds KLAKLAK-NH2 and 1,8-naphthalimideGKnLAKnLAK-NH2 show moderate activity against Escherichia coli K12 at low concentration of 20 μM.Item Synthesis, Characterization and antibacterial assessment of sio2-hydroxypropylmethyl cellulose hybrid materials with embedded silver nanoparticles(2014-10-22) Angelova T.; Rangelova N.; Dineva H.; Georgieva N.; Müller R.Antibacterial SiO2 hybrid materials based on tetraethyl orthosilicate (TEOS), hydroxypropylmethylcellulose (HPMC) and silver were prepared by the sol-gel method. The content of cellulose derivate was 5 wt% and the silver concentration varied from 0.5 wt% to 2.5 wt%. The amorphous nature, morphology and antibacterial behaviour were studied. Fourier transform infrared (FTIR) spectra of the hybrids showed characteristic peaks for SiO2 network. Scanning electron microscope (SEM) analysis confirmed the formation of spherically shaped silver nanoparticles with a size of 30 nm on the matrix surfaces. Bacillus subtilis and Escherichia coli K12 were used as model microorganisms. The hybrid materials demonstrated bacteriostatic and bactericidal effect on the tested bacteria. Highest sensitivity to the obtained hybrids was observed in B. subtilis with significant lag-phase delay and biggest inhibition zone sizes.