Browsing by Author "Vasileva-Tonkova E."
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Item A new bioactive complex between zn(II) and a fluorescent symmetrical benzanthrone tripod for an antibacterial textile(2019-11-01) Staneva D.; Vasileva-Tonkova E.; Grabchev I.A new fluorescent Zn(II) complex of symmetrical tripod form based on a 3-substituted benzanthrone (BT) has been synthesized and characterised. The basic photophysical properties of the new metal complex have been determined. It has been found by fluorescence spectroscopy that, one zinc ion forms a complex with the tripod ligand. The surface morphology of the ligand and its Zn(II) complex has been investigated by the scanning electron microscopy (SEM) technique. X-ray photoelectron spectroscopy (XPS) has been used for the characterisation of the chemical composition of the complex surfaces. The antibacterial activity of the Zn(II) complex has been investigated in solution and upon its deposition onto a cotton fabric. A reduction of biofilm formation on the surface of the cotton fabric has been observed compared to the non-treated cotton material. The results obtained demonstrate that the studied Zn(II) complex possesses good antimicrobial activity being most effective against the used Gram-positive bacteria.Item A new cu(Ii) complex of pamam dendrimer modified with 1,8-naphthalimide: Antibacterial and anticancer activity(2022-08-15) Manov H.; Staneva D.; Vasileva-Tonkova E.; Kukeva R.; Stoyanov S.; Grabchev I.; Alexandrova R.; Stoyanova R.A new fluorescent PAMAM copper complex ([Cu2 (D)(NO3 )4 ]) has been synthesized and identified. The formation of the complex has been investigated by fluorescence spectroscopy which revealed two copper ions to be bound to the dendrimer ligand. That has also been confirmed upon subjecting the solid copper complex to electron paramagnetic spectroscopy. The antimicrobial activity of the copper complex against Gram-negative bacterium Pseudomonas aeruginosa in light and the dark has been studied. The results demonstrate an increase in its activity when irradiated with daylight. This activity of the copper complex is retained even after being loaded onto a cotton cloth. The antitumor activity of the copper complex and dendrimer ligand against triple-negative breast cancer MDA-MB-231 cells has been investigated as well.Item Cotton fabric modified with a pamam dendrimer with encapsulated copper nanoparticles: Antimicrobial activity(2021-12-01) Staneva D.; Atanasova D.; Nenova A.; Vasileva-Tonkova E.; Grabchev I.A new methodology for modifying textile materials with dendrimers containing nanoparticles was developed. This involved a combination of eosin Y and N-methyldiethanolamine (MDEA) for reducing the copper ions in the dendrimer complex by enabling a photochemical reaction under visible light and ambient conditions. The conversion of copper ions into nanoparticles was monitored using scanning electron microscopy (SEM) and by performing colorimetric, fluorescence, and electron paramagnetic resonance (EPR) studies. Regardless of the concentration of the photoinitiator eosin Y, it discolored completely upon illumination. Three types of cotton fabrics were compared as antimicrobial materials against Bacillus cereus. One of the fabrics was dyed with a first-generation PAMAM dendrimer which had been functionalized with eight 1,8-naphthalimide fluorophores. Another fabric was dyed with a dendrimer–copper complex, and the third was treated by conversion of the complex into copper nanoparticles encapsulated into the dendrimer. An enhancement in the antimicrobial activity of the textiles was achieved at higher dendrimer concentrations, under illumination with visible light. The fabric modified with the copper nanoparticles encapsulated inside the dendrimer exhibited the best antibacterial activity because it had two photosensitizers (PS), as both 1,8-naphthalimide fluorophores and copper nanoparticles were contained in the dendrimer molecules. The presence of oxygen and suitable illumination activated the photosensitizers to generate the reactive oxygen species (singlet oxygen (1O2) and other oxygenated products, e.g., anion radicals, hydroxyl radicals, and hydrogen peroxide) responsible for destroying the bacteria.Item Enhanced Photodynamic Efficacy Using 1,8-Naphthalimides: Potential Application in Antibacterial Photodynamic Therapy(2022-09-01) Staneva D.; Said A.I.; Vasileva-Tonkova E.; Grabchev I.This study addresses the need for antibacterial medication that can overcome the current problems of antibiotics. It does so by suggesting two 1,8-naphthalimides (NI1 and NI2) containing a pyridinium nucleus become attached to the imide-nitrogen atom via a methylene spacer. Those fluorescent derivatives are covalently bonded to the surface of a chloroacetyl-chloride-modified cotton fabric. The iodometric method was used to study the generation of singlet oxygen (1O2) by irradiation of KI in the presence of monomeric 1,8-naphthalimides and the dyed textile material. Both compounds generated reactive singlet oxygen, and their activity was preserved even after they were deposited onto the cotton fabric. The antibacterial activity of NI1 and NI2 in solution and after their covalent bonding to the cotton fabric was investigated. In vitro tests were performed against the model gram-positive bacteria B. cereus and gram-negative P. aeruginosa bacteria in dark and under light iradiation. Compound NI2 showed higher antibacterial activity than compound NI1. The light irradiation enhanced the antimicrobial activity of the compounds, with a better effect achieved against B. cereus.Item Hyperbranched polymers modified with Dansyl units and their Cu(II) complexes. bioactivity studies(2020-10-02) Bosch P.; Staneva D.; Vasileva-Tonkova E.; Grozdanov P.; Nikolova I.; Kukeva R.; Stoyanova R.; Grabchev I.Two new copper complexes of hyperbranched polymers modified with dansyl units were synthesized and characterized by infrared spectroscopy (IR) and electron paramagnetic resonance (EPR) techniques. It was found that copper ions coordinate predominantly with nitrogen or oxygen atoms of the polymer molecule. The place of the formation of complexes and the number of copper ions involved depend on the chemical structure of the polymer. The antimicrobial activity of the new polymers and their Cu(II) complexes was tested against Gram-negative and Gram-positive bacterial and fungal strains. Copper complexes were found to have activity better than that of the corresponding ligands. The deposition of the modified branched polymers onto cotton fabrics prevents the formation of bacterial biofilms, which indicates that the studied polymers can find application in antibacterial textiles.Item New Poly(Propylene Imine) dendrimer modified with acridine and its Cu(II) complex: Synthesis, characterization and antimicrobial activity(2019-09-01) Bosch P.; Staneva D.; Vasileva-Tonkova E.; Grozdanov P.; Nikolova I.; Kukeva R.; Stoyanova R.; Grabchev I.A second-generation poly(propylene imine) dendrimer modified with acridine and its Cu(II) complex have been synthesized for the first time. It has been found that two copper ions form complexes with the nitrogen atoms of the dendrimeric core by coordinate bonds. The new compounds have been characterized by nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), fourier-transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. The spectral characteristics of the modified dendrimer have been measured in different organic solvents, and a negative fluorescence solvatochromism has been observed. The antimicrobial activity of the dendrimers has been tested against model pathogenic microorganisms in agar and by broth dilution method. The cotton fabric treated with both dendrimers has been evaluated towards pathogenic microorganisms. The obtained modified cotton fabrics have been shown to hamper bacterial growth and to prevent biofilm formation. Dendrimer cytotoxicity has been investigated in vitro in the model HEp-2 cell line.Item Photophysical and antibacterial activity of light-activated quaternary eosin Y(2019-01-01) Staneva D.; Yordanova S.; Vasileva-Tonkova E.; Stoyanov S.; Grabchev I.The functional characteristics of a new eosin dye with biocidal quaternary ammonium group (E) were studied in aqueous solution and in organic solvents of different polarity. The spectral properties depend on the nature and polarity of the respective solvents. The antimicrobial activity of compound E has been tested in vitro against Gram-negative bacteria (Escherichia coli, Acinetobacter johnsoni and Pseudomonas aeruginosa), Gram-positive bacteria (Sarcina lutea and Bacillus cereus) and the antifungal activity was tested against the yeasts Candida lipolytica in solution and after treated on cotton fabric. Broth dilution test has been used for quantitative evaluation of the antimicrobial activity of compound E against the model strains. The ability of compound E to inhibit the growth of model Gram-negative P. aeruginosa strain was assessed after 16 h of incubation in presence and absence of light. These experiments were conducted in planktonic format in solution and on cotton fabric. The results suggest that the new compound is effective in treating the relevant pathogens with better results being obtained by irradiation with light. In this case the quaternary ammonium group promotes the binding of eosin Y moiety to the bacterial cell wall thus accelerating bacterial photo inactivation.Item Study of Novel Peptides for Antimicrobial Protection in Solution and on Cotton Fabric(2022-08-01) Todorov P.; Georgieva S.; Staneva D.; Peneva P.; Grozdanov P.; Nikolova I.; Vasileva-Tonkova E.; Grabchev I.Some new N- and C-modified biomolecular peptide analogues of both VV-hemorphin-5 and VV-hemorphin-7 with varied amino acids (Cys, Glu, His), 1-adamantanecarboxylic acid, and niacin (nicotinic acid) were synthesized by solid-phase peptide synthesis—Fmoc (9-fluorenylmethoxy-carbonyl) chemistry and were characterized in water solutions with different pH using spectroscopic and electrochemical techniques. Basic physicochemical properties related to the elucidation of the peptide structure at physiological pH have been also studied. The results showed that the interaction of peptide compounds with light and electricity preserves the structural and conformational integrity of the compounds in the solutions. Moreover, textile cotton fibers were modified with the new compounds and the binding of the peptides to the surface of the material was proved by FTIR and SEM analysis. Washing the material with an alkaline soap solution did not show a violation of the modified structure of the cotton. Antiviral activity against the human respiratory syncytial virus (HRSV-S2) and human adenovirus serotype 5 (HAdV-5), the antimicrobial activity against B. cereus and P. aeruginosa used as model bacterial strains and cytotoxic effect of the peptide derivatives and modified cotton textile material has been evaluated. Antimicrobial tests showed promising activity of the newly synthesized compounds against the used Gram-positive and Gram-negative bacteria. The compounds C-V, H-V, AC-V, and AH-V were found slightly more active than NH7C and NCH7. The activity has been retained after the deposition of the compounds on cotton fibers.Item Surface functionalization of cotton fabric with fluorescent dendrimers, spectral characterization, cytotoxicity, antimicrobial and antitumor activity(2019-06-01) Grabchev I.; Staneva D.; Vasileva-Tonkova E.; Alexandrova R.Poly(propylenimine) dendrimers from first and third generations modified with 1,8-naphthalimide units and their Zn(II) complexes have been investigated by absorption and fluorescence spectroscopy. These dendrimers have been deposited on a cotton cloth by the extraction method, producing yellow-colored textile materials. They have been characterized by defining their color coordinates L*a*b*, XYZ and xy. The antimicrobial activity of dendrimers has been investigated in vitro against model gram-positive and gram-negative bacteria and yeasts. Being deposited onto the surface of cotton fabric, the studied dendrimers reduced bacterial growth and prevented the formation of bacterial biofilm. Anticancer and cytotoxicity activities have also been performed against HeLa and Lep-3 human tumor cell lines as model systems.Item Synthesis, Spectral Characteristics, Sensing Properties and Microbiological Activity of New Water-Soluble 4-Sulfo-1,8-naphthalimides(2024-05-01) Said A.I.; Staneva D.; Vasileva-Tonkova E.; Grozdanov P.; Nikolova I.; Stoyanova R.; Jordanova A.; Grabchev I.A new water-soluble polyamidoamine (PAMAM) dendrimer modified with 4-sulfo-1,8-naphthalimide (DSNI) and its monomeric structural analogue (MSDI) were synthesized. Their photophysical properties were investigated in organic solvents of different polarities and aqueous solutions. The effect of pH on fluorescence intensity was determined. It was found that the dendrimer emits blue fluorescence in an acidic medium, which is quenched in an alkaline environment. This phenomenon is due to the possibility of suppression of nonradiative photoinduced electron transfer in acidic media. The influence of different metal ions (Cu2+, Pb2+, Sn2+, Sr2+, Mg2+, Ba2+, Co2+, Hg2+, Zn2+, Ni2+, Fe3+, Al3+) and anions (CN−, S2−, S2O52−, HPO42−, H2PO4−, F−, CH3COO−, NO2−, CO32−, SO42−) on the intensity of the emitted fluorescence was studied. Quenching was only found in the presence of Cu2+. This makes the dendrimer suitable for determining copper ions in water solutions in the presence of other metal ions and anions. Additionally, DSNI was used as a ligand to obtain a stable copper complex, the structure of which was investigated by electron paramagnetic resonance (EPR), infrared spectrum, and elemental analysis. Two copper ions were found to form a complex with one dendrimer. The in vitro microbiological activity of the new compounds against bacteria Pseudomonas aeruginosa and two viruses HRSV-2 and HAdV-5 was investigated. With a view to obtaining antibacterial and anti-viral textiles, cotton fabrics were treated with the three compounds, and then their activity against the same microbial strains was investigated. It was found that the microbiological activity was preserved after the application of the new compounds to the cotton fabrics.