Browsing by Author "Georgiev N."
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Item A novel 1,8-naphthalimide probe for selective determination of Hg2+ in a wide pH window(2018-01-01) Krasteva P.; Dimitrova M.; Georgiev N.; Bojinov V.This paper reports the synthesis and photophysical investigation of a novel 1,8-naphthalimide fluorophore containing 2-amino-1,3,4-thiadiazole fragment at C-4 position. Absorption and fluorescence characteristics of the dye as a function of pH were investigated in water/ethanol (1:1, v/v) solution. It was found that the synthesized 1,8-naphthalimide did not show significant changes in the emission properties in a wide pH range. Furthermore the ability of the synthesized compound to detect cations was evaluated by the changes in its fluorescence intensity in the presence of metal ions (Co2+, Cu2+, Fe3+, Ni2+, Pb2+, Cd2+, Zn2+ and Hg2+). Only Hg2+, among the tested metal ions, was efficiently detected due to the aggregation caused quenching process. The results obtained indicate the potential of the novel compound acting as a fluorescent ``onoff`` switch for selective determination of Hg2+ in a wide pH window.Item Eu3+ doped glasses in the Bi2O3-B2O3-WO3-Al2O3 system(2015-01-01) Aleksandrov L.; Iordanova R.; Khanna A.; Georgiev N.; Dimitriev Y.The structure of many Eu3+ doped Bi2O3-B2O3-WO3-Al2O3 glasses of a different composition is studied using infrared spectroscopic technique (IR). It is found that distorted BiO6 (of a band at 480 cm-1), BO3 (of bands at 1390, 1230, 620 cm-1), BO4 (of a band at 1020 cm-1) and WO4 polyhedra (of a band at 880 cm-1) are the main building units forming the amorphous networks. WO6 groups exist in the glass network of a high WO3 content (of bands at 880 cm-1, 620 cm-1, and a shoulder at 670 cm-1). WO3 does not stimulate formation of BO4 structural units. According to the differential thermal analysis (DTA) the glass transition temperature (Tg) of the investigated glasses is situated in the range of 400°C - 485°C. The DTA curves of all glasses show two exothermic peaks corresponding to the formation of two crystal phases. Photoluminescence emissions due to the 4f transitions 5D0→7Fj (j=0-4) of Eu3+ ions are observed. The addition of WO3 to the glass compositions decreases the emission intensity of investigated glasses.Item Fused Triazinobenzimidazoles Bearing Heterocyclic Moiety: Synthesis, Structure Investigations, and In Silico and In Vitro Biological Activity(2023-07-01) Anichina K.; Georgiev N.; Lumov N.; Vuchev D.; Popova-Daskalova G.; Momekov G.; Cherneva E.; Mihaylova R.; Mavrova A.; Atanasova-Vladimirova S.; Piroeva I.; Yancheva D.[1,3,5]Triazino[1,2-a]benzimidazole-2-amines bearing heterocyclic moiety in 4-position were synthesized. The compounds were characterized by elemental analysis, IR, 1H-NMR, 13C-NMR, and HRMS spectroscopy. The molecular geometry and electron structure of these molecules were theoretically studied using density functional theory (DFT) methods. The molecular structure of the synthesized fused triazinobenzimidazole was confirmed to correspond to the 3,4-dihydrotriazinobenzimidazole structure through the analysis of spectroscopic NMR data and DFT calculations. The antinematodic activity was evaluated in vitro on isolated encapsulated muscle larvae (ML) of Trichinella spiralis. The results showed that the tested triazinobenzimidazoles exhibit significantly higher efficiency than the conventional drug used to treat trichinosis, albendazole, at a concentration of 50 μg/mL. The compound 3c substituted with a thiophen-2-yl moiety exhibited the highest anthelmintic activity, with a larvicidal effect of 58.41% at a concentration of 50 μg/mL after 24 h of incubation. Following closely behind, the pyrrole analog 3f demonstrated 49.90% effectiveness at the same concentration. The preliminary structure-anti-T. spiralis activity relationship (SAR) of the analogues in the series was discussed. The cytotoxicity of the benzimidazole derivatives against two normal fibroblast cells (3T3 and CCL-1) and two cancer human cell lines (MCF-7 breast cancer cells and chronic myeloid leukemia cells AR-230) was evaluated using the MTT-dye reduction assay. The screening results indicated that the compounds showed no cytotoxicity against the tested cell lines. An in silico study of the physicochemical and pharmacokinetic characteristics of the novel synthesized fused triazinobenzimidazoles showed that they were characterized by a significant degree of drug-likeness and optimal properties for anthelmintic agents.Item Fused Triazinobenzimidazoles Bearing Heterocyclic Moiety: Synthesis, Structure Investigations, and In Silico and In Vitro Biological Activity(2023-07-01) Anichina K.; Georgiev N.; Lumov N.; Vuchev D.; Popova-Daskalova G.; Momekov G.; Cherneva E.; Mihaylova R.; Mavrova A.; Atanasova-Vladimirova S.; Piroeva I.; Yancheva D.[1,3,5]Triazino[1,2-a]benzimidazole-2-amines bearing heterocyclic moiety in 4-position were synthesized. The compounds were characterized by elemental analysis, IR, 1H-NMR, 13C-NMR, and HRMS spectroscopy. The molecular geometry and electron structure of these molecules were theoretically studied using density functional theory (DFT) methods. The molecular structure of the synthesized fused triazinobenzimidazole was confirmed to correspond to the 3,4-dihydrotriazinobenzimidazole structure through the analysis of spectroscopic NMR data and DFT calculations. The antinematodic activity was evaluated in vitro on isolated encapsulated muscle larvae (ML) of Trichinella spiralis. The results showed that the tested triazinobenzimidazoles exhibit significantly higher efficiency than the conventional drug used to treat trichinosis, albendazole, at a concentration of 50 μg/mL. The compound 3c substituted with a thiophen-2-yl moiety exhibited the highest anthelmintic activity, with a larvicidal effect of 58.41% at a concentration of 50 μg/mL after 24 h of incubation. Following closely behind, the pyrrole analog 3f demonstrated 49.90% effectiveness at the same concentration. The preliminary structure-anti-T. spiralis activity relationship (SAR) of the analogues in the series was discussed. The cytotoxicity of the benzimidazole derivatives against two normal fibroblast cells (3T3 and CCL-1) and two cancer human cell lines (MCF-7 breast cancer cells and chronic myeloid leukemia cells AR-230) was evaluated using the MTT-dye reduction assay. The screening results indicated that the compounds showed no cytotoxicity against the tested cell lines. An in silico study of the physicochemical and pharmacokinetic characteristics of the novel synthesized fused triazinobenzimidazoles showed that they were characterized by a significant degree of drug-likeness and optimal properties for anthelmintic agents.Item Novel Fluorescent Benzimidazole-Hydrazone-Loaded Micellar Carriers for Controlled Release: Impact on Cell Toxicity, Nuclear and Microtubule Alterations in Breast Cancer Cells(2023-06-01) Bryaskova R.; Georgiev N.; Philipova N.; Bakov V.; Anichina K.; Argirova M.; Apostolova S.; Georgieva I.; Tzoneva R.Fluorescent micellar carriers with controlled release of a novel anticancer drug were developed to enable intracellular imaging and cancer treatment simultaneously. The nanosized fluorescent micellar systems were embedded with a novel anticancer drug via the self-assembling behavior of well-defined block copolymers based on amphiphilic poly(acrylic acid)-block-poly(n-butyl acrylate) (PAA-b-PnBA) copolymer obtained by Atom Transfer Radical Polymerization (ATRP) and hydrophobic anticancer benzimidazole-hydrazone drug (BzH). Through this method, well-defined nanosized fluorescent micelles were obtained consisting of a hydrophilic PAA shell and a hydrophobic PnBA core embedded with the BzH drug due to the hydrophobic interactions, thus reaching very high encapsulation efficiency. The size, morphology, and fluorescent properties of blank and drug-loaded micelles were investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM), and fluorescent spectroscopy, respectively. Additionally, after 72 h of incubation, drug-loaded micelles released 3.25 μM of BzH, which was spectrophotometrically determined. The BzH drug-loaded micelles were found to exhibit enhanced antiproliferative and cytotoxic effects on MDA-MB-231 cells, with long-lasting effects on microtubule organization, with apoptotic alterations and preferential localization in the perinuclear space of cancer cells. In contrast, the antitumor effect of BzH alone or incorporated in micelles on non-cancerous cells MCF-10A was relatively weak.Item PORPHYRINE/SILVER NANOPARTICLES BASED PHOTOACTIVE ANTIBACTERIAL COATINGS(2023-01-01) Philipova N.; Georgiev N.; Ganchev D.; Lalov I.; Bryaskova R.A novel amino-modified protoporphyrin IX with included silver nanoparticles (PPIX-ED/AgNPs) complex was synthesized and used as a last layer for preparation of photoactive antibacterial coatings. The obtained PPIX-ED/ AgNPs complex was appropriately analyzed using various spectroscopic methods such as fluorescence analysis and infrared spectroscopy (ATR-FTIR). The size and morphology of the synthesized PPIX-ED/AgNPs complex were analyzed by Transmission electron microscopy (TEM) and dynamic light scattering (DLS). Then, the photoactive antibacterial coatings were obtained by deep coating procedure as the last layer consists of PPIX-ED/AgNPs complex, which is expected to possess strong antibacterial activity. The EDX-SEM analysis was employed to prove the deposition of the layers and nanoindentation analysis was used to determine their mechanical properties. The antibacterial properties of the photoactive coatings against G. negative E. coli and G. positive B. Subtilis were determined using disk diffusion method (DDM).Item Recent Advances in the Application of Nitro(het)aromatic Compounds for Treating and/or Fluorescent Imaging of Tumor Hypoxia(2024-08-01) Anichina K.; Lumov N.; Bakov V.; Yancheva D.; Georgiev N.This review delves into recent advancements in the field of nitro(het)aromatic bioreductive agents tailored for hypoxic environments. These compounds are designed to exploit the low-oxygen conditions typically found in solid tumors, making them promising candidates for targeted cancer therapies. Initially, this review focused on their role as gene-directed enzyme prodrugs, which are inert until activated by specific enzymes within tumor cells. Upon activation, these prodrugs undergo chemical transformations that convert them into potent cytotoxic agents, selectively targeting cancerous tissue while sparing healthy cells. Additionally, this review discusses recent developments in prodrug conjugates containing nitro(het)aromatic moieties, designed to activate under low-oxygen conditions within tumors. This approach enhances their efficacy and specificity in cancer treatment. Furthermore, this review covers innovative research on using nitro(het)aromatic compounds as fluorescent probes for imaging hypoxic tumors. These probes enable non-invasive visualization of low-oxygen regions within tumors, providing valuable insights for the diagnosis, treatment planning, and monitoring of therapeutic responses. We hope this review will inspire researchers to design and synthesize improved compounds for selective cancer treatment and early diagnostics.Item Self-Assembled Molecular Complexes of 1,10-Phenanthroline and 2-Aminobenzimidazoles: Synthesis, Structure Investigations, and Cytotoxic Properties(2024-02-01) Anichina K.; Kaloyanov N.; Zasheva D.; Rusew R.; Nikolova R.; Yancheva D.; Bakov V.; Georgiev N.Three new molecular complexes (phen)3(2-amino-Bz)2(H+)(BF4−)·3H2O 5, (phen)3(2-amino-5(6)-methyl-Bz)2(H+)(BF4−)·H2O 6, and (phen)(1-methyl-2-amino-Bz)(H+)(BF4−) 7, were prepared by self-assembly of 1,10-phenanthroline (phen) and various substituted 2-aminobenzimidazoles. Confirmation of their structures was established through spectroscopic methods and elemental analysis. The X-ray diffraction analysis revealed that the crystal structure of 7 is stabilized by the formation of hydrogen bonds and short contacts. In addition, the molecular geometry and electron structure of molecules 5 and 6 were theoretically evaluated using density functional theory (DFT) methods. According to the DFT B3LYP/6-311+G* calculations, the protonated benzimidazole (Bz) units act as NH hydrogen bond donors, binding two phenanthrolines and a BF4− ion. Non-protonated Bz unit form hydrogen bonds with the N-atoms of a third molecule phen. The molecular assembly is held together by π-π stacking between benzimidazole and phenanthroline rings, allowing for N-atoms to associate with water molecules. The complexes were tested in vitro for their tumor cell growth inhibitory effects on prostate (PC3), breast (MDA-MB-231 and MCF-7), and cervical (HeLa) cancer cell lines using MTT-dye reduction assay. The in vitro cytotoxicity analysis and spectrophotometric investigation in the presence of ct-DNA, showed that self-assembled molecules 5–7 are promising DNA-binding anticancer agents warranting further in-depth exploration.Item Sensor activity and logic behaviour of some 2-aminoterephthalic derivatives(2014-01-01) Miladinova P.; Georgiev N.Herein we report on the sensor activity of three blue-emitting triazine derivatives of 2-aminoterephthalic acid. The novelfompounds are conigured as a ``luorophore-receptor`` system. The luorophores designed can act as a pH-probe via an ``off-on-off`` luorescence sensing mechanism due to an internal charge transfer. The sensor activity towards cations and anions in water/DMF (1:1, v/v) media is studied by monitoring the luorescence intensity changes. The ions tested exert a high quenching effect suggesting that the compounds are sensitive to strong acid (pH<3) and strong alkaline media (pH>8). The logic function XNOR can be performed using an acid and a base as chemical inputs, while a digital comparator can be designed on the ground of pH induced changes in the spectral properties of the novel molecule.Item Synthesis, chemosensing properties and logic behaviour of a novel ratiometric 1,8-naphthalimide probe based on ICT and PET(2016-08-01) Georgiev N.; Dimitrova M.; Todorova Y.; Bojinov V.A novel fluorescence sensing 1,8-naphthalimide designed on the ``receptor1-fluorophore-spacer-receptor2`` model is synthesized and investigated. The novel probe comprising aminotriazole and hydroxyphenyl substituents is capable to operate simultaneously via ratiometric ICT and PET signalling mechanism. The synthesized compound shows excellent signalling properties towards protons, hydroxyl anions and Cu2+ ions. Due to the remarkable fluorescence changes in the presence of these analytes the system is able to act as a two output combinatorial logic circuit with three chemical inputs. Input3-Disabled XNOR, INHIBIT and IMPLICATION logic gates were obtained. Because of the parallel action of disabled-XNOR and disabled-INHIBIT gates a magnitude digital comparator with disable capability is achievable.