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    Antibacterial potentials of carbon dots immobilized on chitosan and glass surfaces
    (Elsevier, 2024) Ghaibullah, Yanar Najmalden Ghaibullah; Foto, Egemen; Ozdemir, Naciye; Foto, Fatma Zilifdar; Arslan, Gulsin; Sargin, Idris
    Due to their antibacterial activity, chitosan-carbon dot composites possess great potential for pharmaceuticals, medicine, and food preservation. Conducting a comprehensive study of the interactions between chitosan, carbon dots, and bacteria is crucial to understanding the processes behind applying these composites. This study aimed to immobilize carbon dots (C-dots) synthesized from Elaeagnus angustifolia fruits on chitosan and glass microbeads' surfaces, to characterize the test materials obtained after synthesis and immobilization, and to investigate their antibacterial potentials.C-dot synthesis was carried out from water extract in an acidic medium with the help of microwave irradiation, and their structural and optical properties were characterized by TEM, XRD, FT-IR, UV-vis, Zeta potential, and fluorescence methods. The surface of the glass microbeads was first activated and functionalized with surface amine groups with a silaning agent. C-dots were immobilized on both glass and chitosan microbeads using a crosslinking agent. Antibacterial potentials of nine different test materials, obtained before or after immobilization, were evaluated both qualitatively (MIC and MBC) and quantitatively (GI50) on E. coli, S. typhimurium, B. subtilis, and S. aureus, with the standard broth microdilution method.FT-IR and SEM-EDX analyses showed that C-dots were immobilized on chitosan (<1 mm) and glass (<100 mu m) microbead surfaces. C-dots reduced the cell viability by similar to 25 % on S. typhimurium and B. subtilis (MIC = 25 mg/ mL). It was also found that the highest antibacterial effect was recorded for C-dots-glass microbeads, which had a toxic effect of 43 % on S. aureus. In addition, binding C-dots to glass microbeads increased the antibacterial effect selectively in Gram-positive bacteria, while binding to chitosan microbeads was effective in all bacteria. The study showed that the antibacterial potential of C-dots-chitosan microbeads is more effective than C-dots-glass microbeads. C-dots could be used as carbon-based nanomaterials in antibacterial surface preparation once immobilized.
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    Antioxidative and antiproliferative effects of propolis-reduced silver nanoparticles
    (Techno-Press, 2021) Tan, Gamze; Ilk, Sedef; Foto, Fatma Z.; Foto, Egemen; Saglam, Necdet
    In this study, phytochemicals present in Propolis Extract (PE) were employed as reducing and stabilizing reagents to synthesize silver nanoparticles. Three propolis-reduced silver nanoparticles (P-AgNPs1-3) were synthesized using increasing amounts of PE. P-AgNPs were treated with different cancer cells -lung (A549), cervix (HeLa) and colon (WiDr) for 24, 48 and 72 h to evaluate their anti -proliferative activities. A non-cancerous cell type (L929) was also used to test whether suppressive effects of P-AgNPs on cancer cell proliferation were due to a general cytotoxic effect. The characterization results showed that the bioactive contents in propolis successfully induced particle formation. As the amount of PE increased, the particle size decreased; however, the size distribution range expanded. The antioxidant capacity of the particles increased with increased propolis amounts. P-AgNP1 exhibited almost equal inhibitory effects across all cancer cell types; however, P-AgNP2 was more effective on HeLa cells. P-AgNPs3 showed greater inhibitory effects in almost all cancer cells compared to other NPs and pure propolis. Consequently, the biological effects of P-AgNPs were highly dependent on PE amount, NP concentration, and cell type. These results suggest that AgNPs synthesized utilizing propolis phytochemicals might serve as anti -cancer agents, providing greater efficacy against cancer cells.
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    Antioxidative and antiproliferative effects of propolis-reduced silver nanoparticles
    (Techno-Press, 2021) Tan, Gamze; Ilk, Sedef; Foto, Fatma Z.; Foto, Egemen; Saglam, Necdet
    In this study, phytochemicals present in Propolis Extract (PE) were employed as reducing and stabilizing reagents to synthesize silver nanoparticles. Three propolis-reduced silver nanoparticles (P-AgNPs1-3) were synthesized using increasing amounts of PE. P-AgNPs were treated with different cancer cells -lung (A549), cervix (HeLa) and colon (WiDr) for 24, 48 and 72 h to evaluate their anti -proliferative activities. A non-cancerous cell type (L929) was also used to test whether suppressive effects of P-AgNPs on cancer cell proliferation were due to a general cytotoxic effect. The characterization results showed that the bioactive contents in propolis successfully induced particle formation. As the amount of PE increased, the particle size decreased; however, the size distribution range expanded. The antioxidant capacity of the particles increased with increased propolis amounts. P-AgNP1 exhibited almost equal inhibitory effects across all cancer cell types; however, P-AgNP2 was more effective on HeLa cells. P-AgNPs3 showed greater inhibitory effects in almost all cancer cells compared to other NPs and pure propolis. Consequently, the biological effects of P-AgNPs were highly dependent on PE amount, NP concentration, and cell type. These results suggest that AgNPs synthesized utilizing propolis phytochemicals might serve as anti -cancer agents, providing greater efficacy against cancer cells.
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    Benzoxazines as new human topoisomerase I inhibitors and potential poisons
    (Springer International Publishing Ag, 2020) Foto, Egemen; Ozen, Cigdem; Zilifdar, Fatma; Tekiner-Gulbas, Betul; Yildiz, Ilkay; Aki-Yalcin, Esin; Diril, Nuran
    Background The numbers of topoisomerase I targeted drugs on the market are very limited although they are used clinically for treatment of solid tumors. Hence, studies about finding new chemical structures which specifically target topoisomerase I are still remarkable. Objectives In this present study, we tested previously synthesized 3,4-dihydro-2H-1,4-benzoxazin-3-one derivatives to reveal their human DNA topoisomerase I inhibitory potentials. Methods We investigated inhibitory activities of 3,4-dihydro-2H-1,4-benzoxazin-3-one derivatives on human topoisomerase I by relaxation assay to clarify inhibition mechanisms of effective derivatives with EMSA and T4 DNA ligase based intercalation assay. With SAR study, it was tried to find out effective groups in the ring system. Results While 10 compounds showed catalytic inhibitory activity, 8 compounds were found to be potential topoisomerase poisons. 4 of them also exhibited both activities. 2-hydroxy-3,4-dihydro-2H-1,4-benzoxazin-3-one (BONC-001) was the most effective catalytic inhibitor (IC50:8.34 mM) and ethyl 6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-acetate (BONC-013) was the strongest potential poison (IC50:0.0006 mM). BONC-013 was much more poisonous than camptothecin (IC50:0.034 mM). Intercalation assay showed that BONC-013 was not an intercalator and BONC-001 most probably prevented enzyme-substrate binding in an unknown way. Another important result of this study was that OH group instead of ethoxycarbonylmethyl group at R position of benzoxazine ring was important for hTopo I catalytic inhibition while the attachment of a methyl group of R1 position at R-2 position were play a role for increasing of its poisonous effect. Conclusion As a result, we presented new DNA topoisomerase I inhibitors which might serve novel constructs for future anticancer agent designs. Graphical abstract
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    Biological activity and ADME/Tox prediction of some 2-substituted benzoxazole derivatives
    (Academic Press Inc Elsevier Science, 2022) Foto, Fatma Zilifdar; Foto, Egemen; Ertan-Bolelli, Tugba; Yildiz, Ilkay
    In this study, we mainly focused on some in vitro biological activities of a series of (5 or 6)-amino-2- (substituted phenyl and benzyl) benzoxazole derivatives. For this purpose, we tested cytotoxic and genotoxic activities of them on cancer cell lines and their topoisomerase inhibitory activities. We also tested their cytotoxic and genotoxic activities on non-cancerous cells (L929) and their mutagenic activities by Ames test to evaluate their effects on healthy cells. Only TD5 was found cytotoxic on all the tested cancer cell lines and did not exhibit either cytotoxic or genotoxic activities against healthy cells, whereas TD1, TD2, TD3 and TD7 were more cytotoxic against only HeLa cells. Only TD4 was found as mutagenic derivative. None of the compounds had any topoisomerase inhibitory activities nevertheless some of them caused inhibition of topoisomerase II activity. Additionally, we used an in silico model to predict the drug-like properties of them to evaluate their bioavailability to the QikProp Properties Predictions. All the calculated properties were found in a permissible range. According to the data obtained from biological activity studies, it can be concluded that the methylene bridge at the position 2 of benzoxazole ring decreases cytotoxic activity on cancer cells and inhibitory activity on DNA topoisomerases.
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    Discovery of 5-(or 6)-benzoxazoles and oxazolo[4,5-b]pyridines as novel candidate antitumor agents targeting hTopo II?
    (Academic Press Inc Elsevier Science, 2021) Karatas, Esin; Foto, Egemen; Ertan-Bolelli, Tugba; Yalcin-Ozkat, Gozde; Yilmaz, Serap; Ataei, Sanaz; Zilifdar, Fatma
    Discovery of novel anticancer drugs which have low toxicity and high activity is very significant area in anticancer drug research and development. One of the important targets for cancer treatment research is topoisomerase enzymes. In order to make a contribution to this field, we have designed and synthesized some 5(or 6)-nitro-2-(substitutedphenyl)benzoxazole (1a-1r) and 2-(substitutedphenyl)oxazolo[4,5-b]pyridine (2a-2i) derivatives as novel candidate antitumor agents targeting human DNA topoisomerase enzymes (hTopo I and hTopo II alpha). Biological activity results were found very promising for the future due to two compounds, 5-nitro-2-(4butylphenyl)benzoxazole (1i) and 2-(4-butylphenyl)oxazolo[4,5-b]pyridine (2i), that inhibited hTopo II alpha with 2 mu M IC50 value. These two compounds were also found to be more active than reference drug etoposide. However, 1i and 2i did not show any satisfactory cyctotoxic activity on the HeLa, WiDR, A549, and MCF7 cancer cell lines. Moreover, molecular docking and molecular dynamic simulations studies for the most active compounds were applied in order to understand the mechanism of inhibition activity of hTopo II alpha. In addition, in silico ADME/Tox studies were performed to predict drug-likeness and pharmacokinetic properties of all the tested compounds.
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    Evaluation of Mutagenic Activities of Antimicrobial Benzoxazole Derivatives
    (Springer, 2022) Aydogan, Zeliha; Foto, Fatma Zilifdar; Foto, Egemen; Temiz-Arpaci, Ozlem; Diril, Nuran
    Benzoxazoles are heterocyclic compounds containing fused benzene and oxazole rings, which have been reported to possess antibacterial, antitubercular, antifungal, antiviral, antioxidant and anticancer activities. In this study, the mutagenic properties of fifteen benzoxazole derivatives reported previously to exhibit broad antimicrobial and potent antitumor effects were investigated for their genotoxic potential by employing the Ames test. The Ames test was conducted using Salmonella typhimurium TA98, TA100 and TA102 tester strains in the standard plate incorporation assay with and without liver S9 fraction. The results were evaluated statistically and no mutagenic activity of test drugs was observed. Relationship between the structure and cytotoxic activity of compounds was evaluated using the SAR method based on data obtained via the Ames test system.