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    Quercetin- and caffeic acid-functionalized chitosan-capped colloidal silver nanoparticles: one-pot synthesis, characterization, and anticancer and antibacterial activities
    (Beilstein-Institut, 2023) Kurt, Akif Hakan; Olutas, Elif Berna; Avcioglu, Fatma; Karakus, Hamza; Sungur, Mehmet Ali; Oztabag, Cansu Kara; Yildirim, Muhammet
    The presented study comprises the one-pot synthesis and the characterization of quercetin-and caffeic acid-functionalized chitosan-capped colloidal silver nanoparticles (Ch/Q-and Ch/CA-Ag NPs), and their antibacterial and anticancer activities. The formation of Ch/Q-and Ch/CA-Ag NPs has been confirmed by ultraviolet-visible (UV-vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The characteristic surface plasmon resonance (SPR) absorption band has been found at 417 and 424 nm for Ch/Q-and Ch/CA-Ag NPs, respectively. The formation of a chitosan shell comprising quercetin and caffeic acid, which surround the colloidal core Ag NPs, was confirmed by UV-vis, and FTIR analyses, and moni-tored by TEM microscopy. The size of nanoparticles has been determined as 11.2 and 10.3 nm for Ch/Q-and Ch/CA-Ag, respec-tively. The anticancer activity of Ch/Q-and Ch/CA-Ag NPs has been evaluated against U-118 MG (human glioblastoma) and ARPE-19 (human retinal pigment epithelium) cells. Both NPs showed anticancer activity, but Ch/Q-Ag NPs seemed to be more effective on cancer cell lines (U-118 MG) in comparison to healthy ones (ARPE-19). Furthermore, the antibacterial activity of Ch/Q-and Ch/CA-Ag NPs against Gram-negative (P. aeruginosa and E. coli) and Gram-positive (S. aureus and S. epidermidis) bacteria was determined, and dose-dependent antibacterial effects were found.
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    The Role of Estrogen Receptors in the Therapeutic Effect of Oxyresveratrol, Phytoestrogen, During, and After Oxidative Stress
    (Pleiades Publishing Ltd, 2024) Oztabag, Cansu Kara; Kurt, Akif Hakan; Ayaz, Lokman; Sungur, Mehmet Ali
    Objective: Oxidative stress plays a significant role in the development and progression of various neurodegenerative disorders, including aging, atherosclerosis, cancer, ischemia reperfusion, inflammation, rheumatoid arthritis, liver diseases. Additionally, it is implicated in retinal diseases (RD) such as glaucoma, diabetic retinopathy (DR), retinal vein occlusion (RVO), and age-related macular degeneration (AMD). In our study, we studied the therapeutic effect of oxyresveratrol, against H2O2-induced oxidative damage. Additionally, we investigated the role of estrogen receptors in the observed effects. Methods: Oxidative stress was induced by H2O2 in ARPE-19 cells. Oxyresveratrol was applied at seven different concentrations during and after oxidative stress. Besides, estrogen receptor inhibitors were applied 1 h before the treatment to investigate the role of estrogen receptors. Changes in cell viability were assessed using XTT. To investigate the effectiveness of oxyresveratrol at the molecular level, cell death detection, Caspase-3, and TOS measurement kits were employed. Results and Discussion: Our findings indicated that oxyresveratrol at concentrations of 10 and 100 mu M reduced cell damage in ARPE-19 cells during and after-induced oxidative stress. Additionally, the therapeutic effect of oxyresveratrol in ARPE-19 cells during oxidative stress formation appeared to be dependent on estrogen receptors alpha and beta, while the therapeutic effect after oxidative stress seemed to be GPER1-dependent. Furthermore, oxyresveratrol suppressed apoptosis in ARPE-19 cells under oxidative stress, reducing cell death, and both during and after oxidative stress, oxyresveratrol application decreased TOS levels. Although the antioxidant, anti-inflammatory, and neuroprotective effects of oxyresveratrol are well known, this is the first study to investigate its therapeutic effects on H2O2 induced oxidative stress in ARPE-19 cells and the involvement of estrogen receptors in these effects. Conclusions: We believe that oxyresveratrol may be an alternative therapy in the prevention and treatment of retinal diseases.