The authors demonstrate the exploitation of reduced graphene oxide (RGO) as a template for immobilizing zeolitic imidazolate framework-8 (ZIF-8) crystals loaded with the electrochemical probe Methylene Blue (MB). The framework was deposited on the surface of RGO in a one-pot process. Transmission electron microscopy, scanning electron microscopy and X-ray diffraction were employed to characterize the nanocomposite. The electrochemical behavior of rutin at a glassy carbon electrode (GCE) modified with the nanocomposite was investigated by cyclic voltammetry and differential pulse voltammetry. The modified GCE displays high electrocatalytic activity toward rutin oxidation at a relatively low working potential (0.4 V vs. Ag/AgCl). Under the optimal conditions, the sensor has an amperometric response that is linear in the 0.1 to 100 μM rutin concentration range, with a 20 nM detection limit (at an S/N ratio of 3). The method was successfully applied to the determination of rutin in tablets and urine samples. Graphical abstract The zeolitic imidazolate framework ZIF-8 was loaded with Methylene Blue and deposited on the surface of reduced graphene oxide. A glassy carbon electrode was modified with the nanocomposite and then used for the determination of rutin with a 20 nM detection limit and a linear range from 0.1 to 100 μM.
Extensive studies have reported that interaction of α-synuclein amyloid species with neurons is a crucial mechanistic characteristic of Parkinson’s disease (PD) and small molecules can downregulate the neurotoxic effects induced by protein aggregation. However, the exact mechanism(s) of these neuroprotective effects by small molecules remain widely unknown. In the present study, α-synuclein samples in the amyloidogenic condition were aged for 120 h with or without different concentrations of mitoquinone (MitoQ) as a quinone derivative compound and the amyloid characteristics and the relevant neurotoxicity were evaluated by Thioflavin T (ThT)/Nile red fluorescence, Congo red absorption, circular dichroism (CD), transmission electron microscopy (TEM), cell viability, lactate dehydrogenase (LDH), reactive oxygen species (ROS), reactive nitrogen species (RNS), malondialdehyde (MDA), superoxide dismutase (SOD), and caspase-9/-3 activity assays. Results clearly showed the capacity of MitoQ on the inhibition of the formation of α-synuclein fibrillation products through modulation of the aggregation pathway by an effect on the kinetic parameters. Also, it was shown that α-synuclein samples aged for 120 h with MitoQ trigger less neurotoxic effects against SH-SY5Y cells than α-synuclein amyloid alone. Indeed, co-incubation of α-synuclein with MitoQ reduced the membrane leakage, oxidative and nitro-oxidative stress, modifications of macromolecules, and apoptosis.
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