Structure and electrochemical properties of magnetite and polypyrrole nanocomposites formed by pyrrole oxidation with magnetite nanoparticles

Nanocomposite of magnetic Fe₃O₄ nanoparticles and polypyrrole was prepared under sonication by a new chemical polymerization method during which Fe₃O₄ nanoparticles acted both as a pyrrole oxidant and as a component in the composite material. Synthesis of this nanocomposite was carried out in aqueous solution acidified to pH 2, a prerequisite for the formation of these types of material and to facilitate pyrrole oxidation by Fe₃O₄ nanoparticles. In this way, two kind of materials were produced: Fe₃O₄/PPy nanocomposite in which magnetite nanoparticles were dispersed in PPy matrix and Fe₃O₄-aggregates@PPy nanocomposite that exhibits structure in which aggregates of magnetite nanoparticles are surrounded by a layer of polymeric phase. In the latter case, the polymerization process took place in the presence of a surfactant. These nanocomposites were characterized by electron microscopy techniques, IR spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and thermogravimetry. Particular attention was focused on the study of the electrochemical properties of the formed composites. The composite of Fe₃O₄ and PPy exhibits reversible electrochemical behaviour upon oxidation. The electrode process of the polymeric component oxidation in organic solvents such as acetonitrile and dichloromethane is very similar to the process in an aqueous solution.

     

Methionine Capped Nanoparticles as Acetylcholinesterase Inhibitors

The silver and gold L-methionine capped nanoparticles (Ag and Au @LM NPs) were analyzed as prospective acetylcholinesterase (AChE) inhibitors to test their potential in the treatment of cognitive impairment in depression and Alzheimer's disease. The stability of NPs, and their ability to inhibit AChE were studied by UV-Vis and FTIR spectrophotometry. At the same time, TEM and SEM measurements, DLS, and zeta potential measurements were employed in the structural characterization of NPs. Nearly spherical, negatively charged Ag and Au @LM NPs, with 17 nm and 31 nm in diameter, respectively, showed moderate inhibitory potential toward AChE in the given frame of investigated concentrations. For both NPs IC50 is not reached. Furthermore, the adsorption of enzyme molecules on the surface of Ag and Au @LM NPs was demonstrated. Hence, our assumption is that inhibition of AChE is caused by blockage of the enzyme‘s active site due to the steric hindrance of NPs.