The effects of Fe2O3 nanoparticles on catalytic function of human acetylcholinesterase: size and concentration role

Iron oxide NPs (which consist of maghemite (γ-Fe2 O3 ) and/or magnetite (Fe3 O4 ) particles) are among the most important nanomaterials.5 Fe2 O3 NPs have gained considerable attention because of their unique intrinsic features, such as outstanding biocompatibility and superior magnetic properties.6,7 These NPs are widely used in a variety of fields, such as sensing technologies, memory storage devices, magnetic separation, magnetic labeling, catalytic processes, and biomedicine (heating for hyperthermia treatments, providing contrast effects for magnetic imaging, and remotely controlling the delivery of targeted drugs).8-10 NPs are small particles with large surface-to-volume ratios.11,12 It has been accepted that the small size of NPs can cause these materials to enter cells quickly, pass through the blood-brain barrier, and interact with different kinds of proteins and enzymes.13 In general, the conformation and function of enzymes and proteins are widely associated with their tertiary structure and protein dysfunction can lead to various diseases and disorders.14 Acetylcholinesterase (AChE), a critical serine hydrolase, is secreted into the synaptic space by postsynaptic cholinergic neurons.15 AChE is a crucial enzyme for the growth and operation of the central nervous system. The interaction between thiocholine and DTNB results in 5-thio-2-nitrobenzoate production.23,24 Circular dichroism spectroscopy To obtain insight into the potential effects of Fe2 O3 NPs on the secondary structure of AChE, the circular dichroism spectroscopy (CD) spectra of AChE in the absence or presence of Fe2 O3 NPs were measured in the far UV spectral region (200-250 nm) using a Jasco model spectropolarimeter at 25 °C. In this regard, different concentrations of Fe2 O3 NPs (0-1000 nM) were added to 1.0 mL of 20 mM phosphate buffer solution (pH 7.4; 310 K) containing 2.0 mg/mL AChE. [...]the immobilization process was completed by using 0.1 M ethanolamine-HCl (pH=8.5), which was injected into the Au chip surface to block the non-specific binding sites. SPR Navi™ data viewer software and Trace Drawer™ were utilized for data analysis and the calculation of the interaction parameters, respectively Fluorescence spectroscopy In this work, fluorescence spectroscopy was used to evaluate the conformational changes of AChE upon interaction with Fe2 O3 NPs.