α-synuclein interaction with zero-valent iron nanoparticles accelerates structural rearrangement into amyloid-susceptible structure with increased cytotoxic tendency.

AIM: It has been indicated that NPs may change the amyloidogenic steps of proteins and relevant cytotoxicity. Therefore, this report assigned to explore the impact of ZVFe NPs on the amyloidogenicity and cytotoxicity of α-synuclein as one of the many known amyloid proteins. METHODS: The characterization of α-synuclein at amyloidogenic condition either alone or with ZVFe NPs was carried out by fluorescence, CD, UV-visible spectroscopic methods, TEM study, docking, and molecular modeling. The cytotoxicity assay of α-synuclein amyloid in the absence and presence of ZVFe NPs was also done by MTT, LDH, and flow cytometry analysis. RESULTS: ThT fluorescence spectroscopy revealed that ZVFe NPs shorten the lag phase and accelerate the fibrillation rate of α-synuclein. Nile red and intrinsic fluorescence spectroscopy, CD, Congo red adsorption, and TEM studies indicated that ZVFe NP increased the propensity of α-synuclein into the amyloid fibrillation. Molecular docking study revealed that hydrophilic residues, such as Ser-9 and Lys-12 provide proper sites for hydrogen bonding and electrostatic interactions with adsorbed water molecules on ZVFe NPs, respectively. Molecular dynamics study determined that the interacted protein shifted from a natively discorded conformation toward a more packed structure. Cellular assay displayed that the cytotoxicity of α-synuclein amyloid against SH-SY5Y cells in the presence of ZVFe NPs is greater than the results obtained without ZVFe NPs. CONCLUSION: In conclusion, the existence of ZVFe NPs promotes α-synuclein fibrillation at amyloidogenic conditions by forming a potential template for nucleation, the growth of α-synuclein fibrillation and induced cytotoxicity.

The interaction of silica nanoparticles with catalase and human mesenchymal stem cells: biophysical, theoretical and cellular studies.

AIM: Nanoparticles (NPs) have been receiving potential interests in protein delivery and cell therapy. As a matter of fact, NPs may be used as great candidates in promoting cell therapy by catalase (CAT) delivery into high oxidative stress tissues. However, for using NPs like SiO2 as carriers, the interaction of NPs with proteins and mesenchymal stem cells (MSCs) should be explored in advance. METHODS: In the present study, the interaction of SiO2 NPs with CAT and human MSCs (hMSCs) was explored by various spectroscopic methods (fluorescence, circular dichroism (CD), UV-visible), molecular docking and dynamics studies, and cellular (MTT, cellular morphology, cellular uptake, lactate dehydrogenase, ROS, caspase-3, flow cytometry) assays. RESULTS: Fluorescence study displayed that both dynamic and static quenching mechanisms and hydrophobic interactions are involved in the spontaneous interaction of SiO2 NPs with CAT. CD spectra indicated that native structure of CAT remains stable after interaction with SiO2 NPs. UV-visible study also revealed that the kinetic parameters of CAT such as Km, Vmax, Kcat, and enzyme efficiency were not changed after the addition of SiO2 NPs. Molecular docking and dynamics studies showed that Si and SiO2 clusters interact with hydrophobic residues of CAT and SiO2 cluster causes minor changes in the CAT structure at a total simulation time of 200 ps. Cellular assays depicted that SiO2 NPs induce significant cell mortality, change in cellular morphology, cellular internalization, ROS elevation, and apoptosis in hMSCs at higher concentration than 100 µg/mL (170 µM). CONCLUSION: The current results suggest that low concentrations of SiO2 NPs induce no substantial change or mortality against CAT and hMSCs, and potentially useful carriers in CAT delivery to hMSC.