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Graphical abstract Highlights • Sub-micellar TX-100 concentrations caused two dissimilar amyloid aggregation phases. • TX-100 induced the inhibition and the morphological phases were revealed. • Two stages of insulin thermal denaturation in the presence of TX-100 were observed. • TX-100 preferentially binds to two binding sites with different affinity. • Important is the protein:TX-100 ratio, not the total amount of TX-100. Abstract Atomic force microscopy, Thioflavin T (ThT) fluorescence assay, circular dichroism spectroscopy, differential scanning calorimetry, and molecular modeling techniques have been employed to investigate the amyloid aggregation of insulin in the presence of non-ionic detergent, Triton X-100 (TX-100). In contrast to recently described inhibition of lysozyme amyloid formation by non-ionic detergents (Siposova, 2017), the amyloid aggregation of insulin in the presence of sub-micellar TX-100 concentration exhibits two dissimilar phases. The first, inhibition phase, is observed at the protein to detergent molar ratio of 1:0.1 to 1:1. During this phase, the insulin amyloid fibril formation is inhibited by TX-100 up to ∼60%. The second, "morphological" phase, is observed at increasing detergent concentration, corresponding to protein:detergent molar ratio of ∼1:1 - 1:10. Under these conditions a significant increase of the steady-state ThT fluorescence intensities and a dramatically changed morphology of the insulin fibrils were observed. Increasing of the detergent concentration above the CMC led to complete inhibition of amyloidogenesis. Analysis of the experimental and molecular modeling results suggests an existence of up to six TX-100 binding sites within dimer of insulin with different binding energy. The physiological relevance of the results is discussed. [ABSTRACT FROM AUTHOR]

Two nonionic detergents, Triton X-100 (TX-100) and n -dodecyl-β- d -maltoside (DDM) were tested for their ability to affect lysozyme amyloid aggregation. We have demonstrated that fibrillization of lysozyme is completely inhibited by low sub-micellar concentrations of both of these detergents. The apparent IC 50 values were calculated to be 22 μM and 26 μM for TX-100 and DDM, respectively. The detergent/protein ratio is not the only parameter controlling inhibition. The precise timing of the detergent addition was found to be also crucial. It appears that the primary inhibitory activity of detergents resulted from inhibition of nuclei formation, in addition to inhibition of fibril polymerization at the early stage of protofibrils growth. The docking study revealed that Asn-59, Trp-63 and Ala-107, all present within the lysozyme amyloidogenic region, were involved in the interaction with both detergents. In addition, TX-100 also interacted with Gln-57 and Asp-103 within lysozyme. Moreover, based on our computational results, TX-100 bridges the Gln-57 and Ala-107 amino acids of the amyloidogenic segment of lysozyme and therefore inhibits more effectively the amyloid fibril formation. Along these lines, the knowledge gained from our study indicates that the detergents or their derivatives may be applicable as a promising strategy for the modulation of lysozyme protein aggregation. [ABSTRACT FROM AUTHOR]

• Amyloidogenesis of insulin is significantly affected by DDM in a time-and dose-dependent manner. • Amyloidogenesis of insulin only slightly affected by studied phospholipids (PLs). • DDM and the PLs occupy equivalent binding sites; however, the resulting effect on insulin aggregation is noticeably different. • Detergents and phospholipids are not always interchangeable in their use to investigate protein amyloid aggregation. • Hydrogen bonds indicated from MD simulations is the decisive factor for larger anti-aggregation effect of DDM over the PLs. Amphiphilic compounds, both detergents and lipids, are important tools for in vitro analysis of water-soluble and integral membrane proteins. A key question is whether these two groups of amphiphilic molecules use the same pathway to affect structural and functional integrity of proteins. In the present study, we tested the effect of non-ionic detergent dodecyl maltoside (DDM), two phospholipids, 1,2-dimyristoyl- sn -glycero-3- phosphocholine (DMPC), 1,2-dihexanoyl- sn -glycero-3-phosphocholine (DHPC), and the detergent-phospholipid mixtures on insulin amyloidogenesis in vitro. Amyloidogenesis of insulin is significantly affected by DDM in a time-and dose-dependent manner, but only slightly affected by either of phospholipids. Addition of DHPC or DMPC to detergent does not alter the inhibiting pattern, suggesting that DDM preferably binds to insulin. The molecular modeling revealed that DDM and the phospholipids occupy equivalent binding sites. DDM, due to the presence of maltose with several oxygen atoms (hydroxylic, glycosidic and ring) is involved in more hydrogen bonds than DHPC or DMPC. Hydrophobic interactions are important factors to stabilize both, DDM and phospholipids in their binding sites. Our results indicate that certain detergents (applying DDM as an example) and selected phospholipids are not always interchangeable in their use to investigate the effect of amphiphilic compounds on the behavior of amyloid-prone proteins. [ABSTRACT FROM AUTHOR]

An adsorption of magnetic nanoparticles (MNP) from electrostatically stabilized aqueous ferrofluids on amyloid fibrils of hen egg white lysozyme (HEWL) in 2 mg/mL acidic dispersions have been detected for the MNP concentration range of 0.01–0.1 vol.%. The association of the MNP with amyloid fibrils has been characterized by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and magneto-optical measurements. It has been observed that the extent of adsorption is determined by the MNP concentration. When increasing the MNP concentration the formed aggregates of magnetic particles repeat the general rod-like structure of the fibrils. The effect is not observed when MNP are mixed with the solution of lysozyme monomers. The adsorption has been investigated with the aim to clarify previously found disaggregation activity of MNP in amyloid fibrils dispersions and to get deeper insight into interaction processes between amyloids and MNP. The observed effect is also discussed with respect to potential applications for ordering lysozyme amyloid fibrils in a liquid crystal phase under external magnetic fields. [ABSTRACT FROM AUTHOR]

Cerium dioxide nanoparticles (CeO 2 NPs) are used increasingly in nanotechnology and particularly in biotechnology and bioresearch. Thus, CeO 2 NPs have been successfully tested in vitro as a potential therapeutic agent for various pathologies associated with oxidative stress, including the formation of protein amyloid aggregates. In this study, to increase the anti-amyloidogenic efficiency and preserve the antioxidant potential, the surface of the synthesized CeO 2 NPs is modified with a nonionic, sugar-based surfactant, dodecyl maltoside (DDM), which is known for its high anti-amyloidogenic activity and biocompatibility. Dynamic light scattering and Fourier transform infrared spectroscopy demonstrated successful modification by DDM. The apparent hydrodynamic diameters of CeO 2 NPs and DDM-modified NPs (CeO 2 @DDM NPs) are found to be ⁓180 nm and ⁓260 nm, respectively. A positive zeta potential value of + 30.5 mV for CeO 2 NPs and + 22.5 mV for CeO 2 @DDM NPs suggest sufficient stability and good dispersion of NPs in an aqueous solution. A combination of Thioflavin T fluorescence analysis and atomic force microscopy is used to assess the effect of nanoparticles on the formation of insulin amyloid fibrils. Results show that the fibrillization of insulin is inhibited by both, naked and modified NPs in a dose-dependent manner. However, while the IC 50 of naked NPs is found to be ∼270 ± 13 µg/mL, the surface-modified NPs are 50% more efficient with IC 50 equaled to 135 ± 7 µg/mL. In addition, both, the naked CeO 2 NPs and DDM-modified NPs displayed an antioxidant activity expressed as oxidase-, catalase- and SOD-like activity. Therefore, the resulting nanosized material is very well suited to prove or disprove the hypothesis that oxidative stress plays a role in the formation of amyloid fibrils. [Display omitted] • CeO 2 nanoparticles modified with a nonionic surfactant, dodecyl maltoside (DDM). • DDM-modified NPs exhibit more than 50% enhanced anti-amyloid activity. • DDM-modified NPs displayed preserved antioxidant activity. [ABSTRACT FROM AUTHOR]

Cerium oxide nanoparticles (CeO 2 NPs) are well known for their application in various fields of industry, as well as in biology and medicine. Knowledge of synthesis schemes, physicochemical and morphological features of nanoscale CeO 2 is important for assessing their antioxidant behavior and understanding the mechanism of oxidative stress and its consequences. The choice of the method of synthesis should be based on the possibility to choose the conditions and parameters for obtaining CeO 2 with controlled dimensions and a ratio of Се3+/Се4+ on their surface. In this study, CeO 2 NPs are synthesized by precipitation in mixed water-alcohol solutions at constant pH = 9. The properties of obtained NPs are studied using various methods of physical-chemical characterization such as X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. The size of CeO 2 NPs varied from 14 to 4.2 nm with increasing alcohol concentration, while the effect of constant pH during synthesis on the morphology of the particles was insignificant. The synthesized nanoparticles form highly stable aqueous suspensions since their zeta-potential is higher than + 40 mV. It is found that the ability of CeO 2 NPs to self-stabilize is associated with the presence of hydrated Ce4+ ions on their surface. In vitro biological studies have shown that, regardless of particle size, CeO 2 NPs have antioxidant potential, but smaller NPs with a higher percentage of Ce3+ on the surface had a more effective antioxidant effect. In addition, the size-depended activity of CeO 2 NPs to inhibit the amyloid formation of insulin is demonstrated. [Display omitted] • CeO 2 nanoparticles were synthesized at constant pH = 9. • Ce3+ percentage on the surface growth with the decreasing particles size. • Maintaining pH during the synthesis affects the particles size distribution. • CeO 2 nanoparticles are self-stabilized in the aqueous suspensions. • CeO 2 nanoparticles possess dual antioxidant and anti-amyloid activities. [ABSTRACT FROM AUTHOR]