scholarly journals Evaluating Effect of Metallic Ions on Aggregation Behavior of Amyloid Aβ42 by AFM Imaging and SERS

2021 ◽  
Author(s):  
Yang Xie ◽  
Lin Yu ◽  
Yuna Fu ◽  
Heng Sun ◽  
Chundong Liu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Metal Cations ◽  
Aggregation Behavior ◽  
Metallic Ions ◽  
Gold Substrate ◽  
Self Assembled Monolayer ◽  
Afm Imaging ◽  
Surface Enhanced Raman ◽  
Aggregation Behaviors

Abstract In this study, self-assembled monolayer (SAM) method was employed to fabricate monolayer of β-amyloid peptides Aβ42 on gold substrate with a bolaamphiphile named thiol (MHA). Firstly, the samples of gold substrate (blank control), the MHA-modified substrate and the Aβ42-modified substrate were detected by X-ray photoelectron spectroscopy (XPS) to track the self-assembly process. The spectra of binding energy measured from these three sample surfaces could be well fitted with the corresponding monolayer’s composition, which means Aβ42 monolayer is well formed. Aggregation behaviors of Aβ42 in the absence and presence of metallic ions (Zn2+、Ca2+、Al3+) were then monitored by atomic force microscopy (AFM) and surface-enhanced Raman Scattering (SERS), respectively. The recorded surface morphology of different experimental groups obtained by AFM showed markedly different nanostructures, indicating occurrence of aggregation behaviors of Aβ42. In solutions with added metal ions, the increased size of surface structures was observed, which suggest the presence of metal cations promotes aggregation behavior between Aβ42 molecules. Furtherly, the interaction between Aβ42 and metal cations was investigated by SERS. The results demonstrate that the Raman strength of Aβ42 changes after the metal cation treatment. Taken together, the combined AFM imaging and Raman analyses show that the three kinds of metallic ions promote the process of Aβ42 aggregation.

scholarly journals Evaluating effect of metallic ions on aggregation behavior of β-amyloid peptides by atomic force microscope and surface-enhanced Raman Scattering

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Yang Xie ◽  
Lin Yu ◽  
Yuna Fu ◽  
Heng Sun ◽  
Jianhua Wang
Keyword(s):  
Metal Cations ◽  
Aggregation Behavior ◽  
Metallic Ions ◽  
Gold Substrate ◽  
Amyloid Peptides ◽  
Atomic Force ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Β Amyloid

Abstract Background Excessive aggregation of β-amyloid peptides (Aβ) is regarded as the hallmark of Alzheimer’s disease. Exploring the underlying mechanism regulating Aβ aggregation remains challenging and investigating aggregation events of Aβ in the presence and absence of metallic ions at molecular level would be meaningful in elucidating the role of metal cations on interactions between Aβ molecules. In this study, chemical self-assembled monolayer (SAM) method was employed to fabricate monolayer of β-amyloid peptides Aβ42 on gold substrate with a bolaamphiphile named 16-Mercaptohexadecanoic acid (MHA). Firstly, the samples of gold substrate (blank control), the MHA-modified substrate, and the Aβ42-modified substrate were detected by X-ray photoelectron spectroscopy (XPS) to track the self-assembly process. Aggregation behaviors of Aβ42 before and after metallic ions (Zn2+, Ca2+, Al3+) treatment were monitored by atomic force microscopy (AFM) and the interaction between Aβ42 and metallic ions (Zn2+, Ca2+, Al3+) was investigated by surface-enhanced Raman Scattering (SERS). Results The XPS spectra of binding energy of gold substrate (blank control), the MHA-modified substrate, and the Aβ42-modified substrate are well fitted with the corresponding monolayer’s composition, which indicates that Aβ42 monolayer is well formed. The recorded surface morphology of different experimental groups obtained by AFM showed markedly different nanostructures, indicating occurrence of aggregation events between Aβ42 molecules after adding metal ions to the solution. Compared to the control group, the presence of metallic ions resulted in the increased size of surface structures on the observed 3D topography. Besides, the intermolecular rupture force of Aβ42 increased with the addition of metallic ions. Further study by SERS showed that the Raman strength of Aβ42 changes significantly after the metal cation treatment. A considerable part of the amide bonds interacts with metal cations, leading to a structural change, which is characterized by the weakened β-fold Raman peak. Conclusion The AFM imaging results suggest that aggregation events occurred between Aβ42 molecules with the addition of metal cations. In addition, the results of force tests indicate that the presence of metallic ions could promote adhesion between Aβ42 molecules, which is likely to be the trigger for aggregation behavior of Aβ42. Furthermore, the effect of metallic cations on the conformational change of Aβ42 studied by SERS supported the results obtained by AFM. Taken together, the results showed that the presence of substoichiometric metal cations promotes aggregation behavior between Aβ42 molecules on the substrate at pH 7.4.

scholarly journals Evaluating Effect of Metallic Ions On Aggregation Behavior of Amyloid Aβ42 By AFM Imaging and SERS

2021 ◽  
Author(s):  
Yang Xie ◽  
Lin Yu ◽  
Yuna Fu ◽  
Heng Sun ◽  
Jianhua Wang
Keyword(s):  
Metal Ions ◽  
Metal Cations ◽  
Aggregation Behavior ◽  
Metallic Ions ◽  
Gold Substrate ◽  
Xps Spectra ◽  
Amyloid Peptides ◽  
Imaging Results ◽  
Afm Imaging ◽  
Β Amyloid

Abstract Background: Excessive aggregation of β-amyloid peptides (Aβ) is regarded as the hallmark of Alzheimer’s disease. Exploring the underlying mechanism regulating Aβ aggregation remains challenging and investigating aggregation events of Aβ in the presence and absence of metal ions at molecular level would be meaningful in elucidating the role of metal cations on interactions between Aβ molecules. In this study, chemical self-assembled monolayer (SAM) method was employed to fabricate monolayer of β-amyloid peptides Aβ42 on gold substrate with a bolaamphiphile named 16-Mercaptohexadecanoic acid (MHA). Firstly, the samples of gold substrate (blank control), the MHA-modified substrate and the Aβ42-modified substrate were detected by X-ray photoelectron spectroscopy (XPS) to track the self-assembly process. Aggregation behaviors of Aβ42 before and after metallic ions (Zn2+、Ca2+、Al3+) treated were monitored by atomic force microscopy (AFM) and the interaction between Aβ42 and metallic ions (Zn2+、Ca2+、Al3+) was investigated by surface-enhanced Raman Scattering (SERS), respectively.Results: The XPS spectra of binding energy of gold substrate (blank control), the MHA-modified substrate and the Aβ42-modified substrate are well fitted with the corresponding monolayer’s composition, which indicates that Aβ42 monolayer is well formed. The recorded surface morphology of different experimental groups obtained by AFM showed markedly different nanostructures, indicating occurrence of aggregation events between Aβ42 molecules after adding metal ions to the solution. Compared to the control group, the presence of metal ions resulted in the increased size of surface structures on the observed 3D topography. Further study by SERS showed that the Raman strength of Aβ42 changes significantly after the metal cation treatment. A considerable part of the amide bonds interacts with metal cations, leading to a structural change, which is characterized by the weakened β-fold Raman peak.Conclusion: The AFM imaging results suggest that aggregation events occurred between Aβ42 molecules with the addition of metal cations. Furthermore, the effect of metallic cations on the conformational change of Aβ42 studied by SERS supported the results obtained by AFM imaging. Taken together, the results showed that the presence of substoichiometric metal cations promotes aggregation behavior between Aβ42 molecules on the substrate at pH 7.4.

The Effects of the Self-Assembly Time on the Preparation of Lanthanum-Based Thin Films on Sulfonated 3-Mercaptopropyl Trimethoxysilane

2012 ◽  
Vol 164 ◽  
pp. 284-288
Author(s):  
Tao Bai ◽  
Xian Hua Cheng
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Self Assembled Monolayer ◽  
X Ray ◽  
Assembly Time ◽  
Force Microscopy ◽  
Angle Measurements ◽  
Atomic Force ◽  
Contact Angle Measurements

Lanthanum-based thin films are deposited on the oxidized 3-mercaptopropyl trimethoxysilane self-assembled monolayer (MPTS-SAM) based on the chemisorption of the sulfonic group. The surface energy, chemical composition, phase transformation and surface morphology of the films are analyzed by using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The experimental results indicate that the lanthanum-based thin films are absorbed on oxidized MPTS-SAM and lanthanum element with different oxidation states exists in the thin films deposited on the surface of self-assembly monolayers. The content of lanthanum on the oxidized MPTS-SAM increases with the extension of the assembly time and the rare earth reached saturation when the time was 6h.

DEEP UV PHOTOPATTERNING OF SELF-ASSEMBLED MONOLAYER AND ITS APPLICATION IN BIOELECTRONIC DEVICE

2002 ◽  
Vol 01 (05n06) ◽  
pp. 611-616 ◽  
Author(s):  
SE YOUNG OH ◽  
HANG SOK JIE ◽  
HYUNG SEOK CHOI ◽  
JEONG WOO CHOI
Keyword(s):  
Cytochrome C ◽  
Self Assembly ◽  
Fluorescent Protein ◽  
Uv Light ◽  
Scanning Tunneling ◽  
Gold Substrate ◽  
Self Assembled Monolayer ◽  
Patterned Substrate ◽  
Deep Uv ◽  
Self Assembled

The photopatterning process of self-assembled monolayer has been used as template for fabricating biomolecular microstructures. Alkanethiolates formed by the adsorption of 1-octanethiol molecules on a gold substrate were oxidized by the irradiation of deep UV light and then developed with deionized water. The resulting positive patterned substrate was immersed into a dilute ethanolic solution of 11-mercaptoundecanoic acid (11-MUDA). Cytochrome c monolayers were immobilized onto the patterned gold substrate by self-assembly technique and their electrochemical properties were investigated through the measurements of cyclic voltammetry. Also, I–V characteristics of biomolecular multilayers consisting of cytochrome c and green fluorescent protein (GFP) were studied with a scanning tunneling microscope (STM).

Controlled Interphase in Carbon Fiber/Epoxy Composites by Molecular Self-Assembly Method

2006 ◽  
Vol 313 ◽  
pp. 121-128
Author(s):  
J.M. He ◽  
Yu Dong Huang
Keyword(s):  
Carbon Fiber ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Epoxy Matrix ◽  
Fiber Surface ◽  
Assembly Method ◽  
Aromatic Thiols ◽  
Surface Enhanced Raman ◽  
Strong Adhesion ◽  
Carbon Fiber Surface

In this paper, a new method based on molecular self-assembly on carbon fiber surface was proposed for the improvement of interfacial properties between fiber and epoxy matrix in a composite system. In order to obtain the controlled interphase, the surface of carbon fibers was first metallized by electroless Ag plating, then was reacted with terminally functionized alkanethiols or aromatic thiols to form Ag-thiolate thin films, which further reacted with epoxy resin to generate a strong adhesion interface. The composition, structure and the morphology of the modified carbon fiber surface were examined by X-ray photoelectron spectroscopy (XPS), surface-enhanced Raman scattering (SERS) and atomic force microscope (AFM), respectively. The results showed that these self-assembly molecules were chemisorbed onto the carbon fiber surface coated with silver via the strong S-Ag bond. In addition, these thiol molecules act as coupling agents between the epoxy matrix and carbon fiber through active functional end-groups, such as –OH, -NH2. The interfacial shear strength (IFSS) of the microcomposites after introduced the controlled interphase using the microbond testing was improved.

scholarly journals Preparation of Fe3O4-Ag Nanocomposites with Silver Petals for SERS Application

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1288
Author(s):  
Thi Thuy Nguyen ◽  
Fayna Mammeri ◽  
Souad Ammar ◽  
Thi Bich Ngoc Nguyen ◽  
Trong Nghia Nguyen ◽  
...  
Keyword(s):  
Self Assembly ◽  
Hot Spots ◽  
Surface Enhanced Raman Spectroscopy ◽  
Electrical Field ◽  
Stabilizing Agents ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Sers Sensing ◽  
Applied Electrical Field ◽  
Positively Charged

The formation of silver nanopetal-Fe3O4 poly-nanocrystals assemblies and the use of the resulting hetero-nanostructures as active substrates for Surface Enhanced Raman Spectroscopy (SERS) application are here reported. In practice, about 180 nm sized polyol-made Fe3O4 spheres, constituted by 10 nm sized crystals, were functionalized by (3-aminopropyl)triethoxysilane (APTES) to become positively charged, which can then electrostatically interact with negatively charged silver seeds. Silver petals were formed by seed-mediated growth in presence of Ag+ cations and self-assembly, using L-ascorbic acid (L-AA) and polyvinyl pyrrolidone (PVP) as mid-reducing and stabilizing agents, respectively. The resulting plasmonic structure provides a rough surface with plenty of hot spots able to locally enhance significantly any applied electrical field. Additionally, they exhibited a high enough saturation magnetization with Ms = 9.7 emu g−1 to be reversibly collected by an external magnetic field, which shortened the detection time. The plasmonic property makes the engineered Fe3O4-Ag architectures particularly valuable for magnetically assisted ultra-sensitive SERS sensing. This was unambiguously established through the successful detection, in water, of traces, (down to 10−10 M) of Rhodamine 6G (R6G), at room temperature.

scholarly journals Improvement of the thermal stability of dendritic silver-coated copper microparticles by surface modification based on molecular self-assembly

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Tae Hyeong Kim ◽  
Hyeji Kim ◽  
Hyo Jun Jang ◽  
Nara Lee ◽  
Kwang Hyun Nam ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Electrically Conductive ◽  
X Ray ◽  
Alkyl Chains ◽  
Conductive Film ◽  
Initial Resistance ◽  
Thermal Stability Of ◽  
Scanning Electron

AbstractIn the study reported herein, silver-coated copper (Ag/Cu) powder was modified with alkanethiols featuring alkyl chains of different lengths, namely butyl, octyl, and dodecyl, to improve its thermal stability. The modification of the Ag/Cu powders with adsorbed alkanethiols was confirmed by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Each powder was combined with an epoxy resin to prepare an electrically conductive film. The results confirmed that the thermal stability of the films containing alkanethiol-modified Ag/Cu powders is superior to that of the film containing untreated Ag/Cu powder. The longer the alkyl group in the alkanethiol-modified Ag/Cu powder, the higher the initial resistance of the corresponding electrically conductive film and the lower the increase in resistance induced by heat treatment.

scholarly journals Microstructure and Properties of Self-Assembly Graphene Microcapsules: Effect of the pH Value

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 587 ◽  
Author(s):  
Yan-Dong Guo ◽  
Jun-Feng Su ◽  
Ru Mu ◽  
Xin-Yu Wang ◽  
Xiao-Long Zhang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Chemical Engineering ◽  
Ph Value ◽  
Liquid Paraffin ◽  
Energy Dispersive Spectrometer ◽  
Core Material ◽  
Microstructure And Properties ◽  
Ph Values

Graphene has attracted attention in the material field of functional microcapsules because of its excellent characteristics. The content and state of graphene in shells are critical for the properties of microcapsules, which are greatly affected by the charge adsorption equilibrium. The aim of this work was to investigate the effect of pH value on the microstructure and properties of self-assembly graphene microcapsules in regard to chemical engineering. Microcapsule samples were prepared containing liquid paraffin by a self-assembly polymerization method with graphene/organic hybrid shells. The morphology, average size and shell thickness parameters were investigated for five microcapsule samples fabricated under pH values of 3, 4, 5, 6 and 7. The existence and state of graphene in dry microcapsule samples were analyzed by using methods of scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Fourier Transform Infrared Spectoscopy (FT-IR) and Energy Dispersive Spectrometer (EDS) were applied to analyze the graphene content in shells. These results proved that graphene had existed in shells and the pH values greatly influenced the graphene deposition on shells. It was found that the microcapsule sample fabricated under pH = 5 experienced the largest graphene deposited on shells with the help of macromolecules entanglement and electrostatic adherence. This microcapsules sample had enhanced thermal stability and larger thermal conductivity because of additional graphene in shells. Nanoindentation tests showed this sample had the capability of deforming resistance under pressure coming from the composite structure of graphene/polymer structure. Moreover, more graphene decreased the penetrability of core material out of microcapsule shells.

Sensitive and selective determination of hydroxychloroquine in the presence of uric acid using a new nanostructure self-assembled monolayer modified electrode: optimization by multivariate data analysis

The Analyst ◽  
2014 ◽  
Vol 139 (16) ◽  
pp. 4064-4072 ◽  
Author(s):  
Asma Khoobi ◽  
Sayed Mehdi Ghoreishi ◽  
Mohsen Behpour
Keyword(s):  
Uric Acid ◽  
Self Assembly ◽  
Multivariate Data Analysis ◽  
Covalent Modification ◽  
Carbon Electrode ◽  
Self Assembled Monolayer ◽  
Selective Determination ◽  
Highly Sensitive ◽  
Electrochemical Nanosensor

A highly sensitive electrochemical nanosensor was developed using covalent modification of a glassy carbon electrode (GCE) by self-assembly of a novel Schiff base.

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