Search

Chiral selector-functionalized magnetic nanoparticles were achieved by self-assembly anchoring L-cysteine (L-Cys) on the surface of the Au/Fe 3 O 4 nanocomposites, which was synthesized via a facile in-situ reduction process. The as-prepared L-Cys-Au/Fe 3 O 4 magnetic nanoparticles (MNPs) were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy and electrochemical methods The typical MNPs with uniform globular morphology not only can provide the enhanced pore accessibility and excellent electrocatalytic active site for the guest species, but also effectively improve the load capacity of chiral selector of L-Cys. Based on magnetic field-induced assembly, a novel magnetic electrochemical chiral sensor (MECS) was first constructed by MNPs for the discrimination and determination of tyrosine (Tyr) enantiomers. Under the optimized experimental condition, the oxidation peak current ratio of L-Tyr to D-Tyr ( I L / I D ) and the difference between the peak potential of the two enantiomers (Δ E p = E D – E L ) was observed to be 1.85 and 84 mV according to square wave voltammetry (SWV). With the synergic effect of the magnetic Fe 3 O 4 NPs and the chiral electrocatalytic activity of L-Cys functionalized AuNPs, a linear relationship between the peak current and the concentration of the two enantiomers was obtained over the range of 1–125 μM, with the limit of detection of 0.021 μM and 0.084 μM for L- and D-Tyr, respectively. The preferential chiral recognition for L-Tyr was further verified by circular dichroism spectroscopy. Furthermore, the sensitive MECS has been successfully used for the practical determination of L- or D-enantiomer in the Tyr mixture solutions by continuously increasing the concentration of one isomer, showing the consistent and reproducible results. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new nanozyme Fe 3 O 4 @MoS 2 -Au NPs was designed and synthesized. • The dual-mode sensor based on Fe 3 O 4 @MoS 2 -Au NPs has multiple advantages. • Using the magnetic characteristics of nanozyme, real-time regulation of the catalytic reaction can be achieved. • 4. This research provides a new sensitive and accurate multi-channel analysis strategy for H 2 O 2 detection. Hydrogen peroxide (H 2 O 2) is closely related to many diseases and is often used as a target for disease diagnosis and treatment, so the research of H 2 O 2 detection method has attracted much attention. Compared with the current single-signal detection methods commonly used, dual-mode detection has inherent self-verification and self-correction functions and is expected to provide more reliable and anti-interference detection results. In this work, a novel nanocomposite Fe 3 O 4 @MoS 2 -Au NPs with strong peroxidase activity was constructed for the first time, and on this basis, a colorimetric/electrochemical dual-mode sensor was successfully prepared. Concretely, the Fe 3 O 4 @MoS 2 -Au NPs could catalyze reduction of H 2 O 2 to generate ·OH, leading to a significant electrochemical signal. At the same time, the color reaction of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) by ·OH can be used to build a colorimetric sensor. In colorimetric and electrochemical sensing systems, the linear range was 1–120 μM. The detection limit (LOD) can reach as low as 109 nM and 80 nM, respectively. In addition, the sensor has been favorably used for the detection of H 2 O 2 in normal human serum, and the recovery range was 87.55–113.13 %. In conclusion, this work provides an economical, sensitive and visualized H 2 O 2 detection platform, which has a wide application prospects. [ABSTRACT FROM AUTHOR]

Based on magnetic field directed self-assembly (MDSA) of the ternary Fe 3 O 4 @PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe 3 O 4 @PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe 3 O 4 @PANI into the graphene oxide layers via π–π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe 3 O 4 @PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N–H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe 3 O 4 @PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L −1 (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples. [ABSTRACT FROM AUTHOR]

Abstract: A novel electrochemical sensing platform based on magnetic field-induced self-assembly of Fe3O4@Polyaniline nanoparticles (Fe3O4@PANI NPs) has been for the first time fabricated for the sensitive detection of creatinine in biological fluids. The template molecule, creatinine, was self-assembled on the surface of Fe3O4@PANI NPs together with the functional monomer aniline by the formation of N–H hydrogen bonds. After pre-assembled, through the magnetic-induction of the magnetic glassy carbon electrode (MGCE), the ordered structure of molecularly imprinted polymers (MIPs) were established by the electropolymerization and assembled on the surface of MGCE with the help of magnetic fields by a simple one-step approach. The structural controllability of the MIPs film established by magnetic field-induced self-assembly was further studied. The stable and hydrophilic Fe3O4@PANI can not only provide available functionalized sites with which the template molecule creatinine can form hydrogen bond by the abundant amino groups in PANI matrix, but also afford a promoting pathway for electron transfer. The as-prepared molecularly imprinted electrochemical sensor (MIES) shows good stability and reproducibility for the determination of creatinine with the detection limit reached 0.35nmolL−1 (S/N=3). In addition, the highly sensitive and selective MIES has been successfully used for the clinical determination of creatinine in human plasma and urine samples. The average recoveries were 90.8–104.9% with RSD lower than 2.7%. [Copyright &y& Elsevier]

Abstract: Based on magnetic field directed self-assembly (MDSA) of Fe3O4@rGO composites, a novel magnetic molecularly imprinted electrochemical sensor (MIES) was fabricated and developed for the determination of the azo dye amaranth. Fe3O4@rGO composites were obtained by a one-step approach involving the initial intercalating of iron ions between the graphene oxide layers via the electrostatic interaction, followed by the reduction with hydrazine hydrate to deposit Fe3O4 nanoparticles onto the reduced oxide graphene nanosheets. In molecular imprinting, the complex including the function monomer of aniline, the template of amaranth and Fe3O4@rGO was pre-assembled through π–π stacking and hydrogen bonding interactions, and then was self-assembled on the surface of magnetic glassy carbon electrode (MGCE) with the help of magnetic field induction before electropolymerization. The structures and morphologies of Fe3O4@rGO and the doped molecularly imprinted polymers (MIPs) were investigated by Fourier transform infrared spectrometer (FT-IR), Raman spectra and scanning electron microscope (SEM). Besides, the characterization by differential pulse voltammetry (DPV) showed that Fe3O4@rGO composites promoted the electrical conductivity of the imprinted sensors when doped into the MIPs. The adsorption isotherms and adsorption kinetics were employed to evaluate the performances of MIES. The detection of amaranth was achieved via the redox probe K3[Fe(CN)6] by blocking the imprinted cavities, which avoided the interferences of oxidation products and analogs of amaranth. Furthermore, the prepared MIES exhibited good sensitivity, selectivity, reproducibility and efficiency for detecting amaranth in fruit drinks. The average recoveries were 93.15–100.81% with the RSD <3.0%. [Copyright &y& Elsevier]

Highlights: [•] The membrane of rGO/PANI was prepared for enhancing the sensitivity of sensor. [•] Functionalized AuNPs were proposed to fabricate the conductive AuNPs@MIPs. [•] The sensor could avoid the interferences caused by AA, DA, UA, and EP. [•] The sensor was used for sensitive and selective detection of 5-HT in real samples. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a highly sensitive and selective biomimetic electrochemical sensor for the amperometric detection of trace dopamine (DA) in human serums was achieved by gold nanoparticles (AuNPs) doped molecularly imprinted polymers (MIPs). Functionalized AuNPs (F-AuNPs), a novel functional monomer bearing aniline moieties on the surface of the AuNPs, were prepared via a direct synthesis method and then used to fabricate the conductive MIPs film on the modified electrode by electropolymerization method in the presence of DA and p-aminobenzenethiol (p-ATP). The obtained electrochemical sensor based on the conductive film of AuNPs doped MIPs (AuNPs@MIPs) could effectively minimize the interferences caused by ascorbic acid (AA) and uric acid (UA). The linear range for amperometric detection of DA was from 0.02μmolL−1 to 0.54μmolL−1 with the detection limit of 7.8nmolL−1 (S/N=3). Furthermore, the AuNPs@MIPs modified electrode (AuNPs@MIES) was successfully employed to detect trace DA in different human serums. [Copyright &y& Elsevier]

Abstract: In this paper, an electrochemical sensor for 17β-estradiol (E2) based on the molecular imprinting polymer (MIP) membranes had been constructed. 6-mercaptonicotinic acid (MNA) and E2 were first assembled on the surface of platinum nanoparticles-modified glassy carbon electrode (PtNPs/GCE) by the formation of Pt–S bonds and hydrogen-bonding interactions, and subsequently the polymer membranes were formed by electropolymerization. Finally, a novel molecularly imprinted sensor (MIS) was obtained after removal of E2. Experimental parameters such as deposition time, scan cycles, pH value and accumulation condition were optimized. Under optimal conditions, the MIS exhibited a large adsorption capacity and high selectivity. A good linearity was obtained in the range of 3.0×10−8–5.0×10−5 molL−1 (r =0.996) with an estimated detection limit of 1.6×10−8 molL−1. MIS had been successfully used to analyze E2 in water samples without complex pretreatment. Meanwhile, the average recoveries were higher than 93.9% with RSD<3.7%. All results above reveal that MIS is an effective electrochemical technique to determine E2 real-time in complicated matrix. [Copyright &y& Elsevier]