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Food Chem ; 304: 125397, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31479996


Branched polyethyleneimine functionalized reduced graphene oxide (BPEIGn) was prepared by a one-step reaction, catalyzed by NaOH, using branched polyethyleneimine (BPEI) and graphene oxide (GO) without reductant hydrazine hydrate or sodium borohydride. The branched polyethylenimine acted as both a grafting agent and a reducing agent of GO. An competitive electrochemical immunosensor based on the Au/sodium mercaptopropanesulfonate/BPEIGn/gold nanoparticles/melamine (Au/MPS/BPEIGn/AuNPs/Mel) modified electrode was constructed for the determination of melamine. The double amplification of BPEIGn and AuNPs increased the sensitivity of the sensor. The melamine was detected by differential pulse voltammetry (DPV) in buffer solution (pH 7.4) containing K3(Fe(CN)6]/K4[Fe(CN)6]. Under optimized conditions, the proposed melamine immunosensor showed a linear relationship in the concentration range of 1 × 10-6 to 1 µM, with a detection limit of 2.66 × 10-7 µM.

Biosens Bioelectron ; 100: 445-452, 2018 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-28961547


A new near-infrared electrochemiluminescence resonance energy transfer (NECL-RET) strategy for enzyme-free amplified DNA detection was designed. In this strategy, the quaternary Cu-Zn-In-S nanocrystals (NCs) were applied as the ECL donor and gold nanostars (AuNSs) were used as the acceptor. The flowerlike MoS2/GO/o-MWNTs nanostructure was synthesized and used as an outstanding substrate to immobilize the NCs. ECL measurements demonstrated that the NCs assembled on the MoS2/GO/o-MWNTs film resulted in ECL intensity amplified by ~2.5-fold compared to that of the NCs assembled directly on the GCE. The Sem used here was not only as a coupling reagent to attach the NCs on the MoS2/GO/o-MWNTs but also as a novel co-reaction accelerator to enhance the ECL intensity. In addition, we designed two hairpin DNA probes of H1 and H2, and based on the target-catalyzed hairpin assembly, tDNA could trigger the hybridization of the H1 and H2-AuNSs to be further released to initiate the next hybridization process to capture a larger number of H2-AuNSs on the electrode surface, which resulted in the quenching of the NCs ECL emission. Therefore, a dramatic increase in the ECL quenching efficiency proportional to the tDNA concentration was achieved. The linear range for tDNA detection was from 10aM to 10pM with a detection limit down to 10aM. This design introduces the new concept of triple signal amplification into ECL determination, and it shows promise to be extended to provide a highly sensitive platform for various target DNA.

Cobre/química , DNA/genética , Índio/química , Medições Luminescentes/métodos , Nanopartículas/química , Técnicas de Amplificação de Ácido Nucleico/métodos , Zinco/química , Tirosina Quinase 3 Semelhante a fms/genética , Técnicas Biossensoriais/métodos , DNA/análise , DNA Bacteriano/análise , DNA Bacteriano/genética , Técnicas Eletroquímicas/métodos , Ouro/química , Humanos , Nanopartículas/ultraestrutura , Nanotubos de Carbono/química , Nanotubos de Carbono/ultraestrutura , Enxofre/química
Mater Sci Eng C Mater Biol Appl ; 68: 308-316, 2016 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-27524025


The triethylenetetramine-functionalized graphene (TFGn) was prepared using graphene oxide (GO) and triethylenetetramine as raw materials through a one-step reaction under alkaline condition. The triethylenetetramine not only acted as cross-linker to combine GO, but also as reductant of GO. The TFGn was characterized by its ultraviolet spectrum (UV), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM). The results showed that triethylenetetramine was successfully grafted onto the surface of the GO through covalent bonding between amine and epoxy groups. The resultant TFGn was uniformly dispersed in water over several weeks, suggesting that the introduction of amino groups greatly increased the hydrophilicity of TFGn. The triethylenetetramine-functionalized graphene was then applied to fabricate glucose biosensors with IO4(-) oxidized glucose oxidase (GOx) through layer-by-layer (LBL) self-assembly by the covalent bonding between the aldehyde groups of GOx and amino groups of TFGn. The gold electrodes modified with the (GOx/TFGn)n multilayer films were studied by cyclic voltammetry (CV) and showed outstanding electrocatalytical response to the oxidation of glucose when ferrocenemethanol was used as an artificial redox mediator. The response increased with an increasing number of GOx/TFGn bilayers, indicating that the analytical performance, such as the sensitivity of the glucose biosensor, could be adjusted by tuning the number of deposited GOx/TFGn bilayers. The linear response range of the biosensor constructed with six bilayers of GOx/TFGn to the concentration of glucose can extend to at least 8mM with a sensitivity of 19.9µAmM(-1)cm(-2). In addition, the sensor exhibited good stability due to the covalent interactions between the GOx and TFGn.

Técnicas Biossensoriais/métodos , Glucose Oxidase/química , Glucose/análise , Grafite/química , Trientina/química
Biosens Bioelectron ; 78: 7-13, 2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-26584077


An isothermal, enzyme-free and sensitive electrochemical DNA sensor was developed for the detection of the FLT3 gene in acute myeloid leukemia (AML). First, aminated multi-walled carbon nanotubes (AMWNTs) and gold nanoparticles (AuNPs) were alternately self-assembled on a gold electrode using a layer-by-layer strategy. Then, the hairpin DNA probe 1 (H1), with a thiol group at the 3' end and a ferrocenyl moiety (Fc) at the 5' end, was immobilized on the AMWNTs/AuNPs multilayer films through Au-S bonding. When the target DNA (TD) appeared, it hybridized with and opened the hairpin structure of H1, and Fc was forced away from the electrode surface, leading to a significant decrease in the current peak of square wave voltammetry. Subsequently, the hairpin DNA probe 2 (H2) bound to H1, freeing the TD to trigger another reaction cycle. The combination of this target-catalyzed hairpin assembly and the LBL assembly of nanomaterials achieved a detection limit of 0.1 pM with a wide linear range of 0.1-1000 pM. The sensor discriminated between mismatched DNA and the target DNA with high selectivity. This dual signal amplification strategy is relatively simple and inexpensive because it does not need any enzymes or sophisticated equipment and successfully assayed the FLT3 gene from real samples.

Técnicas Biossensoriais/métodos , Leucemia Mieloide Aguda/diagnóstico , Nanotubos de Carbono/química , Tirosina Quinase 3 Semelhante a fms/isolamento & purificação , Técnicas Eletroquímicas/métodos , Ouro/química , Humanos , Leucemia Mieloide Aguda/genética , Limite de Detecção , Nanopartículas Metálicas/química , RNA Interferente Pequeno/química , RNA Interferente Pequeno/genética , Tirosina Quinase 3 Semelhante a fms/genética
Biosens Bioelectron ; 39(1): 289-95, 2013 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-22921947


This study demonstrates a polyelectrolyte-free method to fabricate controllable and stable all-MWNTs films via a covalent layer-by-layer (LBL) deposition. Aminated MWNTs and carboxylated MWNTs were prepared by surface functionalization, allowing the incorporation of MWNTs into highly tunable thin films through the formation of covalent amide bonds. Fourier transform infrared spectroscopy (FTIR) analysis demonstrated the formation of covalent linkages between MWNTs layers. Scanning electron microscopy (SEM) and ultraviolet-visible spectroscopy (UV-vis) were used to characterize the assembly process. Electrochemical studies indicated that the all-MWNTs film possessed a remarkable electrocatalytic activity toward dihydronicotinamide adenine dinucleotide (NADH) at relatively low potentials, without the need for redox mediators. The film thickness and the amount of assembled MWNTs were readily adjusted by simply changing the number of cycles in the LBL assembly process, which also effectively tuned the electrocatalytic activity of the film toward NADH. The film constructed with four bilayers showed a high sensitivity of 223.8µA mM(-1)cm(-2) and a detection limit of 1.5µM, with a fast response of less than 3s. Furthermore, the all-MWNTs film also showed good selectivity and excellent stability for the determination of NADH.

Técnicas Biossensoriais/métodos , NAD/análise , Nanotubos de Carbono/química , Catálise , Técnicas Eletroquímicas/métodos , Oxirredução , Sensibilidade e Especificidade