An electrochemical sensor for rapid determination of ractopamine based on a molecularly imprinted electrosynthesized o-aminothiophenol film

Cross-linked chitosan/thiolated graphene quantum dots as a biocompatible polysaccharide towards aptamer immobilization

Chitosan has a number of commercial and possible biomedical uses. Chitosan as a polysaccharide is a bioactive polymer with a variety of applications due to its functional properties such as antibacterial activity, non-toxicity, ease of modification, and biodegradability. In this work, cross-linked chitosan/thiolated graphene quantum dot as a biocompatible polysaccharide was modified by gold nanoparticle and used for immobilization of ractopamine (RAC) aptamer. A highly specific DNA-aptamer (5'-SH-AAAAAGTGCGGGC-3'), selected to RAC was immobilized onto thiolated graphene quantum dots (GQDs)-chitosan (CS) nanocomposite modified by gold nanostructures (Au NSs) and used for quantification of RAC. Different shapes of gold nanostructures with various sizes from zero-dimensional nanoparticles to spherical structures were prepared by one-step template-assistant green electrodeposition method. Fully electrochemical methodology was used to prepare a new transducer on a glassy carbon surface which provided a high surface area to immobilize a high amount of the aptamer. Therefore, a label free electrochemical (EC) apta-assay for ultrasensitive detection of RAC was developed. A special immobilization media consisting of Au NSs/GQDs-CS/Cysteamine (CysA) was utilized to improve conductivity and performance of the biosensor. The RAC aptamer was attached on the Au NSs of the composite membrane via AuS bond. The fabrication process of the EC aptamer based assay was characterized by some electrochemical techniques. The peak currents obtained by differential pulse voltammetry decreased linearly with the increasing of RAC concentrations and the apta-assay responds approximately over a wide dynamic range of RAC concentration from 0.0044 fM to 19.55 μM. The low limit of quantification was 0.0044 fM.

Ag–SnO2 nano-heterojunction–reduced graphene oxide by a stepwise photocatalyzed approach and its application in ractopamine determination

Stepwise reduction process for SnO₂–AgNPs–reduced graphene oxide under UV irradiation and its energy-band structure.

Electrochemical detection of ractopamine based on a molecularly imprinted poly-o-phenylenediamine/gold nanoparticle–ionic liquid–graphene film modified glass carbon electrode

An electrochemical sensor for sensitive detection of ractopamine (RAC) was fabricated by using molecularly imprinted polymer (MIP) incorporation with graphene (GR), ionic liquid (IL) and gold nanoparticle (AuNPs) nanocomposites.

Molecularly imprinted polymer decorated nanoporous gold for highly selective and sensitive electrochemical sensors

Electrochemical nanosensors based on nanoporous gold leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10(-11) to 1 × 10(-9) mol L(-1) and 1 × 10(-9) to 1.4 × 10(-6) mol L(-1) with a remarkably low detection limit of 1.8 × 10(-11) mol L(-1) (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples.

Preparation of ractopamine-tetraphenylborate complexed nanoparticles used as sensors to rapidly determine ractopamine residues in pork

In this work, we reported a simple, fast, and sensitive determination of ractopamine (RAC) residues in pork by using novel ractopamine-tetraphenylborate complexed nanoparticles (RT NPs) as sensors. The prepared RT NPs exhibited a fast response time of 10 s, a wide linear range from 0.1 to 1.0 × 10(-7) mol/L, and a very low detection limit of 7.4 × 10(-8) mol/L. The prepared sensor also presents a high selectivity for ractopamine under different pH conditions ranged from 2.85 to 7.18. These results reveal that the fabricated RT NPs can be used as efficient electrochemical sensors to determine ractopamine in animal productions.

A novel electrochemical sensor for the analysis of β-agonists: the poly(acid chrome blue K)/graphene oxide-nafion/glassy carbon electrode

A novel modified electrode was constructed by the electro-polymerization of 4,5-dihydroxy-3-[(2-hydroxy-5-sulfophenyl)azo]-2,7-naphthalenedisulfonic acid trisodium salt (acid chrome blue K (ACBK)) at a graphene oxide (GO)-nafion modified glassy carbon electrode (GCE). The characterization of an electrochemically synthesized poly-ACBK/GO-nafion film was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques, and the results were interpreted and compared at each stage of the electrode construction. Electrochemical oxidation of eight β-agonists - clenbuterol, salbutamol, terbutaline, ractopamine, dopamine, dobutamine, adrenaline, and isoprenaline, was investigated by CV at the different electrodes. At the poly-ACBK/GO-nafion/GCE, the linear sweep voltammetry peak currents of the eight β-agonists increased linearly with their concentrations in the range of 1.0-36.0 ng mL(-1), respectively, and their corresponding limits of detection (LODs) were within the 0.58-1.46 ng mL(-1) range. This electrode showed satisfactory reproducibility and stability, and was used successfully for the quantitative analysis of clenbuterol in pork samples.