ABSTRACT
A simple, low-cost and sensitive label-free aptasensor assembled with assisting reduced graphene oxide nanosheets as the signal amplifier was fabricated and applied for detecting ultra-low levels of Aflatoxin B1(AFB1) through a nano-bio interaction system. The conditions of different modified glassy carbon electrodes as the base of aptasensor were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The performance of the fabricated aptasensor was evaluated by FESEM, HRTEM and AFM images. The proposed biosensor detected AFB1sensitively in a wide linear range (0.5 nM-4µM) by DPV with a considerable low limit of detection (LOD = 0.07 nM) and good repeatability (RSD = 2.9) and stability. Finally, the present aptasensor was applied successfully for monitoring AFB1 with appropriate recoveries in pasteurized cow milk and human blood plasma as real samples.
Subject(s)
Aflatoxin B1/analysis , Aptamers, Nucleotide/chemistry , Biosensing Techniques/methods , Graphite/chemistry , Nanoparticles/chemistry , Aflatoxin B1/blood , Animals , Cattle , Dielectric Spectroscopy , Electrochemical Techniques/instrumentation , Electrochemical Techniques/methods , Electrodes , Female , Humans , Microscopy, Atomic Force , Milk/chemistry , Nanoparticles/ultrastructure , Oxides/chemistry , Reproducibility of ResultsABSTRACT
A selective and sensitive electrochemical sensor was studied for determination of levodopa (LD) in the presence of uric acid (UA) and ascorbic acid (AA) using poly-dianix blue and multi-walled carbon nanotubes (PDB/MWCNTs) modified glassy carbon electrode. Cyclic voltammetry, differential pulse voltammetry, and chronoamperometry methods were applied to investigate the electrocatalytic oxidation of LD, UA and AA in aqueous solutions. By DPV technique, LD, UA and AA give oxidation peaks at 0.380, 0.520 and 0.180 V, respectively. Under the optimized experimental conditions LD, UA and AA give a linear response in the range of 0.09-75 µmol L-1, 0.3-110 µmol L-1 and 10-160 µmol L-1, respectively. Accordingly, the obtained detection limits were 0.003, 0.002 and 0.023 µmol L-1. The method provides a simple electrochemical sensor for successful determination of LD in human blood serum samples.
Subject(s)
Ascorbic Acid/chemistry , Electrodes , Levodopa/analysis , Nanotubes, Carbon/chemistry , Uric Acid/chemistry , Hydrogen-Ion Concentration , Oxidation-ReductionABSTRACT
Immobilization of L-lysine alpha-oxidase on gold-mercaptopropionic acid self-assembled monolayer (Au-MPA-LOx SAM) electrode is verified experimentally in the present work. Fabrication steps and electrochemical interaction of Au-MPA-LOx with L-lysine were monitored by general electrochemical methods like cyclic voltammetry (CV) and chronoamperometry (CA), and by a more advanced method, electrochemical impedance spectroscopy (EIS) in the presence of parabenzoquinone (PBQ) redox probe. The data was analyzed from which quantitative kinetic parameters were extracted. The results confirmed successful immobilization of LOx, and thus, fabrication of Au-MPA-LOx SAM electrode. Our initial tests revealed a linear response for Au-MPA-LOx SAM electrode toward L-lysine concentration in solution at biological conditions, pH 7.4. The experimental data will be presented and discussed from which the Au-MPA-LOx SAM electrode is characterized, and the kinetic merits of the interface interactions are introduced.
Subject(s)
3-Mercaptopropionic Acid/chemistry , Amino Acid Oxidoreductases/chemistry , Biosensing Techniques/methods , Electrochemistry/methods , Gold/chemistry , Lysine/analysis , Biosensing Techniques/instrumentation , Electrochemistry/instrumentation , Electrodes , Enzymes, Immobilized/chemistryABSTRACT
Preparation and application of gold 2-mercaptosuccinic acid self-assembled monolayer (Au-MSA SAM) electrode for determination of iron(III) in the presence of iron(II) is described by cyclic voltammetry, electrochemical impedance spectroscopy, and Osteryoung square wave voltammetry. The square wave voltammograms showed a sharp peak around positive potentials +0.250 V that was used for construction of the calibration curve. Parameters influencing the method were optimized. A linear range calibration curve from 1.0x10(-10) to 6.0x10(-9) M iron(III) with a detection limit of 3.0x10(-11) M and relative standard deviation (R.S.D.) of 6.5% for n=8 at 1.0x10(-9) M iron(III) was observed in the best conditions. Possible interferences from the coexisting ions were also investigated. The results demonstrated that sensor could be used for determination of iron(III) in the presence of various ions. The validity of the method and applicability of the sensor were successfully tested by determining of iron(III) in natural waters (tap and mineral waters) and in a pharmaceutical sample (Venofer ampoule) without interference from sample matrix. The experimental data are presented and discussed from which the new sensor is characterized.
