Selectivity Of Electrochemical Detection Research Articles

A novel electrochemical aptasensor for exosomes determination and release based on specific host-guest interactions between cucurbit [7]uril and ferrocene

The superior supramolecular recognition ability of macrocyclic compounds will enhance the sensitivity and selectivity of electrochemical detection, which has a great application potential in electrochemical sensing. Herein, we developed a novel electrochemical aptasensor based on the specific host-guest interactions between cucurbit [7]uril and ferrocene (Fc) for capture, determination and release of exosomes. Macrocyclic compounds, cucurbit [7]uril is modified on the surface of the gold nanoparticles composed electrode by self-assembling. CD63 aptamer linked ferrocene is introduced into this platform to capture exosomes specifically by CD63 protein on the exosomes. The dual specificity of macrocyclic compounds and aptamers enables highly selective and sensitive electrochemical detection of exosomes. The limit of detection (LOD) was 482 particles μL-1. In addition, the captured exosomes could be released on demand in a very mild manner through aminoferrocene (NH2-Fc) because of its higher affinity to cucurbit [7]uril. The proposed electrochemical aptasensor showed good performance in detecting exosomes even in plasma samples, thus demonstrating its great potential in early clinical diagnosis. Simultaneously, exosomes could be released undamaged by this protocol, exhibiting good applicability in comprehensive studies of exosomes. Moreover, this strategy can be applied to other target biomolecules by changing the recognition pairs.

Voltammetric Determination of Dopamine in Human Serum with Amphiphilic Chitosan Modified Glassy Carbon Electrode

An improvement of selectivity for electrochemical detection of dopamine (DA)with differential pulse voltammetry is achieved by covalently modifying a glassy carbonelectrode (GCE) with O-carboxymethylchitosan (OCMCS). The amphiphilic chitosanprovides electrostatic accumulation of DA onto the electrode surface. In a phosphate buffersolution (pH 6.0), a pair of well-defined reversible redox waves of DA was observed at theOCMCS/GCE with a δEp of 52 mV. The anodic peak current obtained from thedifferential pulse voltammetry of dopamine was linearly dependent on its concentration inthe range of 6.0 × 10-8 to 7.0 × 10-6 M, with a correlation coefficient of 0.998. Thedetection limit (S/N = 3) was found to be 1.5 × 10-9 M. The modified electrode had beenapplied to the determination of DA in human serum samples with satisfactory results.

Internal standard method for the measurement of choline and acetylcholine by capillary electrophoresis with electrochemical detection

An internal standard method has been developed for the determination of the neurotransmitter acetylcholine and/or its metabolic precursor choline. This approach couples the high separation efficiency of capillary electrophoresis with the sensitivity and selectivity of electrochemical detection at an enzyme-modified electrode. Indirect electrochemical detection is accomplished at a 25 μm platinum electrode modified by cross-linking the enzymes choline oxidase and acetylcholinesterase with glutaraldehyde. Although in this simple form of electrode fabrication there is a gradual loss of response from the electrochemical detector with time, accurate quantitation is achieved by the addition of butyrylcholine, which is also a substrate for acetylcholinesterase, as an internal standard. A linear response is achieved between 0 and 125 μ M with a limit of detection of 2 μ M (25 fmol). The utility of this method was demonstrated by monitoring the kinetics of choline uptake in synaptosomal preparations.

Improvement of selectivity of electrochemical detection for the determination of compounds with chloro aromatic rings

Pharmaceuticals containing a thiazide ring or chlorinated aromatic ring were investigated with respect to enhanced selectivity in determination. Oxidative electrochemical detection coupled with HPLC was used to study the influence of the pH of the mobile phase under conditions of photolysis. To cover a pH range 3.9–12, the employment of a polymer column stable in alkaline media was necessary. The method offers the great advantage of derivatization without chemicals at low operating potentials, thereby providing high selectivity.