Electrochemical Aptamer-Based Sandwich Assays for the Detection of Explosives

Analytical Chemistry (Impact Factor: 5.64). 04/2012; 84(10):4245-7. DOI: 10.1021/ac300606n
Source: PubMed


Electrochemical impedance spectroscopy (EIS) is used to detect 2,4,6-trinitrotoluene (TNT) in a novel sandwiched structure which relies on the specific interactions between (i) primary amine with TNT and (ii) TNT and anti-TNT aptamer. With pure targets, the assay has a sensitivity of 10(-14) M, a dynamic range of 10(-14)-10(-3) M, and employs a small sample volume (25 μL). The method's sensitivity is comparable to state of the art optical methods with the added advantages of electrochemical detection, which can be easily miniaturized and implemented into a hand-held device.

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    ABSTRACT: A simple aptasensor for sensitive and selective detection of acetamiprid has been developed based on electrochemical impedance spectroscopy (EIS). To improve sensitivity of the aptasensor, gold nanoparticles (AuNPs) were electrodeposited on the bare gold electrode surface by cycle voltammetry (CV), which was employed as a platform for aptamer immobilization. With the addition of acetamiprid, the formation of acetamiprid-aptamer complex on the AuNPs-deposited electrode surface resulted in an increase of electron transfer resistance (R(et)). The change of R(et) strongly depends on acetamiprid concentration, which is applied for acetamiprid quantification. A wide linear range was obtained from 5 to 600nM with a low detection limit of 1nM. The control experiments performed by employing the pesticides that may coexist or have similar structure with acetamiprid demonstrate that the aptasensor has only specific recognition to acetamiprid, resulting in high selectivity of the aptasensor. The dissociation constant, K(d) of 23.41nM for acetamiprid-aptamer complex has been determined from the differential capacitance (C(d)) by assuming a Langmuir isotherm, which indicates strong interaction between acetamiprid and aptamer, further proving high selectivity of the aptasensor. Besides, the applicability of the developed aptasensor has been successfully evaluated by determining acetamiprid in the real samples, wastewater and tomatoes.
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