Abstract
The increasing application of aptamers in bioassays has triggered a lot of research interest for development of highly sensitive and selective sensing platforms. Herein, we report on the design of a sensitive cocaine biosensor by immobilizing the 5′-disulfide-functionalized end of an aptamer sequence on a nanoporous gold (NPG) electrode followed by the conjugation of its 3′-amino-functionalized end to 2,5-dihydroxybenzoic acid (DHBA) as the redox probe. In the presence of cocaine, the aptamer undergoes a conformational change from an open unfolded state to a closed conformation, which reduces the distance between DHBA and the electrode surface, resulting in the enhanced electron-transfer efficiency. Using square wave voltammetric method and under the optimal conditions, the cocaine aptasensor presented two linear responses in the concentration ranges between 0.05–1 and 1–35 μM, with an excellent detection limit of 21 nM. The proposed aptasensor provides a simple and low-cost method for cocaine detection with good reproducibility and accuracy. Furthermore, it could be regarded as a general model to investigate the unique function of aptamer-functionalized nanostructured electrodes to stablish highly advanced electrochemical biosensors for various target analytes of diagnostic importance.
Highlights
Drug abuse continues to be a growing global concern, causing serious health and economic implications worldwide.[1,2] Cocaine, known as benzoylmethylecgonine, is one of the most widely abused drugs all over the world and is known to be a strong stimulant to the central nervous system.[3]
Several analytical methods have been developed for determination of cocaine, including high performance liquid chromatography,[6,7] gas-chromatography-mass spectrometry,[8] ion mobility spectrometry,[9,10,11] surface-enhanced Raman scattering spectroscopy,[12,13] chemiluminescence,[14] uorescence,[15,16] colorimetry[17,18] and piezoelectric.[19]
Electrochemical biosensors have been proved to have the advantages of being inexpensive, easy to use, rapid and robust compared to the other methods for cocaine detection.[20,21]
Summary
Drug abuse continues to be a growing global concern, causing serious health and economic implications worldwide.[1,2] Cocaine, known as benzoylmethylecgonine, is one of the most widely abused drugs all over the world and is known to be a strong stimulant to the central nervous system.[3]. Aptamers are short single-stranded nucleic acid oligomers that have attracted a lot of research interest, owing to their outstanding and unique properties including small size, ease of synthesis, low immunogenicity, high binding speci city, high resistance against denaturation, stability over wide temperature and pH ranges and fast refolding to the original structure.[22] In the past two decades, aptamer-based biosensors with high speci city and affinity have become a signi cant diagnostic tool for capturing and detection of a wide number of analytes ranging from small molecules,[23,24] ions,[25,26] peptides,[27] proteins[28] and cells.[29] Nanotechnology has been widely used as an efficient tool to improve the sensitivity of all kinds of sensors and biosensors including aptasensors by signal ampli cation on a wide variety of nanomaterials and nanostructures such as metal nanoclusters and nanoparticles,[30,31,32] electrospun nano bers,[33,34] conjugated polymers[35,36,37] and carbon-based materials.[38] The integration of electrochemical detection techniques with aptamer- and nano-technologies is a unique combination, enabling the development of highly advanced sensing platforms for detection of almost all kinds of target analytes in a sensitive, selective, fast and reliable manner. It was showed that under the optimal conditions the proposed aptasensor could be effectively used for sensitive and selective detection of cocaine
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