Electrodes aptasensor development

Metal NPs were also used as labels to follow aptamer-substrate interactions. The supramolecular self-organization of the aptamer-substrate complexes on surfaces was implemented to develop different configurations of electrical aptasensors.88 The anticocaine aptamer was separated into two fragments (37 and 38) (Fig. 12.24a). The nucleic acid (37) was assembled on a Au electrode, whereas the nucleic acid (38) was... 

A reusable electrochemical electrode for the use of low-molecular-weight molecules by its aptamers was demonstrated with the development of an electrochemical aptasensor for adenosine monophosphate (Wu et al., 2007). The anti-adenosine aptamer was functionalized at its end with a redox-active ferrocene unit. An electrode was functionalized with nucleic acid complementary to a region of the aptamer, and this was hybridized to the redox-tethered aptamer, giving rise to a redox response. In the presence of adenosine, an adenosine-aptamer complex was formed, resulting in dissociation of the redox-tethered aptamer from the surface and depletion of the redox signal. The extent of the decrease in electrical response was controlled by concentration of the adenosine analyte. 

Also, the pyrroloquinoUne quinone-dependent glucose dehydrogenase (GDH) was employed as a biocatalytic label for the amplified amperometric detection of thrombin (Figure 3.4C) (Ikebukuro et al., 2005). The fact that two different DNA aptamers bind to thrombin (Bock et al., 1992 Padmanabhan et al., 1993 Tasset et al., 1997) was utilized to develop the aptasensor for thrombin. Thrombin was linked to a 15-mer thiolated aptamer linked to a gold electrode, and the GDH-avidin conjugate was linked to the surface by its association to the biotinylated 29-mer aptamer bound as a secondary aptamer to the thrombin on the surface. The bioelectrocatalyzed oxidation of glucose in the presence of... 

Electrochemical aptasensors have been developed widely for some period of time, especially in the most recent few years (Willner and Zayats, 2007). Due to the properties of the technique itself, most electrochemical aptasensors depend on electrodes for electron transfer. Thus, the SOALF mode could make sense. Here we introduce mainly easy routes in this mode rather than in the SFALF mode. 

Fig. 14 Schematic diagram for the principle of the developed ECL aptasensor for detecting thrombin. (A) The adsorption of thiolated antithrombin aptamer on and the 2-mercapto-ethanol block to the electrode. (B) The formation of the dsDNA between aptamer and its complementary ssDNA. (C) The intercalation of Ru(phen)3 into the dsDNA sequence. (D) Dissociation of dsDNA and release of Ru(phen)3 due to the interaction between thrombin and its aptamer. Reprinted with permission from Ref 97. Copyright (2009) American Chemical Society.

Another aptasensor based on the displacement of a complementary strand from an aptamer was developed for the detection of ATP by coupling this approach to signal amplification by Au-NPs [50]. In this work the hybrid was formed by a reporter DNA labeled with Au-NPs, a thiol-modified DNA anchored to an electrode and a target-responsive DNA (the aptamer) (Fig. 2.10). Moreover, [Ru(NH3)e] ... 

Aptamer-based biosensors, also called aptasensor have gain a wide interest in the last years due to the advantages of aptamers compared to antibodies. Similar to antibodies, a variety of immobilization methods is available to bind aptamers to the sensor element. Aptasensors can be coupled to an electrochemical, optical or mass-sensitive transducer [13]. One of the successful examples for aptasensor was the detection of thrombin which was widely investigated [14]. Xiao et al. [15] have made an interesting development a redox compound (methylene blue) was inserted into the thrombin aptamer. When the target bound to the aptamer, the induced conformation change inhibited the electron transfer from the methylene blue to the electrode. This change could be detected amperometrically. 

Xiao et al. (2005a) developed a label signal-ofl aptasensor for the detection of THR in blood serum. The aptamer against THR was immobilized onto a gold electrode by chemisorption. Before binding to the protein, the 3 -end MB-label aptamer is close... 

On the other hand, Ocafia et al. (2012) reported a simple, label-free impedimetric aptasensor for the detection of THR in PBS buffer solutions. In the design of the aptasensor, a graphite epoxy composite was used and the aptamers were immobilized onto the electrode surface by physical adsorption. A detection limit of 4.5 pM was achieved using EIS in the presence of the [Fe(CN) ] " redox probe. The aptasensor was regenerated for several cycles. Recently, Liu et al. (2015) developed an impedimetric aptasensor, using AuNPs for signal amplification and the redox probe [Fe(CN) ] , for detection and quantification of MUCl in PBS buffer solutions. 

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