Aptasensor for Thrombin Based on Carbon Nanotubes‐Methylene Blue Composites

Abstract

The amperometric and EQCM aptasensors based on DNA aptamers immobilized by avidin-biotin method or by electrostatic adsorption onto multiwalled carbon nanotube layer contained methylene blue (MB) have been developed and examined for thrombin detection in buffer and in spiked blood serum. The presence of MB increases the binding capacity of the surface layer and enhances the range of thrombin concentrations to be determined. This results in significant improvement of analytical characteristics of thrombin detection. The EQCM aptasensors allowed us to detect 0.3 -100 nM and amperometric aptasensors 10 -1000 nM of thrombin.

Impedimetric Aptasensors Based on Carbon Nanotubes – Poly(methylene blue) Composite

“…Other experimental conditions for MB polymerization have been established previously [27] for amperometric DNA sensors of similar architecture. Here, the same concentration, i.e.…”

“…BIOFIBRI: 5'-GGT TGG TGT GGT TGG (A) 9 (T) 18 -3'-Biotin FIBRI: 5'-(A) 27 GGT TGG TGT GGT TGG-3' COMP:…”

“…MWNTs were dispersed in dimethylformamide (DMF) as described elsewhere [27]. Briefly, 1 mg of MWNTs was mixed with 1 mL of the mixture of concentrated H 2 SO 4 and HNO 3 in 3 : 1 ratio (v/v) and sonicated at 40 8C for 4 h (Tesla ultrasonic bath, 40 W).…”

Potential uses of G-quadruplex-forming aptamers

“…Electrochemical quartz crystal microbalance (EQCM), the combination of QCM with electrochemical measurements, has also been shown to be very effective. We applied EQCM to thrombin specific aptasensors based on MWCNTs-MB (multi-walled carbon nanotubes-methylene blue) composite (Evtugyn et al 2008b) (Fig. 12A).…”

“…Fluctuations in the oscillation frequency of the quartz crystal which reflect both mass and viscosity changes at the crystal surface were measured during cycling of the voltage in the range of -0.7 to + 0.6 V (vs. Ag/AgCl reference electrode) a process which aided the interaction between thrombin and the DNA aptamers. This method has substantially improved the thrombin detection limit; while conventional QCM methods with aptamers immobilized by avidin-biotin technology resulted in thrombin detection with a LOD of 10 nM (Hianik et al 2005), the immobilization of aptamers on the MWCNTs-MB composite layer and simultaneous cycling of the voltage resulted in a LOD of 0.3 nM (Evtugyn et al 2008b;Hianik et al 2008). In our work we showed higher sensitivity of aptasensor based on aptamer dimers (aptabodies) in comparison to the conventional single-stranded aptamers (Fig.…”