Electrochemical sensors with carbon nanotubes for biomedical research

Abstract

The results of the development of electrochemical sensors with carbon nanotubes are pre sented. A systematic classification of the sensors according to their design features is suggested; their analytical characteristics are evaluated and their potential for use in biomedical research is shown.ELECTROCHEMICAL SENSORS WITH CARBON NANOTUBES 53 nophen occurring in the sample, as well as a linear dependence of the signal on the concentration of this chemical compound [10]. Carbon nanotubes of the sensor can be treated in order to modify their surface with functional groups. This is the approach that Lin et al. used in the development of an amperometric device for determining glucose. Glucose oxidase was immobilized at the ends of the carbon nanotubes of the sensor by forming amide bonds between N acetylglucosamine residues and carboxyl groups of the modified nanotubes. Under the catalytic action of glucose oxidase, glucose was oxidized by oxygen, while the products of the enzymatic reaction were gluconic acid and hydrogen peroxide:.( 1 ) According to Eq. (1), the concentration of the resulting hydrogen peroxide is proportional to the con centration of glucose; therefore, the signal of the sensor caused by the appearance of hydrogen peroxide in the sample was a characteristic of the glucose concentration. In addition, such chemical compounds as acetaminophen, uric acid, and ascorbic acid had no effect on the signal of the sensor [7].Sensors based on carbon nanotube arrays can also be used in the analysis of DNA or RNA. In this case, the nanotubes of the sensor are modified with oligonucleotides, in particular, guanine. This is explained by the ability of oligonucleotides to easily bond with the corresponding complementary nucleotides of DNA and RNA. To measure the signal corresponding to the presence of DNA and RNA in a sample, the complex compound [Ru(bpy) 3 ] 2+ is used, indicating the oxidation of guanine. Reduced density of carbon nanotubes on the surface of the sensor leads to an increase in sensitivity [11,12].