экология/6. Экологический мониторинг

Zaitseva A.S., Arlyapov V.A., Grishaeva A.R.

Tula State University

Development of biosensors based on modified SWCNTs and the immobilized glucose oxidase enzyme

To date, the actual development is the use of the modified single-walled carbon nanotubes (SWNTs) with carboxyl groups as a material for creating a highly sensitive biosensor based on the direct electron transfer (III generation). The perfect single-wall nanotube is a graphite cylinder in a folded plane formed by the regular hexagons, which are located at the vertices of carbon atoms. Depending on the angle of folding SWCNTs can have very different physical and chemical properties, such as conductivity, magnetism, strength, so they are widely used in nanoelectronics and nanomechanics.

The electroanalytical chemistry and biosensors are widely used electrodes made of carbon materials. Such electrodes have a wide range of polarization potentials, low background currents, good reproducibility and ease of regeneration signal of the working surface. Biosensors based on carbon nanotubes have high sensitivity and conductivity. The direct electron transfer is a way to mediator-less current registration of the substrate oxidation by direct oxidation of reduced enzyme on the electrode (Figure 1). This paper presents a biosensor based on modified SWCNTs using the glucose oxidase enzyme.

Fig. 1. Schematic representation of the work of the III generation biosensor with direct electron transfer based on modified SWCNTs and the glucose oxidase enzyme.

The advantage of using an enzyme is its high specificity, as well as direct electrical contact between the redox center of the enzyme and the electrode, and that allows the direct transfer of electrons. Initially, aging was carried out in a mixture of SWCNTs suspension of concentrated nitric and sulfuric acids (1:3) by treatment with ultrasound for 3 hours at room temperature (Figure 2). Ultrasound oxidation and split SWCNT causes increase their dispersibility in the solvent, and the possibility of joining in the field of functional groups fault.

Fig. 2. The oxidation (modification) of SWCNT mixture of acids under the influence of ultrasound.

Identification grafted functional groups carried on Fourier transform infrared spectrometer FSM 1201 ("Monitoring", Russia) in the infrared spectrum of the radiation. During prolonged sonication main product is the formation of carboxyl groups, which is the absorption spectrum in the range of 1714-1734 cm^-1, consistent with the literature (Weibel M. K., 1971).

Amperometric measurements made using a working carbon-paste electrode with directly deposited on the surface of the electrode slurry oxidized SWCNT and the enzyme glucose oxidase. The measurements were made at an operating potential -450 mV, which was selected by voltammetry. The resulting potential is consistent with the literature data (Wu X., 2009).

With the use of glucose as a substrate were determined metrological and analytical characteristics of modified SWCNTs biosensor. Long-term stability of the enzyme sensor was 9 days; range of detectable concentrations of glucose 0.024 - 1.000 mmol/dm³. Also, a comparison was made of certain characteristics of the developed biosensor based on modified single-wall CNTs with an analogue-based multi-walled CNTs (Rogaleva N. S., 2012). Features biosensor modified SWCNTs several times higher than those of similar biosensor MWCNTs: the minimum reporting level allows determining the lower concentration than that of a similar biosensor.

This work was supported by the grant of the President of the Russian Federation (contract № 14.Z56.16.5425-МК) and by the grant of the Russian Foundation for Basic Research (contract № 16-48-710959 р_а)

References:

Weibel M. K., Bright H. J. The glucose oxidase mechanism interpretation of the pH dependence //Journal of Biological Chemistry. 1971. V. 246. N. 9. PP. 2734-2744.

Wu X. et al. Direct electron transfer of glucose oxidase immobilized in an ionic liquid reconstituted cellulose–carbon nanotube matrix //Bioelectrochemistry. 2009. V. 77. N. 1. PP. 64-68.

Rogaleva N. S. et al. Amperometric biosensor modified with multiwalled carbon nanotubes for glucose determination // Biotechnologia Acta. 2012. V. 5. N. 1. PP. 53-61.