Scientists at the University of Florence and at the University of L'Aquila [Lozzi et al., doi: 10.1016/j.electacta.209.01.038] have successfully synthesised vertically aligned carbon nanotubes. A powerful genosensor was developed from this using synthetic oligonucleotides.

The carbon nanotubes (CNTs) were synthesised by thermal CVD which is a much more accessible method for carbon nanotube growth than some techniques as it only requires a basic tube furnace and gas manifold. It also has advantages in terms of sample sizes and numbers of samples that can be prepared per run.

Composite materials containing CNTs have currently drawn significant interest in devices, leading the nanotechnology. In biological sciences and engineering, CNTs/DNA composite has a special place not only in the field of biological sensors but also in other applications such as gene therapy. DNA can also be used to assist the dispersion and separation of CNTs .

Many genosensors have been developed employing carbon nanotubes as platform for DNA immobilization and electrochemical transduction. In particular, in the last five years, highly encouraging results have been obtained by modifying carbon electrode surfaces (mainly glassy carbon and carbon paste) with a dispersion of carbon nanotubes in polymers or solvents.

The vertical orientation of the nanostructures, facilitates the loading of DNA probe as well as the access of the analyte towards the immobilized probe, thus increasing the sensitivity of the analysis. Moreover, the technologies required for the construction of such surfaces are compatible with device miniaturization thus allowing the realization of nanoelectrodes or nanoarray, with a further increase in the sensitivity of the measurements. Despite these advantages, there has been limited success in developing the applications of well-oriented carbon nanotube films for DNA electrochemical biosensing.

In any sensor, conductivity is a function of different parameters like the constituent materials and that of different concentrations, humidity and temperature. The conducting species has to move through the CNTs and DNA with different conduction mechanisms, the sum of which gives rise to conductivity through the composite.

Highly sequence specific DNA analysis can be accomplished using this platform. The platform may also be applicable to the detection of trace redox chemicals (i.e. heavy metals, toxic contaminants, drugs, etc), immunoassay based detection scheme and as electrochemical detectors in microfluidic devices.