**3.1. Carbon nanotubes (CNTs)**

pollutant agents or metals in the environment, investigation and evaluation of DNA-drug interaction mechanisms, detection of DNA base damage in clinical diagnosis, or detection of

Oxidative DNA damage caused by oxygen-free radicals lead to multiple modifications in DNA, including base-free sites and oxidized bases. The damage caused to DNA bases is potentially mutagenic [76] and can be enzymatically repaired. The interest lies in the sensitive determination and full characterization of the mechanism involved in oxidative damage to DNA bases. Electrochemical methods are used to study the DNA oxidative damage and in the investigation of the mechanisms of DNA-drug interactions. In recent study, it has been anticipated that the mispairs-coinage metal complexes can also be used as a biomarker [77].

The DNA-electrochemical biosensor enables pre-concentration of the hazard compounds which are investigated onto the sensor surface and *in situ* electrochemical generation of radical intermediates, which cause damage to the DNA immobilized on the electrode surface and

DNA has an optical response towards temperature, magnetic field, radiation and others. The flexibility of DNA can be modified by the radiations. When irradiated using gamma rays and neutrons (non-ionizing radiation), the dynamics of DNA macromolecules [78] changes its configuration when involved in environmental interactions with other components of the living cells [79]. Whenever any radiation passes through a semiconductor device, different effects are observed which depends on the range of energy of the particle (proton, alpha, neutron and both types of beta) and rays, such as gamma radiation [80]. These include defects as: vacancies, defect clusters, dislocation loops near the surface and adjustment of band gaps [81]. Electrical properties of DNA molecules can be understood by the electrical conduction mechanism, namely: thermionic emission, tunneling and hopping [82]. These all properties

Carbon Nanotubes (CNTs) has interesting physicochemical properties as electrical conductance, high mechanical stiffness, light weight, transistor behavior, piezoresistance, thermal conductivity, luminescence, electrochemical bond expansion as well as their versatile chemistry make them superb materials for a broad spectrum of applications ranging from energy

specific DNA sequences in human, viral and bacterial nucleic acids [72–75].

*2.2.5. Electrochemical biosensors for detection of DNA damage*

*2.2.4. DNA oxidative biomarker*

176 Green Electronics

can be electrochemically detected.

can be applied for DNA as radiation sensors.

storage devices, nanosensors and drug/gene delivery vehicles.

**3. Pure carbon aggregates**

*2.2.6. DNA as radiation sensors*

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure, a member of the fullerene structural family. Due to their extraordinary thermal conductivity, mechanical, and electrical properties, carbon nanotubes find applications as additives to various structural materials. The various representations of CNTs are given in **Figure 4**.
