Application of nanostructured ZnO films for electrochemical DNA biosensor

Nanostructured zinc oxide (nsZnO) films have been fabricated onto conducting indium–tin–oxide (ITO) coated glass plate, by cathodic electro-deposition to immobilize probe DNA specific to M. tuberculosis via physisorption based on strong electrostatic interactions between positively charged ZnO (isoelectric point = 9.5) and negatively charged DNA to detect its complementary target. Electrochemical studies reveal that the presence of nano-structured ZnO results in increased electro-active surface area for loading of DNA molecules. The DNA–nsZnO/ITO bioelectrode exhibits interesting characteristics such as detection range of 1 × 10−6 − 1 × 10−12 M, detection limit of 1 × 10−12 M (complementary target) and 1 × 10−13 M (genomic DNA), reusability of about 10 times, response time of 60s and stability of up to 4 months when kept at 4°C.