Improved immobilization of DNA to graphite surfaces, using amino acid modified clays

Assessment of the interaction of small molecules with DNA, hybridization assays for DNA sequence analysis and diagnostics and the investigation of DNA damage involves the immobilization of an array of oligonucleotides onto a solid substrate. Herein, a new nano sized DNA-based biosensor containing valine (Val) amino acid organo-modified Cloisite Na⁺ as a new bionanohybrid film for the immobilization of DNA was developed. The Cloisite-Val organoclay was synthesized by a cation-exchange method, which involves the displacement of the sodium cations of Cloisite Na⁺ with the ammonium ions of the Val-amino acid. The synthesized materials were characterized with different methods such as FT-IR spectroscopy, TEM, SEM, XRD and electrochemical impedance spectroscopy (EIS). The nanostructured film was deposited at the surface of a working graphite electrode and utilized for the surface modification with double-stranded DNA. It was found that the electrode modification with DNA and Cloisite-Val leads to an enhanced sensitivity in the DNA voltammetric detection compared with other modified electrodes that were used for this work. The efficiency of DNA immobilization was followed by means of EIS and voltammetry. Immobilization is much more rapid when using the Cloisite-Val modified graphite support than when employing conventional supports. The stability of the immobilized DNA over several days has been found to be much higher when using the new support than in preparations using conventional ones.