Introducing common oxazine fluorophores as new redox labels for electrochemical DNA sensors

The electrochemical properties of three oxazine fluorophores, ATTO655, ATTO680 and ATTO700 have been investigated at gold electrodes. They display a reversible or quasi-reversible voltammetric behaviour involving either a 2e(-), 2H(+) or a 2e(-), 1H(+) redox process depending on the pH, at a formal potential located in the stability range of thiolate self-assembled monolayers (E degrees' approximate to-0.33 V vs. Ag|AgCl|3M KCl at pH 7.2). The performance of ATTO655 as redox label for electrochemical nucleic acid sensing was evaluated in a typical E-DNA configuration. The redox label has no detrimental impact on the folding of DNA, as shown with the i-motif forming sequence investigated here. An electron transfer rate constant around 40 s(-1) was determined, which is comparable to the values reported for the popular methylene blue label. Hybridisation experiments show a significant signal variation between ssDNA and dsDNA, though it is emphasised that the sign and amplitude of the variation are highly dependent on the electrochemical parameters such as the frequency in square wave voltammetry.

Automated summary

The electrochemical properties of three oxazine fluorophores, ATTO655, ATTO680 and ATTO700, were investigated on gold electrodes. These fluorophores exhibit reversible or quasi-reversible voltammetric behavior depending on the pH. ATTO655, in particular, showed promising performance as a redox label for electrochemical nucleic acid sensing without affecting DNA folding. Hybridization experiments showed significant signal variation between single-stranded DNA and double-stranded DNA.