Metallacarboranes as tunable redox potential electrochemical indicators for screening of gene mutation

Abstract

The substitution of hydrogen with chlorine in the metallacarborane [3,3-Fe(1,2-closo-C₂B₉H₁₁)₂]⁻ cluster modulates the formal potential of the Fe³⁺/Fe²⁺ redox couple, shifting it to a more positive value. Hence, very similar redox probes with a wide range of formal potentials, ranging from negative to positive values, are available. Thus, we have achieved the synthesis and studied the electrochemical behaviour of the sodium salt of [3,3-Fe(8,9,12-Cl₃-1,2-closo-C₂B₉H₈)₂]⁻ in aqueous media. This strategy allows tuning of the redox potential of the [3,3-Fe(1,2-closo-C₂B₉H₁₁)₂]⁻ framework with a minor change in its shape and dimensions. We also describe the interaction of the prepared [3,3-Fe(8,9,12-Cl₃-1,2-closo-C₂B₉H₈)₂]⁻ and the pristine [3,3-Fe(1,2-closo-C₂B₉H₁₁)₂]⁻ with DNA. These studies have been carried out not only with DNA in solution but also with DNA immobilized on screen-printed gold electrodes. The results obtained point to a strong interaction between the metallacarboranes and DNA, to a different extent with single stranded DNA (ssDNA) compared to double stranded DNA (dsDNA). This property makes them selective and wide-ranging potential electrochemical indicators of hybridization. The suitability of these new redox indicators for selective DNA biosensor development has been probed by the direct detection of two different mutations associated with cystic fibrosis in PCR amplicons extracted from blood cells.