Supramolecular confinement of polymeric electron transfer mediator on gold surface for picomolar detection of DNA

In this work, we describe a novel route for the immobilisation of an electron transfer mediator on electrode surfaces based on the interfacial complexation of a bifunctionalised carboxymethylcellulose (CMC) polymer backbone bearing ferrocene units and a DNA probe on a cyclodextrin-functionalised surface. The interfacial self-assembly has been studied using surface plasmon resonance and electrochemical techniques and the applicability of the modified surface for the construction of an amperometric genosensor was explored for the detection of a celiac disease associated allele. The supramolecular strategy simplifies the operation of the biosensor, only requiring the addition of an enzyme substrate, and the proximity of the mediator to the electrode surface greatly improves the detection limits attained (10 pM) with respect to a similar supramolecular system based on electrochemically inactive adamantane/CD inclusion complexes (80 pM) and requiring addition of the mediator in solution. In addition, the use of the hydrophilic CMC backbone contributes to the elimination of non-specific interactions and to an optimal spacing of the immobilised DNA probes.