Electrochemical biosensors are an increasingly attractive option for the development of a novel analyte detection method, especially when integration within a point-of-use device is the overall objective. In this context, accuracy and sensitivity are not compromised when working with opaque samples as the electrical readout signal can be directly read by a device without the need for any signal transduction. However, electrochemical detection can be susceptible to substantial signal drift and increased signal error. This is most apparent when analysing complex mixtures and when using small, single-use, screen-printed electrodes. Over recent years, analytical scientists have taken inspiration from self-referencing ratiometric fluorescence methods to counteract these problems and have begun to develop ratiometric electrochemical protocols to improve sensor accuracy and reliability. This review will provide coverage of key developments in ratiometric electrochemical (bio)sensors, highlighting innovative assay design, and the experiments performed that challenge assay robustness and reliability.

A novel ferrocene-based substrate for the ratiometric electrochemical detection of β-galactosidase was designed and synthesised. It was demonstrated to be an excellent electrochemical substrate for β-Gal detection with sensitivity as low as 0.1 U mL.

The high toxicity of phosphine and the use of organophosphines as nerve agent precursors has provoked the requirement for a rapid and reliable detection methodology for their detection. Herein, we demonstrate that a ferrocene-derived molecular probe, armed with an azidobenzene trigger, delivers a ratiometric electrochemical signal selectively in response to organophosphorus(III) compounds and can be accurately measured with an inexpensive, handheld potentiostat. Through an intensive assay optimization process, conditions were found that could determine the presence of a model organophosphine(III) nerve agent precursor within minutes and achieved a limit of detection for triphenylphosphine of just 13 ppm. Due to the portability of the detection system and the excellent stability of the probe in solution, we envisaged that this proof-of-concept of work could easily be taken into the field to enable potentially toxic organophosphorus(III) compounds to be detected at the point-of-need.

Complex stimuli responsive systems are synthetic analogues of natural cell environments, and the basis for molecular machines and computing. A dual psuedo-enantiomer system was concieved, where the combination of two...