Advances in electrochemical and optical polyion sensing: A review

Electrochemical and optical sensing of polyions were first introduced in the early to mid 1990s via the development and study of the first heparin-sensitive potentiometric and optical polyion sensors. Since then, the number of reports relating to electrochemical and optical polyion sensing technologies have grown substantially. Both biologically and industrially relevant polyions can be detected using these methods. This paper provides an overview of key accomplishments with respect to polyion sensor-based technologies over the past 25+ years. A summary of the basic designs and sensing principles of single-use/fully reversible polymeric membrane-type potentiometric polyion sensors, voltammetric polyion-sensitive electrodes, and single-use polyion-sensitive optodes is provided. The expansion of polyion sensing to more industrial and cosmetic polyions (i.e., polyquaterniums) is also discussed. Lastly, potential new directions/applications are provided for electrochemical and optical polyion sensors based on all-solid-contact designs (for electrochemical) and paper-based sensing devices (both electrochemical and optical).