Recent developments in molecular sensor designs for inorganic pyrophosphate detection and biological imaging

Inorganic pyrophosphate (PPi) is a key anion which plays a crucial role in an extensive range of biological and ecological processes. PPi is involved in many physiological reactions, including nucleic acid replication, chromosomal elongation, cell growth, energy storage and transduction, iron delivery, etc. It is the main causative factor for many bone joints diseases (e.g. pseudogout) and eutrophication related ecological issues. In recent years, PPi is conceived as one of the biological markers for various diseases, including cancer and infectious diseases and an essential target in diverse fields including ecological research. The quantification of PPi levels in live cells can offer critical information on metabolic processes, including DNA replication and tumour progression. Thus, development of new chemosensors for PPi opens up the opportunities to identify novel and promising diagnostic reagents for the genetic diseases and the monitoring of intracellular processes. A repertoire of colourimetric and fluorescent chemosensors for PPi has been developed yet, and many of them were not arrayed and explained in such a way to make the readers understand them comparatively. Therefore, in this critical review, we focused onthe design and function of some unsung chemosensors including metal-free, metal-based, sequential sensors, etc. for PPi detection via diverse binding mechanisms reported from 2010 to the end of the year 2019.