Copper complex of a thienyl-hydrazone rhodamine derivative is a highly selective colorimetric sensor for pyrophosphate

Detection of pyrophosphate (PPi) can be used to monitor gene replication, transcription, and other forms of enzymatic DNA/RNA synthesis, but it can be difficult to perform in real samples because of the presence of many other biomolecules and buffer components. In this study we prepared a colorimetric probe that could detect PPi specifically and selectively in the presence of cysteine, dithiothreitol (DTT), nucleoside triphosphates, and human serum (containing several biomolecules and amino acids). Among four candidate rhodamine derivatives, we found that the copper complex 1 could detect PPi uniquely, even in the presence of several competing biomolecules. The copper complex 1 also exhibited its highly selective PPi sensing capability when applied to rolling circle amplification and in vitro transcription in samples containing high concentrations of DTT, making it a promising candidate for colorimetric detection of RNA/DNA when using amplification techniques.