Zn2+ and Pyrophosphate Sensing: Selective Detection in Physiological Conditions and Application in DNA-Based Estimation of Bacterial Cell Numbers

A diformyl-quinoline based receptor (L 1 ) exhibits selective colorimetric and fluorometric sensing of Zn2+ in aqueous medium at pH 7.4 based on the intraligand charge transfer (ICT) process. The in situ formed phenoxo-bridged complex, L 1 ·2Zn can selectively and specifically sense PPi among all the other biologically important anions including ATP through reversible binding. The detection limit for Zn2+ and PPi were found to be approximately 56 and 2 ppb, respectively. The unique selectivity of the PPi by the L 1 -Zn ensemble could be used as an analytical tool to probe PPi generation in a prototype polymerase chain reaction (PCR) setup and track DNA amplification with higher sensitivity as compared to conventional agarose gel electrophoresis. Interestingly, the principle of PPi estimation in PCR rendered rapid estimation of bacterial cell numbers with a limit of detection of 10 CFU of Escherichia coli MTCC 433 in as early as 10 PCR cycles. The proposed method of PPi sensing offers interesting application potential in PCR-based rapid diagnostics for pathogenic agents and microbiological quality control.