A benzimidazole-based new fluorogenic differential/sequential chemosensor for Cu2+, Zn2+, CN-, P2O74-, DNA, its live-cell imaging and pyrosequencing applications

Differential chemosensors have emerged as next-generation systems due to their simplicity and favourable responsive properties to produce different signals upon selective binding of various analytes simultaneously. Nevertheless, given their inadequate fluorescence response and laborious synthetic procedures, only a few differential chemosensors have been developed so far. In this work, we have employed a single pot synthesis strategy to establish a new benzimidazole-based Schiff base type fluorogenic chemosensor (DFB) which differentially detects Cu ²⁺ (detection limit (LOD) = 24.4 ± 0.5 nM) and Zn ²⁺ (LOD = 2.18 ± 0.1 nM) through fluorescence “off-on” manner over the library of other metal cations in an aqueous medium. The DFB-derived ‘in situ’ complexes DFB-Cu ²⁺ and DFB-Zn ²⁺ showed fluorescence revival “on-off” responses toward cyanide (CN ⁻) and bio-relevant pyrophosphate (P ₂O ₇ ^4--PPi) ions with a significantly low LOD of 9.43 ± 0.2 and 2.9 ± 0.1 nM, respectively, in water. We have demonstrated the phosphate group-specific binding capability of DFB-Zn ²⁺, by testing it with both ssDNA and dsDNA samples which displayed fluorescence “turn-off” response (LOD ∼10 ^-7 M), similar to the PPi binding in an aqueous medium, indicating that it interacts explicitly with the phosphate backbone of DNA. We have also harnessed the DFB as a sequential fluorescent probe to detect Cu ²⁺, Zn ²⁺, CN ⁻ and P ₂O ₇ ^4- ions in human cervical (HeLa) and breast (MCF-7 and MDA-MB-231 (aggressive and invasive)) cancer cell lines. Moreover, we have explored the PPi recognition capability of DFB-Zn ²⁺ in the polymerase-chain-reaction (PCR) products where PPi is one of the primary by-products during amplification of DNA.