Barun Kumar Datta

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

A diformyl-quinoline based receptor (L1) exhibits selective colorimetric and fluorometric sensing of Zn(2+) in aqueous medium at pH 7.4 based on the intraligand charge transfer (ICT) process. The in situ formed phenoxo-bridged complex, L1·2Zn can selectively and specifically sense PPi among all the other biologically important anions including ATP through reversible binding. The detection limit for Zn(2+) and PPi were found to be approximately 56 and 2 ppb, respectively. The unique selectivity of the PPi by the L1-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.

A simple and efficient fluorophoric probe for dual sensing of Fe3+ and F−: application to bioimaging in native cellular iron pools and live cells

A new quinoline functionalized fluorophoric Schiff base L1 was synthesized and its colorimetric and fluorescence responses toward various metal ions in mixed aqueous media were explored. The ligand exhibited high selectivity towards Fe3+ in the presence of a large excess of other competing ions with certain observable optical and fluorescence changes. These spectral changes are significant enough in the visible region of the spectrum and thus enable naked eye detection. The efficiency of L1 in detecting Fe3+ ions was also checked in the presence of relevant complex biomacromolecules viz. methaemoglobin, fetal bovine serum and human serum albumin. L1 was also found to be sensitive enough for visual detection of Fe3+ ions in native iron pools of banana pith. Studies revealed that L1–Fe complex formation is fully reversible in the presence of the fluoride anion with very high selectivity. Furthermore, fluorescence microscopic studies demonstrated that compound L1 could also be used as an imaging probe for detection of uptake of these ions in model human cells. This selective sensing behaviour of L1 towards Fe3+ was explained via the CHEF process where theoretical calculations also supported the premise.

Binding discrepancy of fluoride in quaternary ammonium and alkali salts by a tris(amide) receptor in solid and solution states

A dinitrophenyl functionalized tris(amide) receptor, L, showed distinct complexation behaviour towards the F− anion when tetrabutylammonium fluoride (TBAF) and potassium fluoride (KF) salts were individually employed for the recognition of F− with L. X-ray crystallography analyses revealed the formation of a F−–encapsulated complex (1 : 1 host–guest) stabilized by three N–H⋯F− and three C–H⋯F− hydrogen bonds when TBAF was employed as the F− source, whereas in the KF complex of L (1 : 1 host–guest), the receptor is involved in side-cleft binding of a hydrated KF contact ion-pair governed by amide N–H⋯F−, aryl C–H⋯F− and lp(F−)⋯π interactions. The binding of hydrated KF is identical to the side-cleft binding of solvents such as DMSO and DMF via N–H⋯O, aryl C–H⋯O and lp(O) ⋯π interactions, which has been exemplified by X-ray crystallography and a detailed Hirshfeld surface analyses of the crystals. The binding discrepancy of F− in the TBAF and KF complexes of L has also been manifested in the solution state by 1H NMR and 2D NOESY NMR experiments. In the 1H NMR analyses, a huge downfield shift of the coordinating –NH and ortho–CH protons was observed in the TBAF complex in comparison to the KF complex whereas, in the 2D NOESY NMR experiments, a disappearance of the signals corresponding to the through-space NOE coupling between the –NH and ortho–CH protons was observed in the former when compared to the latter and free receptor, L.

A near-infrared emissive Al3+ sensing platform for specific detection in solution, cells and probing DNase activity

A new tricarbocyanine-based chemosensor exhibited a dramatic Al(3+)-specific fluorescence turn-on response in the near-infrared (NIR) region. The receptor was found to be highly selective towards Al(3+) over other metal ions in physiological condition. The sensor was non-toxic and could thus be employed as an imaging probe for detecting intracellular Al(3+) in live cells. Interestingly, upon interaction with DNA in solution, the L-Al(3+) ensemble rendered tracking of DNase activity in solution through a systematic reduction in the fluorescence emission intensity.

Fluorescent naphthalene-based benzene tripod for selective recognition of fluoride in physiological condition

AbstractAluminium complex of a naphthalene-based benzene tripod ligand system has been reported for the selective recognition of fluoride in aqueous medium in physiological condition. The ligand can selectively recognize Al3+ through enhancement in the fluorescence intensity and this in situ formed aluminium complex recognizes fluoride through quenching of fluorescence. The receptor system detects fluoride in nanomolar range. The sensing property was extended for practical utility to sense fluoride in tap water, pond water and river water. Graphical AbstractA highly fluorescent tripodal aluminum complex was used for the sensing of fluoride in physiological condition and in waste water.