Stimuli-responsive and biocompatible pyridyhydrazone-phenol Schiff base and its Zn(II)-complex: Distinct fluorescent detection of SO42-/CO32- in cell lines and real water samples.

BACKGROUND

Widely studied organic photochromic and thermochromic materials exhibit potential application in numerous fields i.e. data storage, photo-patterning and molecular switches etc. Although, these stimuli-responsive behavior of ligand and metal complex have been separately studied but their comparative properties have not been well explored till now. Development of chemosensors for highly sensitive, uninterrupted detection of SO42- and CO32- with distinct signaling via sensitive fluorescence technology is of great demand especially in real samples and biological environment.

RESULTS

Present research work focuses on comparative photo/thermo-sensitivity, biological activity along with fluorescent detection and imaging ability of a pyridyhydrazin-salen based Schiff base (1) and its Zn(II)-complex (2). Remarkably, 1 and 2 exhibit rapid photochromism whereas, thermochromic property is demonstrated by 1 only. Both 1 and 2 serve as highly selective and sensitive fluorescent probes for SO42- and CO32- in mixed aqueous-ethanol media via 'turn-on' and 'turn-off' signaling, respectively, which remain unaffected in the background presence of various competing anions. Compound 1 and 2 bind with SO42-/CO32- in 2:1 (probe: anion) and 1:1 stoichiometry, respectively. Cytotoxicity evaluation against macrophage cells demonstrated IC50 value of 180 μg/mL for 1 and an IC50 value of approximately 105 μg/mL for 2. Both compounds exhibited good biocompatibility, and notably, also displayed the ability to sense carbonate and sulfate ions within biologically active macrophage cells.

SIGNIFICANCE: Comparative stimuli-responsive properties of 1 and 2 have been thoroughly which led us with better insights into plausible mechanism with respect to erstwhile reports. Both compounds 1 and 2 exhibited good biocompatibility in macrophage RAW 264.7 cells. Further, 1 and 2 have been successfully used as fluorescent probes for practical detection of SO42- and CO32- in real water samples and in RAW 264.7 cell lines.