Highly selective fluorescent turn-on-off sensing of OH-, Al3+ and Fe3+ ions by tuning ESIPT in metal organic frameworks and mitochondria targeted bio-imaging

Herein we report a multifunctional high performance metal organic framework (Zn-DHNDC MOF) based chemosensor that displays an exceptional excited state intramolecular proton transfer (ESIPT) tuned fluorescence turn-on-off response for OH-, Al3+ and Fe3+ ions along with mitochondria targeted bio-imaging. Properly tuning ESIPT as well as the hydroxyl group (-OH) allows Zn-DHNDC MOF to optimize and establish chelation enhanced fluorescence (CHEF) and chelation enhanced quenching (CHEQ) based sensing mechanisms. The MOF benefits from acid-base interactions with the ions which generate a turn-on bluish green fluorescence (lambda(Em) 492 nm) for OH-, an intense turn-on green fluorescence (lambda(Em) 528 nm) for Al3+ and a turn-off fluorescence quenching response for Fe3+ ions. The aromatic -OH group indeed plays its part in triggering CHEF and CHEQ processes responsible for the turn-on-off events. Low limits of detection (48 nM of OH-, 95 nM for Al3+, 33 nM for Fe3+ ions), high recyclability and fast response time (8 seconds) further assist the MOF to implement an accurate quantitative sensing strategy for OH-, Al3+ and Fe3+ ions. The study further demonstrates the MOF's behaviour in cellular medium by subjecting it to live cell confocal microscopy. Along with a bio-compatible nature the MOF exhibited successful accumulation inside the mitochondria of MCF7 cancer cells, which defines it as a significant bio-marker. Therefore the present work successfully represents the multidisciplinary nature of Zn-DHNDC MOFs, primarily in sensing and biomedical studies.

Automated summary

This study presents a multifunctional high performance metal organic framework chemosensor with exceptional fluorescence response for OH-, Al3+, and Fe3+ ions, as well as targeted bio-imaging in mitochondria. By optimizing ESIPT and hydroxyl group interactions, the MOF demonstrates chelation enhanced fluorescence and quenching mechanisms for accurate quantitative sensing in cellular medium. The MOF's successful accumulation inside MCF7 cancer cell mitochondria highlights its potential as a significant biomarker, showcasing its value in sensing and biomedical applications.