Selective sensing of PPi by fluorogenic Al(III)-probe complex in aqueous medium

Area of Science:

• Chemical Sensing
• Fluorescence Spectroscopy
• Analytical Chemistry

Background:

• Schiff bases are versatile ligands with applications in coordination chemistry and sensing.
• Aluminum ions (Al³⁺) play crucial roles in biological processes but their dysregulation is linked to diseases.
• Pyrophosphate (PPi) is an important biological metabolite involved in various cellular functions.

Purpose of the Study:

• To design and synthesize a novel Schiff base probe (JN) for the selective detection of Al³⁺.
• To investigate the sensing mechanism of JN towards Al³⁺ and its subsequent detection of pyrophosphate (PPi).
• To evaluate the practical applicability of the probe and its complex in biological samples.

Main Methods:

• Synthesis of Schiff base probe JN.
• Spectroscopic studies (fluorescence, UV-Vis) to analyze sensing mechanisms.
• Theoretical calculations to support proposed mechanisms (PET, ICT, ESIPT, CHEF).
• High-resolution mass spectrometry (HRMS) to study ion binding.
• Fluorescence imaging in zebrafish and onion epidermal cells.

Main Results:

• JN exhibited a "turn-on" fluorescence response selective for Al³⁺ in aqueous media.
• The sensing mechanism involved a combination of PET, ICT, ESIPT, and CHEF processes.
• The JN-Al³⁺ complex could sequentially detect PPi ions via a "turn-off" fluorescence response.
• HRMS revealed that Al³⁺ can bind with 1, 2, or 3 PPi ions.
• Successful fluorescence imaging of Al³⁺ and PPi in biological samples.

Conclusions:

• The developed Schiff base probe JN is a highly sensitive and selective chemosensor for Al³⁺.
• The probe facilitates sequential detection of PPi ions after Al³⁺ binding.
• The probe and its complex show potential for in situ monitoring of Al³⁺ and PPi in biological systems.