Ratiometric Fluorescence Chiral Sensors for pH Monitoring and Its Applications in Indicator Paper and Bioimaging.

Area of Science:

• Nanomaterials Science
• Chemical Biology
• Quantum Chemistry

Background:

• Chirality is fundamental in biological systems, and chiral nanomaterials are a rapidly growing research area.
• Comparing the pH response of enantiomers is a significant challenge in chemistry.
• Silicon quantum dots (SiQDs) offer potential for sensitive and accurate ratiometric sensing methods.

Purpose of the Study:

• To develop chiral Cdots (carbon dots) with distinct pH sensitivities for enantiomer comparison.
• To utilize modified SiQDs for a sensitive and accurate ratiometric pH sensing method.
• To investigate the pH response mechanism of chiral probes based on aggregation caused quenching (ACQ).

Main Methods:

• Preparation of chiral d/l-Cdots by post-modifying an achiral Cdots core with arginine enantiomers.
• Employment of modified SiQDs for a ratiometric fluorescence sensing approach.
• Utilizing quantum mechanical (QM) calculations to validate experimental findings.

Main Results:

• Chiral d- and l-Cdots probes demonstrated different pH sensitivities with distinct linear ranges (d-probes: pH 4.0-8.0; l-probes: pH 3.5-7.5).
• The fluorescence response followed an 'on-off' strategy governed by ACQ in response to pH changes.
• QM calculations confirmed stronger binding affinity and aggregation of d-Cdots in acidic conditions compared to l-Cdots.

Conclusions:

• The developed chiral probes offer a novel approach for comparing enantiomer pH sensitivities.
• These probes were successfully applied as indicator paper for accurate intracellular pH (pHi) detection in SK-BR-3 breast cancer cells.