A Copper(II) Macrocycle Complex for Sensing Biologically Relevant Organic Anions in a Competitive Fluorescence Assay:...

Area of Science:

• Analytical Chemistry
• Chemical Sensing
• Biomedical Sensing

Background:

• Oxalate sensing is crucial due to its societal impact.
• Previous oxalate sensors were assumed selective, but tested against limited analytes.
• Biological samples contain interfering anions like citrate and urate.

Purpose of the Study:

• To reassess the selectivity of a dinuclear copper(II) macrocycle (Cu2L) for oxalate sensing.
• To evaluate Cu2L's response to biologically relevant anions using an eosin Y displacement assay.
• To determine if Cu2L is suitable for oxalate detection in complex biological matrices.

Main Methods:

• Eosin Y displacement assay to measure fluorescence response.
• Testing Cu2L selectivity against a panel of biologically relevant anions.
• Single-crystal X-ray crystallography to elucidate binding interactions.

Main Results:

• Cu2L showed significant indicator displacement with urate, oxaloacetate, and citrate, not just oxalate.
• Larger anions (urate, oxaloacetate, citrate) induced a response, contrary to expectations.
• X-ray crystallography suggested non-selective binding due to accessible copper ions and potential π-π stacking.

Conclusions:

• The dinuclear copper(II) macrocycle (Cu2L) is not selective for oxalate in biological samples.
• Interfering anions like urate, oxaloacetate, and citrate cause false positives.
• Cu2L requires sample pre-treatment to remove interfering compounds for accurate oxalate sensing.