Carboxylato-pillar[6]arene-based fluorescent indicator displacement assays for the recognition of monoamine neurotransmitters.

Adrien Paudics,Miklós Kubinyi,Márton Bojtár,István Bitter

doi:10.1039/c9ra03241j

Abstract

The complexation of three cationic fluorescent dye guests with the anionic host carboxylato-pillar[6]arene (WP6) was investigated by optical and NMR spectroscopy. Among the selected indicators – a stilbazolium dye (i1) and two naphthalimide derivatives with positively charged ‘anchor’ groups (i2 and i3) – i1 gave a large turn-on, i2 and i3 a large turn-off fluorescence response to the complexation. The size selectivity of the complex formation of pillararenes was demonstrated by comparing the binding constants of the complexes of the three indicators with WP6 and its smaller homologue, WP5. The systems WP6·i1 and WP6·i2 were tested as indicator displacement assays for the sensing of monoamine neurotransmitters. The WP6·i1 system functioned as a turn-off, the WP6·i2 system as a turn-on sensor for neurotransmitters, and both assays showed a good selectivity to histamine over the other neurotransmitter analytes.

Highlights

Arti cial receptor molecules operating through host–guest interactions capable of selective molecular recognition can be applied in supramolecular analytical systems to detect and quantify the analytes of interest.[4,5,6]
The complexation caused a signi cant redshi in the absorption maximum and an intense uorescence enhancement. These changes can be explained in terms of the existence of an emissive directly excited charge transfer (CT) state and a dark twisted intramolecular charge transfer (TICT) state on the S1 potential energy surface of i1
The dipole moment is signi cantly higher in the S1(CT) state than in the ground state, the S1(CT) state molecule is stabilised in the environment of the high negative charge density of the with the anionic host carboxylato-pillar[6]arene (WP6) host, leading to the redshi of the absorption band

Summary

Introduction

Since the emergence of supramolecular chemistry, the recognition of molecules with biological interest is a topic of great importance.[1,2,3] Arti cial receptor molecules operating through host–guest interactions capable of selective molecular recognition can be applied in supramolecular analytical systems to detect and quantify the analytes of interest.[4,5,6] Macrocycles, due to their inherent structural nature are ideal hosts for various biomolecules, attaching a signaling group to the water soluble derivatives is highly challenging.[7]. Both the systems WP6$i1 and WP6$i2 worked as FID assays for neurotransmitters, showing selectivity towards histamine over the other analytes (Fig. 2).

Results

Conclusion