Carbon dots-inspired fluorescent cyclodextrins: competitive supramolecular “off–on” (bio)sensors

Abstract

Chromophore-appended cyclodextrins combine the supramolecular loading capabilities of cyclodextrins (CDs) with the optical properties of the affixed chromophores. Among fluorescent materials, carbon dots (CNDs) are attractive and the feasibility of CND-appended CDs as sensors has been demonstrated by different authors. However, CNDs are intrinsically heterogeneous materials and their ulterior functionalization yields hybrid composites that are not well defined in terms of structure and composition. Inspired by the fluorescence properties of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA), the most paradigmatic of the molecular fluorophores detected in CNDs, herein we report two highly efficient synthetic chemical strategies for the preparation of IPCA-appended CDs that behave as CND-based CD "turn off-on" biosensors suitable for the analysis of cholesterol and β-galactosidase activity. We have deconstructed the CND-CD systems to demonstrate that (i) the role of CNDs is limited to acting as a support for the molecular fluorophores produced during their synthesis and (ii) the molecular fluorophores suffice for the determination of the enzymatic activity based on the quenching by p-nitrophenol as a sacrificial quencher. † Electronic supplementary information (ESI) available: Spectroscopic characterization of new compounds, and ESI schemes, figures, and tables. See

Portable Instrument for Hemoglobin Determination Using Room-Temperature Phosphorescent Carbon Dots

“…In general, the formation of CDs doped with N mainly involves two processes: condensation and carbonization. During these processes, the carboxyl and hydroxyl groups of citric acid and the amino groups of ethylenediamine undergo complex condensation and carbonization reactions involving intramolecular condensation to form small-molecule fluorophores, such us 5-oxo-1,2,3,5-tetrahydroimidazo[1,2a]pyridine-7-carboxylic acid [ 29 ] as well as carbon core-containing nitrogen-doped carbon dots. The resulting molecular fluorophores are hypothesized to be located on the surface and/or inside the CDs.…”

Mono-6-Substituted Cyclodextrins—Synthesis and Applications

“…The product was then precipitated from EtOH, further purified by ion-exchange column chromatography, and obtained in a 39% yield. De los Reyes-Berbel et al [ 199 ] developed a synthesis of a complex γ-CD derivative that behaves like a ”turn off-on” biosensor. The initial γ-CD intermediate was prepared from Ts-γ-CD with ethanolamine (20 eq.)…”

“…The yield was 12%. De los Reyes-Berbel et al [ 199 ], mentioned at secondary amino γ-CDs, performed Michael addition of prepared ethanolamine-derived γ-CDs with divinyl sulfone (2 eq.) in water at rt.…”