Cyclodextrin Supramolecular Complex as a Water-Soluble Ratiometric Sensor for Ferric Ion Sensing

Abstract

Heightened concern for human health and environmental protection has stimulated active research on the potential impact of transition-metal ions and their toxic effects, thus it is very demanding to design transition-metal ion detection methods that are cost-effective, rapid, facile, and applicable to the environmental and biological milieus. In this study, we demonstrated an alternative strategy for constructing a water-soluble FRET-based ratiometric sensor for ferric ion detection by forming a supramolecular beta-cyclodextrin/dye complex. This water-soluble FRET system consists of a dansyl-linked beta-cyclodextrin (beta-CD-DNS) and a spirolactam rhodamine-linked adamantane (AD-SRhB). The dansyl moiety serves as the donor, and the spirolactam-rhodamine B derivative (SRhB) was chosen as a sensitive, selective chemosensor for Fe(III) ions and a very efficient ring-opening reaction induced by Fe(III) generates the long-wavelength rhodamine B fluorophore that can act as the energy acceptor. Moreover, the adamantyl (AD) group, which is known for its capability to form stable host-guest inclusion complexes with beta-CD derivatives, was covalently linked to the spirolactam rhodamine, thus the adamantyl moiety of the ion-recognition element can be anchored inside the CD cavity. In this way, the donor-acceptor separation can be kept within the critical Forster distance; accordingly, energy transfer can take place from the donor (dansyl) to the acceptor (rhodamine derivative/Fe(III) complex), and thus ratiometric detection for Fe(III) in an aqueous medium can be fulfilled. This FRET-based supramolecular sensor can be readily formed via an inclusion process using the donor part and the acceptor part, hence this strategy could afford a robust approach for constructing a wide range of FRET-based water-soluble sensing systems simply by assembling a specifically predesigned donor-linked CD and acceptor-linked adamantane.

Organic‐Inorganic Molecular Nano‐Sensors: A Bis‐Dansylated Tweezer‐Like Fluoroionophore Integrating a Polyoxometalate Core

“…The dansyl label carries some key optical properties, such as: (i) intense fluorescence in the visible region; (ii) relatively long emission wavelength; (iii) a high Stokes shift behavior preventing self quenching; (iii) solvatochromism, by effect of a twisted intramolecular charge-transfer (TICT) excited state, and (iv) selective excitation/absorption response of the protonated state, leading to antenna-effects in polydansylated arrays. [16,17] These unique features have been successfully exploited for the molecular design of fluorescent chemosensors in which the dansyl chromophore is used in combination with receptor domains, including multi-dentate ligands, [18] supramolecular hosts such as calix [4]arenes, [19] cyclodextrins, [20] crown ethers, [21] and also nano-silica surfaces. [22] Depending on the dansyl environment, selective fluoroionophores have been obtained with interesting sensitivity towards ions such as Pb 2+ , [23] Hg 2+ , [18,24] and Cu 2+ .…”

Host–guest-recognition-based polymer brush-functionalized mesoporous silica nanoparticles loaded with conjugated polymers: A facile FRET-based ratiometric probe for Hg 2+

“…However, after forming the inclusion of adamantine in a β-CD cavity for PPV@MSN@PGMA@CD@ AD-SRhB after host-guest interactions, the probe can detect Hg 2+ from other interfering ions effectively. It has been reported that the metal ions such as Fe 3+ , Al 3+ and Hg 2+ can all induce ring-opening AD-SRhB [37][38][39] before the recognition between β-CD and AD-SRhB. In our work, Fe 3+ and Al 3+ hardly induce ring-opening AD-SRhB for the probe of PPV@MSN@PGMA@CD@ AD-SRhB after the host-guest recognition possibly due to the other stronger adsorption sites for Fe 3+ and Al 3+ presented in PPV@MSN@PGMA@CD nanoparticles.…”

Conjugated polymer and spirolactam rhodamine-B derivative co-functionalized mesoporous silica nanoparticles as the scaffold for the FRET-based ratiometric sensing of mercury (II) ions

“…Ratiometric fluorescence sensing technology, which uses the ratio of two fluorescent peaks instead of the absolute fluorescence intensity of one peak, has gained much attention in recent years [9]. The advantage of the ratiometric sensors is that some factors such as excitation source fluctuations and sensor concentration will not affect the ratio between the two fluorescence intensities [10,11]. In particular, the ratiometric fluorescent sensors can eliminate most ambiguities in the Hg 2þ ion detection by self-calibration of two emission bands [12,13].…”