Cyclodextrin sensors

Lungu NC, Depret A, Delattre F, Surpateanu GG, Cazier F, Woisel P, ShiraU P, Surpateanu G (2005) Synthesis of a new fluorinated fluorescent p-cyclodextrin sensor. J Fluor Chem 3 385-388... 

In a similar fashion, steroids are molecules that have been investigated by disruption of FRET. The sensor is a double labeled peptide with cyclodextrin bound to one side chain. The latter keeps the fluorophores closely together by accommodating the coumarin into its cavity thereby ensuring efficient FRET. Steroids compete for the cavity of cyclodextrin and displace the coumarin reducing FRET efficiency. This model, although useful for in vitro applications, seems to be poorly selective for its application in biological samples [95],... 

K. Hamasaki, H. Ikeda, A. Nakamura, A. Ueno, F. Toda, I. Suzuki, andT. Osa, Fluorescence sensors of molecular recognition. Modified cyclodextrins capable of exhibiting guest-responsive twisted intramolecular charge transfer fluorescence, /. Am. Chem. Soc. 775,5035-5040(1993). 

A prospective sensor made of a couple 159 consisting of p-cyclodextrin 11 and calix[4]arene 18 bearing a fluorophoric substituent was reported by Bugler and coworkers [68]. The compound forms fibers which change into vesicles upon complexation, forcing the fluorophore out of the cyclodextrin cavity. As a consequence, the intensity of fluorescence is reduced. In another approach to... 

This principle is applied for the potential development in the EPMEs and for obtaining the intensity of the current in amperometric immuno-sensors. For the enantioselective, potentiometric electrodes, it is necessary to find a molecule with a special architecture that can accommodate the enantiomer. In this regard, cyclodextrins and their derivatives, maltodextrins, antibiotics and fullerenes and their derivatives were proposed [17-52]. 

The main components of the membrane of the enantioselective, potentiometric electrode are chiral selector and matrix. Selection of the chiral selector may be done accordingly with the stability of the complex formed between the enantiomer and chiral selector on certain medium conditions, e.g., when a certain matrix is used or at a certain pH. Accordingly, a combined multivariate regression and neural networks are proposed for the selection of the best chiral selector for the determination of an enantiomer [17]. The most utilized chiral selectors for EPME construction include crown ethers [18-21], cyclodextrins [22-35], maltodextrins 136-421, antibiotics [43-50] and fullerenes [51,52], The response characteristics of these sensors as well as their enantioselectivity are correlated with the type of matrix used for sensors construction. 

S-enalapril assay can be done using the potentiometric electrode based on impregnation of 2-hydroxy-3-trimethylammoniopropyl-/i-cyclodextrin (as chloride salt) solution in a carbon paste, in the 3.6 x 10 5-6.4 x 10-2 mol/L (pH between 3.0 and 6.0) concentration range with a detection limit of 1.0 x 10 5 mol/L [25]. The slope is near-Nernstian 55.00 mV/decade of concentration. The average recovery of S-enalapril raw material is 99.96% (RSD — 0.098%). The potentiometric selectivity coefficient over D-proline (6.5 x 10 4) proved the sensor s enantioselectivity. S-enalapril was determined from pharmaceutical tablets with an average recovery of 99.59% (RSD — 0.20%). 

The EPME based on impregnation of 2-hydroxy-3-trimethylammoniop-ropyl-//-cyclodextrin (as chloride salt) solution in a carbon paste can be reliably used for S-trandolapril assay with an average recovery of 99.77% (RSD — 0.22%) [24]. The linear concentration range is 10 4-10 2 mol/L on the 2.5-5.5 pH range. The detection limit is of 10 5 mol/L magnitude order. The slope is near-Nernstian 52.45 mV/decade. The sensor enantioselectivity was determined over D-proline, when a 10 4 magnitude order was obtained for potentiometric selectivity coefficient. 

Chapter 8, by Ueno and Ikeda, focuses on the photophysics and photochemistry of organic molecules within cyclodextrins. Particular emphasis is placed on the use of modified cyclodextrins as sensors for neutral organic molecules. In this context readers are referred to Volume 7 of the series, which is devoted to sensors and switches. 

Cyclodextrins can be used as fluorescence sensors or as hosts for direct optical detection with methods like SPR. 

For the application of label-free optical transduction principles like SPR or RIfS, a chiral receptor bound to a transparent polymer layer is required. As various types of these polymers have already been applied to chromatographic separation processes, a substantial wealth of knowledge was achieved during the last few decades. Stationary materials like bonded amide selectors or cyclodextrins were adopted as sensor coatings. Several different applications of these materials in various fields of interest have been reported in the literature [17]. 

All sensors of the array were exposed simultaneously to the test gases. Dry air was used as a carrier gas. In Fig. 9 the sensor responses of Iipodex E to both enantiomers of halodiether B in a concentration range from 0 to 140 xgl-1 is shown. The interaction between the cyclodextrin-recognition units and the S-enantiomer is stronger than that with the R-enantiomer. 

Cyclodextrins (Sect. 2.2), have the ability to include various organic molecules in their central cavities. Chromophores have been finked to cyclodextrins to build spectroscopic sensors for organic molecules. Many fluorescent cyclodextrins have been prepared to be used as molecular sensors in solution. 

Dansylglycine-modified cyclodextrin (DnsC4-/i-CD) was found to be capable of being immobilised on a cellulose membrane and of acting as a fluorescence sensor for enantiomers [36]. DnsC4-/J-CD decreased its fluorescence intensity upon exposure to guest molecules. This result implicates a useful application of a cellulose membrane as a supporting material for various... 

Fukushima, M. Osa, T. and Ueno, A. (1991) Photoswitchable Multi-response Sensor of Azobenzene-modified y-Cyclodextrin for Detecting Organic Compounds, Chem. Lett. 709-712. 

Ueno, A. (1993) Modified cyclodextrin as supramolecular sensors of molecular recognition, New Funct. Mater. C. 521-526. 

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