Fluorescent Sensor Array for Quantitative Determination of Saccharides.

Accurate monitoring of sugar levels is essential for many fields from food industry to human health. Here, we developed FRET-based dual chromophore sensors for saccharides that form oxazolidine boronate and may be employed as a noninvasive method for monitoring of sugar levels in biological fluids, namely, urine. The saccharide-binding properties of the sensors were studied using fluorescence spectroscopy and utilized in the determination of saccharides in a high-throughput manner. Here, two fluorescent sensors were successful in the classification of nine different monosaccharides and disaccharides with 100% correct classification. Furthermore, the dual chromophore self-assembled sensors were successfully utilized for the quantitative determination of important carbohydrates such as glucose in the presence of competitive saccharides (fructose) and in complex media (urine) without sample pretreatment. The present fluorescent sensors allow for quantification of glucose in a concentration range of 0-60 mM, which matches the concentration range of frequently used urinalysis test strips.

A Fluorescence Sensor Array Based on Zinc(II)-Carboxyamidoquinolines: Toward Quantitative Detection of ATP*.

The newly prepared fluorescent carboxyamidoquinolines (1-3) and their Zn(II) complexes (Zn@1-Zn@3) were used to bind and sense various phosphate anions utilizing a relay mechanism, in which the Zn(II) ion migrates from the Zn@1-Zn@3 complexes to the phosphate, namely adenosine 5'-triphosphate (ATP) and pyrophosphate (PPi), a process accompanied by a dramatic change in fluorescence. Zn@1-Zn@3 assemblies interact with adenine nucleotide phosphates while displaying an analyte-specific response. This process was investigated using UV-vis, fluorescence, and NMR spectroscopy. It is shown that the different binding selectivity and the corresponding fluorescence response enable differentiation of adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), pyrophosphate (PPi), and phosphate (Pi). The cross-reactive nature of the carboxyamidoquinolines-Zn(II) sensors in conjunction with linear discriminant analysis (LDA) was utilized in a simple fluorescence chemosensor array that allows for the identification of ATP, ADP, PPi, and Pi from 8 other anions including adenosine 5'-monophosphate (AMP) with 100 % correct classification. Furthermore, the support vector machine algorithm, a machine learning method, allowed for highly accurate quantitation of ATP in the range of 5-100 µM concentration in unknown samples with error <2.5 %.

Exploiting fluorescent zinc(ii) and copper(ii) complexes for enantiomeric excess determination of hydroxycarboxylates.

Chiral hydroxycarboxylates are useful compounds in the syntheses of natural products, pharmaceutical intermediates, and drugs. Here, we report on Zn- and Cu-containing sensors that can distinguish between enantiomers of hydroxycarboxylates through the quenching or the enhancement of fluorescence. A Zn-based sensor-[ZnRRL]2+-is used in an assay to perform analyses of enantiomeric excess (% ee) of scalemic mixtures of α-hydroxycarboxylates and various drugs including the statin drug atorvastatin. This assay enables determination of mixtures of enantiomers across the range from 0 to 100% ee.

A dual chromophore sensor for the detection of amines, diols, hydroxy acids, and amino alcohols.

The determination of enantiomeric excess (ee) in various groups of chiral compounds, namely amines, amino alcohols, diols, and hydroxy acids is performed using a dual chromophore FRET/PET based sensor ensemble. The sensing ensemble utilizes fluorescence changes from two chromophores (indicators) to classify 13 pairs of enantiomers as well as allows for the qualitative and quantitative determination of ee of various classes of chiral compounds with high accuracy (<2% error).

Anion Sensing by Fluorescent Expanded Calixpyrroles.

Expanded calixpyrrole-type macrocycles, calix[2]benzo[4]pyrroles, bearing fluorescent moieties attached via conjugated vinyl spacers, have been synthesized from the corresponding formyl derivatives through Knoevenagel condensation. The anion-binding properties of the resulting fluorescent macrocycles have been studied by means of NMR, UV/Vis, and fluorescence spectroscopies. Our main focus has been on dicarboxylates matching the size of the binding cavity of the calix[2]benzo[4]pyrrole skeleton. The observed anion-binding properties were compared with those of the regular calix[4]pyrroles bearing identical fluorophores. Surprisingly, the parent calix[4]pyrroles appear to be equally efficient, if not more so, for sensing anions such as dicarboxylates. Affinity constants determined for various anions and dianions show the sensors S1-S5 to be highly cross-reactive. The cross-reactivity of the sensors was utilized in a microchip-based array, which showed perfect (100 %) classification of 18 analytes utilizing only five sensors. Finally, the same array was used to quantitatively analyze dicarboxylates such as oxalate and malonate. The data from the array were subjected to linear regression, allowing the determination of various concentrations of dianions with low error (<2 %).

Biguanides, anion receptors and sensors.

Biguanides are strong bases (pKa > 10), their protonated forms bind anions and may therefore act as receptors for anions. We report on easy-to-make anion receptors and fluorescence-based sensors utilizing the biguanide moieties that respond to the presence of anions with a change in fluorescence. The observed changes in fluorescence are anion-specific and even though the biguanide receptors are cross-reactive, these sensors may be used to identify various anions (halides, carboxylates, phosphates). Paper-based analytical arrays were used to assess the discriminatory ability of the sensors in the qualitative and quantitative analysis of multiple anions.

Supramolecular Sensors for Opiates and Their Metabolites.

The present study highlights a sensing approach for opiates using acyclic cucurbituril (aCBs) sensors comprising four glycouril units terminated on both ends with naphthalene fluorophore walls. The connectivity between the glycourils and naphthalene rings largely defines the opening size of the cucurbituril cavity and its diameter. The large hydrophobic binding cavity is flexible and is able to adapt to guests of various size and topology. The recognition event between the aCBs and guests results in modification of the fluorescence of the terminal walls, a fluorescence response that can be used to sense the drugs of abuse morphine, heroin, and oxycodone as well as their metabolites. Molecular dynamics is employed to understand the nature of the binding interactions. A simple three sensor cross-reactive array enables the determination of drugs and their metabolites in water with high fidelity and low error. Quantitative experiments performed in urine using a new three-way calibration model allows for determination of drugs and their metabolites using one sensor from a single fluorescence reading.