Cyclodextrin-based optosensor for the determination of warfarin in waters

Highly Sensitive and Selective Detection of Uranyl Ions Based on a Tb3+-Functionalized MOF via Competitive Host-Guest Coordination

Owing to the rapid development of the nuclear industry, uranium has become a global environmental contaminant due to its radiotoxicity and chemotoxicity, posing significant threats to human health and ecological safety. Although various instrumental and chemical analytical methods have been developed for uranyl ion detection in aquatic environments, searching for new sensors with high stability, sensitivity, and selectivity remains a challenge. In this study, a luminescent Zr-based metal-organic framework (MOF), designated as Tb@UiO-66-(COOH)2, was successfully synthesized utilizing a postsynthetic exchange (PSE) method along with Tb3+ ion doping for uranyl ion detection. Interestingly, the presence of UO22+ ions causes a replacement of guest ions (Tb3+) in the sensor via a competitive host-guest interaction, leading to significant luminescence quenching. The attenuation of the luminescence intensity of Tb@UiO-66-(COOH)2 exhibits an excellent linear relationship with UO22+ ion concentrations within a wide range of 0-2.52 μM. Notably, Tb@UiO-66-(COOH)2 demonstrates an unprecedentedly high detection sensitivity (Ksv = 2.16 × 105 M-1) and an extremely low limit of detection (LOD) down to 8.03 nM (1.91 ppb) in deionized water. More importantly, Tb@UiO-66-(COOH)2 can achieve high selectivity and efficient detection performance, even in the presence of significant excesses of competing ions. The values of Ksv were determined to be 2.10 × 105 M-1 in Xie'ao Lake water and 3.05 × 105 M-1 in seawater; the values of LOD were determined to be 8.26 nM (1.96 ppb) in Xie'ao Lake water and 5.68 nM (1.35 ppb) in seawater. To the best of our knowledge, this is the first instance of introducing a competitive host-guest coordination strategy into a MOF-based chemical sensor to achieve high-performance uranyl ion detection. Hence, the present work offers a novel idea for building functional MOFs for uranyl ion detection in aqueous solutions.

Machine Learning-Assisted Biomass-Derived Carbon Dots as Fluorescent Sensor Array for Discrimination of Warfarin and Its Metabolites

Warfarin (WAR), an effective oral anticoagulant, is of utmost importance in treating many diseases. Despite its significance, rapid and precise discrimination of WAR remains a formidable challenge, especially facing its structural analogs of metabolites. Here, three kinds of herb-derived N-doped carbon dots (NCDs) were greenly synthesized via a fast and simple microwave-assisted method. Three NCDs showcased respectable blue fluorescent (FL) properties and sensing capabilities for the discrimination of WAR and its metabolites. To improve accuracy in identifying WAR and its metabolites, a sensor array composed of three unique herb-derived NCDs was meticulously designed. Combined with the machine learning model, the sensor array displayed a strong immunity to interference in the discrimination of the WAR, even in unknown samples. Meanwhile, the FL sensing mechanism is deeply expounded. The methodology proffers broad prospects for biomass-derived nanomaterials and provides an effective and feasible project for pharmaceutical analysis by capitalizing on machine learning.

An optoelectronic flow-through detectors for active ingredients determination in the pharmaceutical formulations

An optoelectronic flow-through detector for active ingredients determination in pharmaceutical formulations is explained. Two consecutive compact photodetector's devices operating according to light-emitting diodes-solar cells concept where the LEDs acting as a light source and solar cells for measuring the attenuated light of the incident light at 180˚ have been developed. The turbidimetric detector, fabricated of ten light-emitting diodes and five solar cells only, integrated with a glass flow cell has been easily adapted in flow injection analysis manifold system. For active ingredients determination, the developed detector was successfully utilized for the development and validation of an analytical method for warfarin determination in pure and pharmaceutical preparations. The developed method is based on the forming of a white, turbid product as a result of a reaction between the warfarin and semicarbazide which was used as an oxidizing agent. The developed flow-through detector system is semi mechanized, economic in materials consumption, easy to operate and characterized by excellent analytical results. Both developed analytical devices used in two channels flow injection system allow for turbidimetric measurements of warfarin in 0.9-154 μg ml^-1 and 123-1600 μg ml^-1 ranges of concentration, with limits of detections 0.73 μg ml^-1 and 24.66 μg ml^-1 for photodetectors 1& 2 respectively. The turbidity measurement procedure for the current flow system offers to conduct 60 tests per hour of the warfarin which is the most needs of quality control analysis in industrial applications. To ensure the analytical usefulness of the flow system, the warfarin has been analyzed in the real samples with a fully acceptable agreement and a correlation between the results offered by the developed flow system and the official method.

Sensors Applied for the Detection of Pesticides and Heavy Metals in Freshwaters

Water is essential for every life living on the planet. However, we are facing a more serious situation such as water pollution since the industrial revolution. Fortunately, many efforts have been done to alleviate/restore water quality in freshwaters. Numerous sensors have been developed to monitor the dynamic change of water quality for ecological, early warning, and protection reasons. In the present review, we briefly introduced the pollution status of two major pollutants, i.e., pesticides and heavy metals, in freshwaters worldwide. Then, we collected data on the sensors applied to detect the two categories of pollutants in freshwaters. Special focuses were given on the sensitivity of sensors indicated by the limit of detection (LOD), sensor types, and applied waterbodies. Our results showed that most of the sensors can be applied for stream and river water. The average LOD was72.53±12.69 ng/ml (n=180) for all pesticides, which is significantly higher than that for heavy metals (65.36±47.51 ng/ml,n=117). However, the LODs of a considerable part of pesticides and heavy metal sensors were higher than the criterion maximum concentration for aquatic life or the maximum contaminant limit concentration for drinking water. For pesticide sensors, the average LODs did not differ among insecticides (63.83±17.42 ng/ml,n=87), herbicides (98.06±23.39 ng/ml,n=71), and fungicides (24.60±14.41 ng/ml,n=22). The LODs that differed among sensor types with biosensors had the highest sensitivity, while electrochemical optical and biooptical sensors showed the lowest sensitivity. The sensitivity of heavy metal sensors varied among heavy metals and sensor types. Most of the sensors were targeted on lead, cadmium, mercury, and copper using electrochemical methods. These results imply that future development of pesticides and heavy metal sensors should (1) enhance the sensitivity to meet the requirements for the protection of aquatic ecosystems and human health and (2) cover more diverse pesticides and heavy metals especially those toxic pollutants that are widely used and frequently been detected in freshwaters (e.g., glyphosate, fungicides, zinc, chromium, and arsenic).

Sequestration Effect on the Open-Cyclic Switchable Property of Warfarin Induced by Cyclodextrin: Time-Resolved Fluorescence Study

The excited-state lifetimes of the anticoagulant drug warfarin (W) in water and in the absence and presence of methyl-β-cyclodextrins (Me-β-CD) were recorded using time-resolved fluorescence measurements. Selective excitation of the open and cyclic protonated isomers of W were acquired with laser emitting diodes (LED) producing 320 and 280 nm excitation pulses, respectively. Formation of the inclusion complex was checked by UV-visible absorption spectroscopy, and the values of binding constants (2.9 × 10³ M^-1 and 4.2 × 10² M^-1 for protonated and deprotonated forms, respectively) were extracted from the spectrophotometric data. Both absorption and time-resolved fluorescence results established that the interior of the macromolecular host binds preferentially the open protonated form, red shifts the maximum of its absorption of light at ~305 nm, extends its excited-state lifetime, and decreases its emission quantum yield (Ф_F). Collectively, sequestration of the open guest molecules decreases markedly their radiative rate constants (k_r), likely due to formation of hydrogen-bonded complexes in both the ground and excited states. Due to lack of interactions, no change was observed in the excited-state lifetime of the cyclic form in the presence of Me-β-CD. The host also increases the excited-state lifetime and Ф_F of the drug deprotonated form (W^-). These later findings could be attributed to the increased rigidity inside the cavity of Me-β-CD. The pK_a values extracted from the variations of the UV-visible absorption spectra of W versus the pH of aqueous solution showed that the open isomer is more acidic in both ground and excited states. The positive shifts in pK_a values induced by three derivatives of cyclodextrins: HE-β-CD, Ac-β-CD, and Me-β-CD supported the preferential binding of these hosts to open isomers over cyclic.

Complexation study of brilliant cresyl blue with beta-cyclodextrin and its derivatives by UV-vis and fluorospectrometry

The complexation reactions of brilliant cresyl blue (BCB) with beta-cyclodextrin (beta-CD), mono[2-O-(2-hydroxypropyl)]-beta-CD (2-HP-beta-CD), mono[2-O-(2-hydroxyethyl)]-beta-CD (2-HE-beta-CD), and heptakis(2,6-di-methyl) -beta-CD (DM-beta-CD) were investigated using UV-vis and fluorospectrometry. The complexation between BCB and CDs could inhibit the aggregation of BCB molecules and could cause its absorbance at 634nm gradually increasing. The fluorescence of BCB was also enhanced with the addition of CDs. The fluorescence enhancement was more notable in neutral and acidic media than in basic media. Hildebrand-Benesi equation was used to calculate the formation constants of beta-CDs with BCB based on the fluorescence differences in the CDs solution. The stoichiometry ratio was found to be 1:1. The complexing capacities of beta-CD and its three derivatives were compared and the results followed the order: 2-HP-beta-CD>2-HE-beta-CD>DM-beta-CD>beta-CD. The effect of temperature on the formation of BCB-beta-CD inclusion complexes has also been examined. The results revealed that the formation constants decreased with the increase of temperature from 1038.9 to 491.6l/mol. Enthalpy and entropy values were calculated and the values were -25.77kJ/mol and 35.04J/kmol, respectively. The thermodynamic measurements suggest that the inclusive process was enthalpic favor. The release of high-energy water molecules and Van der Waals force played an important role in the inclusive process.

Environmental analysis based on luminescence in organized supramolecular systems

The use of organized supramolecular systems-including micellar media and cyclodextrin inclusion complexes-combined with luminescence techniques in the study and determination of compounds and elements of environmental interest from 1990 to 2005 is reviewed. Analyses of environmental samples performed using fluorescence, photochemically induced fluorescence and phosphorescence spectroscopy as well as liquid chromatography, capillary electrophoresis and flow injection with luminescence detection in the presence of these organized media are described in detail.