Fluorescence switchable sensor enabled by a calix[4]arene-Cu(II) complex system for selective determination of itraconazole in human serum and aqueous solution.

A switchable fluorescence sensor based on a calix (Monapathi et al., 2021) [4]arene:Cu2+ complex (FLCX/Cu) has been developed for the detection of itraconazole (ITZ) with high sensitivity and specificity. For the development of the sensor, the selective complexation of a fluorescent calix (Monapathi et al., 2021) [4]arene derivative (FL-CX) with the Cu2+ ion causing fluorescence quenching was utilized. In addition, the sensor properties of the FLCX/Cu prepared were investigated. For this purpose, various substances (selected anions, cations, and drugs) with which ITZ can be found together were studied in an aqueous solution. Limit of detection (LOD) and limit of quantification (LOQ) values were determined in the range of 1.00-60.0 µg/L as 3.34 µg/L and 11.1 µg/L for ITZ, respectively. Moreover, the real sample analyses were performed in human serum and tablet form. Furthermore, the effect of some possible serum contents on sensor performance was also studied. All these studies confirmed the development of a simple, precise, accurate, reproducible, highly sensitive, and very stable fluorescence sensor.

Nano-scale selective and sensitive optical sensor for metronidazole based on fluorescence quenching: 1H-Phenanthro[9,10-d]imidazolyl-calix[4]arene fluorescent probe.

It is crucial to determine and control the metronidazole (MET) ingredient in food and pharmaceuticals for human health and food safety. Even though many sensors have been previously reported to detect MET, there is still a need for a highly selective and sensitive, easy, fast, cost-effective sensor in this area. Herein, we report a fluorescent calix[4]arene derivative (PIMC) for highly selective and sensitive and facile and rapid MET detection based on fluorescence (FL) quenching. The highest FL quenching occurs when PIMC is exposed to MET solution at 400 nm (λex = 340). Owing to the quenching efficacy of MET linearly up to 5.5 × 104 nM was obtained a detection limit of 2.44 nM. Besides, interferences of other pharmaceuticals and ions on probe performance were investigated. The FL probe was successful in MET detection without the assistance of any separation techniques in a pharmaceutical sample (tablet) with an acceptable recovery of 101.3%. The applicability of the current probe as a paper-based sensor to MET detection has been successfully tested. As a result, the proposed probe presents a fast and suitable strategy to sensitive and selective detect MET and proves a good potential for practical applications, especially pharmaceutical preparations.

Rapid and real-time detection of arginine enantiomers by QCM sensor having a Calix[4]arene receptor bearing asymmetric centers.

This paper describes the sensing studies of a chiral calix[4]arene receptor (5) having (R)-2-phenylglycinol moiety for arginine enantiomers (D-/L-arginine) by using Quartz Crystal Microbalance (QCM) technique. The initial experiments have revealed that the chiral calix[4]arene 5 coated QCM (CCC-QCM) sensor showed good sensing for arginine enantiomers, such that it has exhibited higher sensing towards D-arginine than that of L-arginine. It has been determined that the sensitivity, limit of detection values of CCC-QCM sensor for the D-/L-arginine solutions as 0.024/0.023 Hz/µM and 0.38/1.29 µM, respectively. On the other hand, the racemic mixture studies were optimized using the response surface methodology with central composite design. Consequently, it has been demonstrated that the QCM sensor modification with a calix[4]arene receptor bearing asymmetric centers provided rapid, real-time, sensitive and effective sensing of arginine enantiomers.

Fast and Reversible "Turn on" Fluorescent Sensors Based on Bisphenol-a for Zn2+ in Aqueous Solution.

Two novel bisphenol-A derivatives (R1 and R2) linked pyrene and napthylthiazole moieties were synthesized via condensation reaction, and positively applied for the selective recognition of Zn2+ ion in EtOH/H2O. Their optical properties were observed by using UV-vis and fluorescence measurements. R1 and R2 exhibited high selectivity and sensitivity towards Zn2+ over other metal ions. This fluorescence selectivity may be owing to inhibited excited-state intramolecular proton transfer (ESIPT) and photoinduced electron transfer (PET). The fluorescence titration analysis indicated detection limits of R1 and R2 for Zn2+ at 17.5 nM and 0.94 µM, respectively. Moreover, R1 and R2 were successfully applied to the detection of Zn2+ with different concentrations in water samples.

A phenyl glycinol appended calix[4]arene film for chiral detection of ascorbic acid on gold surface.

This paper describes the synthesis of new chiral calix [4]arene derivative having (R)-2-phenylglycinol moiety (compound 6), and its chiral recognition studies for ascorbic acid (AA) enantiomers by using Quartz Crystal Microbalance (QCM). Initial experiments indicated that the outstanding selective chiral recognition (α) was observed as 2.61 for l-enantiomer of AA. The sensitivity (S) and the limit of detection (LOD) values for L-AA were calculated as 0.0226 Hz/µM and 0.63 µM, respectively. Furthermore, the sorption behavior and mechanism of AA onto compound 6 film were evaluated and the sorption data exhibited a good correlation with the Freundlich isotherm models. The maximum uptake of L-AA by the sensor was found as 5895.76 mg/g. In conclusion, chiral recognition of AA enantiomers as real-time, sensitive, selective and effective was performed by a calixarene derivative coated QCM sensor.

Selective chiral recognition of alanine enantiomers by chiral calix[4]arene coated quartz crystal microbalance sensors.

We describe the synthesis of new chiral calix[4]arene derivatives having (R)-1-phenylethylamine, (S)-1-phenylethylamine, (R)-2-phenylglycinol, and (S)-2-phenylglycinol moieties, and chiral recognition studies for enantiomers of some selected α-amino acid derivatives such as alanine, phenylalanine, serine, and tryptophan using a quartz crystal microbalance (QCM). Initial experiments indicated that the highest selective chiral recognition factor was 1.42 for alanine enantiomers. The sensitivity, limit of detection, and time constant for L-alanine were calculated as 0.028 Hz/µM, 60.9 µM, and 36.2 s, respectively. The results indicated that real-time, sensitive, selective, and effective chiral recognition of alanine enantiomers was achieved with a QCM sensor coated with a chiral calix[4]arene derivative having (R)-2-phenylglycinol moieties.

Selective and Sensitive Fluorescein-Benzothiazole Based Fluorescent Sensor for Zn2+ Ion in Aqueous Media.

An efficient fluorescent sensor based on fluorescein-benzothiazole (FB) for Zn2+ ion was synthesized and characterized systematically. FB exhibited selective and sensitive recognition toward Zn2+ in MeCN-H2O (v/v = 2/1) over other cations due to the spirolactam ring-opening power of Zn2+. The complexation property of FB with Zn2+ ion was examined by 1H NMR, 13C NMR and FTIR experiments. The stoichiometric ratio of the FB-Zn2+ complex was determined from a Job plot to be 1:1. The binding constant (K a) of Zn2+ binding to FB was found to be 4.22 × 104 M- 1, with a detection limit of 5.64 µM. In addition, the practical utility of FB was explored in the form of test strips. Graphical Abstract.

4-tert-butylcalix[4]arene having nitrile pendant groups as Hg²âº selective receptors.

We synthesized a series of 4-tert-butylcalix[4]arene nitriles (5-7) by the reaction of 4-tert-butylcalix[4]arene (1) with 4'-(6-bromohexyloxy)biphenyl-4-carbonitrile (2), 4'-(10-bromode-cyloxy)biphenyl-4-carbonitrile (3), and 4'-(12-bromododecyloxy)biphenyl-4-carbonitrile (4) and characterized their structures, respectively. The extraction abilities of newly synthesized 5-7 toward some selected heavy metal cations, such as Co(2+), Cu(2+), Ni(2+), Zn(2+), Cd(2+), and Hg(2+), were first evaluated and compared by the solvent extraction method. The extraction results revealed that 5-7 were efficient and selective cation receptors for Hg(2+) over-selected cations. On the other hand, the complexation behavior of Hg(2+) with 5-7 was also investigated by using NMR, UV-vis, and IR spectroscopic methods.