Voltammetric sensor system based on Cu(II) and Zn(II) amino acid complexes for recognition and determination of atenolol enantiomers

Functionalized Chiral Materials for Use in Chiral Sensors

Chirality represents a fundamental attribute within living systems and is a pervasive phenomenon in the natural world. The identification and analysis of chiral materials within natural environments and biological systems hold paramount importance in clinical, chemical, and biological sciences. Within chiral analysis, there is a burgeoning focus on developing chiral sensors exhibiting exceptional selectivity, sensitivity, and stability, marking it as a forefront area of research. In the past decade (2013-2023), approximately 1990 papers concerning the application of various chiral materials in chiral sensors have been published. Biological materials and nanomaterials have important applications in the development of chiral sensors, which accounting for 26.67% and 45.24% of the material-related applications in these sensors, respectively; moreover, the development of chiral nanomaterials is closely related to the development of portable and stable chiral sensors. Natural chiral materials, utilized as selective recognition units, are combined with carriers characterized by good physical and chemical properties through functionalization to form various functional chiral materials, which improve the recognition efficiency of chiral sensors. In this article, from the perspective of biological materials, polymer materials, nanomaterials, and other functional chiral materials, the applications of chiral sensors are summarized and the research prospects of chiral sensors are discussed.

Derivatization-free conventional and synchronous spectrofluorimetric estimation of atenolol and amlodipine

Fixed-dose combinations for treatment of hypertension are observed in many dosages in the global market because of their high efficacy compared to single component dosage forms. One of these effective combinations is atenolol/amlodipine which is usually administered to patients with hypertension. Hence, development of facile, accurate, and sensitive methods for simultaneous estimation of atenolol and amlodipine is of great importance for quality control testing and pharmacokinetic studies. In our study, we developed two spectrofluorimetric methods to estimate both compounds in different pharmaceuticals. The first method is based on the estimation of atenolol and amlodipine by double-scan conventional spectrofluorimetry where the fluorescence intensities of atenolol and amlodipine were measured at 299 and 434 nm after excitation at 274 and 358 nm, respectively. The second method depends on synchronous spectrofluorimetric measurements at Δλ = 70 nm, where atenolol is assayed at 266 nm and amlodipine is assayed at 363 nm. Methods' optimizations were carried out to select the optimum conditions that render high selectivity and sensitivity. Such optimizations included assessment of solvents, surfactants, buffer volumes and pHs. The conventional spectrofluorimetric method was rectilinear over concentration range of 30.0-300.0 ng mL-1 for atenolol and 0.25-7.00 µg mL-1 for amlodipine while the synchronous spectrofluorimetric method showed linearity over the ranges of 0.60-6.00 µg mL-1 for atenolol and 0.25-7.00 µg mL-1 for amlodipine with low detection limits (≤0.12 µg mL-1) for both compounds in the two methods. It is the first work that demonstrates estimation of atenolol and amlodipine in their combinations by conventional and synchronous spectrofluorimetry. Both methods were applied to estimate atenolol and amlodipine in different pharmaceuticals with high %recovery and low %RSD.

Label-free green estimation of atenolol and ivabradine hydrochloride in pharmaceutical and biological matrices by synchronous spectrofluorimetry

In this work, a label-free, rapid, and sensitive synchronous spectrofluorometric method was implemented to assay atenolol (ATL) and ivabradine hydrochloride (IVB) in pharmaceutical and biological matrices. Simultaneous determination of ATL and IVB by conventional spectrofluorometry cannot be implemented because of the clear overlap of the emmision spectra of ATL and IVB. To overcome this problem, synchronous fluorescence measurements at a constant wavelength difference (Δλ) combined with mathematical derivatization of the zero order spectra were perforemed. The results indicated a good resolution between emission spectra of the studied drugs when the first-order derivative of the synchronous fluorescence scans at Δλ = 40 nm was conducted using ethanol as the optimum solvent which is less hazardous than other organic solvents such as methanol and acetonitrile, keeping the method safe and green. The amplitudes of the first derivative synchronous fluorescent scans of ATL and IVB in ethanol were monitored at 286 and 270 nm to simultaneously estimate ATL and IVB, respectively. Method optimisation was conducted by assessing different solvents, buffer pHs, and surfactants. The optimum results were obtained when ethanol was utilized as a solvent without using any other additives. The developed method was linear over concentration ranges of 10.0-250.0 ng mL^-1 for IVB and 100.0-800.0 ng mL^-1 for ATL with detection limits of 3.07 and 26.49 ng mL^-1 for IVB and ATL, respectively. The method was utilized to assay the studied drugs in their dosages and in human urine samples with acceptable % recoveries and RSD values. The greenness of the method was implemented by three approaches involving the recently reported metric (AGREE) which ensured the eco-freindship and safety of the method.

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term "nano" is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms "nano" and "enantiomer separation" on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.

Chiral Selectors in Voltammetric Sensors Based on Mixed Phenylalanine/Alanine Cu(II) and Zn(II) Complexes

A practical application composite based on mixed chelate complexes [M(S-Ala)2(H2O)n]–[M(S-Phe)2(H2O)n] (M = Cu(II), Zn(II); n = 0–1) as chiral selectors in enantioselective voltammetric sensors was suggested. The structures of the resulting complexes were studied by XRD, ESI-MS, and IR- and NMR-spectroscopy methods. It was determined that enantioselectivity depends on the metal nature and on the structure of the mixed complex. The mixed complexes, which were suggested to be chiral selectors, were stable under the experimental conditions and provided greater enantioselectivity in the determination of chiral analytes, such as naproxen and propranolol, in comparison with the amino acids they comprise. The best results shown by the mixed copper complex [Cu(S-Ala)2]–[Cu(S-Phe)2] were: ipS/ipR = 1.27 and ΔEp = 30 mV for Nap; and ipS/ipR = 1.37 and ΔEp = 20 mV for Prp. The electrochemical and analytical characteristics of the sensors and conditions of voltammogram recordings were studied by differential pulse voltammetry. Linear relationships between the anodic current and the concentrations of Nap and Prp enantiomers were achieved in the range of 2.5 × 10−5 to 1.0 × 10−3 mol L−1 for GCE/PEC-[Cu(S-Ala)2]–[Cu(S-Phe)2] and 5.0 × 10−5 to 1.0 × 10−3 for GCE/PEC–[Zn(S-Ala)2(H2O)]–[Zn(S-Phe)2(H2O)], with detection limits (3 s/m) of 0.30–1.24 μM. The suggested sensor was used to analyze Nap and Prp enantiomers in urine and plasma samples.