Determination of fluoroquinolone antibiotics by microchip capillary electrophoresis along with time-resolved sensitized luminescence of their terbium(III) complexes

Graphene oxide mediated CdSe quantum dots fluorescent aptasensor for high sensitivity detection of fluoroquinolones

In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5-96.9 % and 90.3-95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection.

Usefulness of Hybrid Magnetoliposomes for Aminoglycoside Antibiotic Residues Determination in Food Using an Integrated Microfluidic System with Fluorometric Detection

A new microfluidic approach using hybrid magnetoliposomes (h-MLs) containing hydrophobic magnetic nanoparticles (Fe₃O₄@AuNPs-C12SH) and encapsulated N-acetylcysteine has been developed in this research to determine aminoglycoside antibiotic (AAG) residues in food using o-phthalaldehyde. Four AAGs, kanamycin, streptomycin, gentamicin, and neomycin, have been used as model analytes. The h-MLs have been used for reagent preconcentration and were retained using an external electromagnet device in the reaction/detection zone in a microfluidic system, inserted into the sample chamber of a conventional fluorimeter. The formation of a fluorescent isoindole derivate caused an increase in the luminescence signal, which was proportional to the analyte concentration. The dynamic range of the calibration graph was 0.1-1000 μmol L^-1, expressed as AAG concentration, with an 8.7 nmol L^-1 limit of detection for kanamycin and a sampling frequency of 8 h^-1. The method was applied to determine AAG residues in milk and meat samples with recovery values between 87.2 and 107.4%.

Derivatization of γ-Amino Butyric Acid Analogues for Their Determination in the Biological Samples and Pharmaceutical Preparations: A Comprehensive Review

γ-Aminobutyric acid (GABA) plays an important role in regulating neuronal excitability. Four structurally related drugs to GABA including pregabalin (PGB), gabapentin (GBP), vigabatrin (VGB), and baclofen are used for the treatment of central nervous system disorders. These drugs are small aliphatic molecules having neither fluorescent nor strong absorbance in the ultraviolet/visible region; therefore, direct determination of these analytes by optical methods is difficult. Additionally, their high boiling point makes gas chromatography impossible. Accordingly, the amine or acid moiety in these drugs is derivatized in order to improve their selectivity and sensitivity during determination in the biological samples. This review focuses on derivatization based methods and their different reactions for determination of PGB, GBP, VGB, and baclofen in the biological samples and pharmaceutical preparations reported between 1980 and 2020. High-performance liquid chromatography methods coupled with different detectors are a commonly used methods for determination of GABA analogs after derivatization. These methods cover 38.89% of all developed methods for determination of GABA analogs.

Rapid detection of carbamate pesticide residues using microchip electrophoresis combining amperometric detection

The long-term consumption of food with pesticide residues has harmful effects on human health and the demand for pesticide detection technology tends to be miniaturized and instant. To this end, we demonstrated the first application of indirectly detecting two carbamate pesticides, metolcarb and carbaryl, by gold nanoparticle-modified indium tin oxide electrode in dual-channel microchip electrophoresis and amperometric detection (ME-AD) system. m-Cresol and α-naphthol were obtained after pesticide hydrolysis in alkaline solution, and then separated and detected by ME-AD. Parameters including the detection potential and running buffer concentration and pH were optimized to improve the detection sensitivity and separation efficiency. Under the optimal conditions, the two analytes were completely separated within 80 s. m-Cresol and α-naphthol presented a wide linear range from 1 to 100 μM, with limits of detection of 0.16 μM and 0.34 μM, respectively (S/N = 3). Moreover, the reliability of this system was demonstrated by analyzing metolcarb and carbaryl in spiked vegetable samples.

Integration of a microfluidic system into a conventional luminescence detector using a 3D printed alignment device

A useful 3D printed device for the inside microfluidic integration into a conventional optical detector has been developed. The coupling system supposes the complete integration of a microfluidic device inside the sample compartment of a conventional spectrofluorimeter. For this purpose, a commercial chip-holder, including a microfluidic chip, was anchored inside the detector using a "lab-built" 3D printing alignment prototype. The variables affecting the position of the 3D printed device, such as horizontal and vertical and rotary angles, were optimized. The usefulness of the microfluidic integration system has been tested using an organized suspension of separated hybrid magnetoliposomes containing nanomaterials that were previously separated using a multiphase density gradient centrifugation (MDGC) method. The whole integration system consists of three well-established parts: the impulsion unit, the displacement unit, and the microfluidic chip. The impulsion unit is formed by two syringe pumps, which propel under microflow-rate regime the solutions through to the microfluidic system. The first fluid incorporates an immiscible solution that provides the solution which fills positive oil/water (O/W) displacement unit. In this unit, the previously organized MDGC suspension, which includes different liposome populations, was layer-by-layer displaced to a y-mixer microfluidic chip. The separation content merges with the second solution propelled by the other syringe pump. This solution incorporates a surfactant that promotes the liposome lysis. The novelty supposes the easy incorporation of a 3D printer alignment device, which facilitates the incorporation of the microfluidic channel focused into the optical pathway of the luminescence detector. Graphical abstract.

Quinolone Complexes with Lanthanide Ions: An Insight into their Analytical Applications and Biological Activity

Quinolones comprise a series of synthetic bactericidal agents with a broad spectrum of activity and good bioavailability. An important feature of these molecules is their capacity to bind metal ions in complexes with relevant biological and analytical applications. Interestingly, lanthanide ions possess extremely attractive properties that result from the behavior of the internal 4f electrons, behavior which is not lost upon ionization, nor after coordination. Subsequently, a more detailed discussion about metal complexes of quinolones with lanthanide ions in terms of chemical and biological properties is made. These complexes present a series of characteristics, such as narrow and highly structured emission bands; large gaps between absorption and emission wavelengths (Stokes shifts); and long excited-state lifetimes, which render them suitable for highly sensitive and selective analytical methods of quantitation. Moreover, quinolones have been widely prescribed in both human and animal treatments, which has led to an increase in their impact on the environment, and therefore to a growing interest in the development of new methods for their quantitative determination. Therefore, analytical applications for the quantitative determination of quinolones, lanthanide and miscellaneous ions and nucleic acids, along with other applications, are reviewed here.

A novel fluorescent sensing platform based on metal-polydopamine frameworks for the dual detection of kanamycin and oxytetracycline

In this study, we report the dual detection of kanamycin (KMY) and oxytetracycline (OTC) using metal polydopamine frameworks (MPDA) for the first time. This sensing system employed metal polydopamine frameworks (MPDA), which acted as a fluorescence quencher in the interaction between MPDA and dye-labeled DNA molecules; the metal polydopamine frameworks exhibited an excellent fluorescence quenching behaviour and good analytical response towards the detection of the biomolecules KMY and OTC. The accumulated kanamycin and oxytetracycline in the sensing system were recovered, and changes in their fluorescence intensity were monitored at 525 and 583 nm. Under the optimal conditions, the proposed sensing system remarkably achieved highly sensitive and selective detection of KMY and OTC with the limit of detection of 304 pM and 481 pM, respectively. In addition, the selectivity of the developed sensor was explored in the presence of competitive biomolecules. Moreover, this sensing system demonstrated great potential and versatility for the rapid detection of molecules. In addition, this biosensor was successfully evaluated for the dual detection of KMY and OTC in different real samples.

Determination of baclofen and vigabatrin by microchip electrophoresis with fluorescence detection: application of field-enhanced sample stacking and dynamic pH junction

A novel microchip gel electrophoretic method for the assay of baclofen and vigabatrin for the first time.

Analysis of antibiotics by CE and their use as chiral selectors: An update

The widespread use of antibiotics in medicine and as growth-promoting agents has increased the demand for suitable analytical techniques for their analysis. Analytical methods based on CE or miniaturized CE systems have proved over the years their ability for the analysis of antibiotics. Since our last review (Electrophoresis 2014, 35, 28-49) several new CE methodologies have been reported for antibiotic analysis. This review presents an update of the literature published from June 2013 to June 2015 for the analysis of antibiotics by CE. UV continues being the most used detection system for antibiotics analysis by CE. Strategies to improve sensitivity as the use of sensitive detection systems and the application of preconcentration techniques appear to be the major developments. Furthermore, the use of portable and miniaturized devices for antibiotic analysis is presented in detail. Applications of the developed methodologies to the determination of residues of antibiotics in biological, food, and environmental samples are carefully described. Finally, new developments and applications of antibiotics as chiral selectors in CE are also included.