Liquid chromatography–tandem mass spectrometry for rapid and selective simultaneous determination of fluoroquinolones level in human aqueous humor

Development of a Screening Method for Fluoroquinolones in Meat Samples Using Molecularly Imprinted Carbon Dots

An accurate and simple screening method has been developed for the determination of fluoroquinolone antibiotics. Carbon dots were synthesized by simple hydrothermal treatment as highly fluorescent nano-sensors. They were subsequently used in the synthesis of organic-based molecularly imprinted polymers to develop fluorescence-based polymeric composites using enoxacin as a representative dummy template molecule of fluoroquinolones. The method was optimized concerning the pH of the medium and composite concentration. The normalized fluorescence intensity showed efficient quenching under optimized conditions upon successive addition of the template, with an excellent correlation coefficient. The proposed method was applied to eight other fluoroquinolones, exhibiting, in all cases, good correlation coefficients (0.65-0.992) within the same linearity range (0.03-2.60 mg mL-1). Excellent detection and quantification limits were been obtained for the target analytes down to 0.062 and 0.186 mg L-1, respectively. All studied analytes showed no interference with enrofloxacin, the most commonly used veterinary fluoroquinolone, with a percentage of cross-reactivity varying from 89.00 to 540.00%. This method was applied successfully for the determination of enrofloxacin in three different types of meat samples: beef, pork, and chicken, with good recoveries varying from 70 to 100% at three levels. This new procedure is an easy analytical method that can be useful as a screening method for monitoring the environmental hazard of fluoroquinolones in quality control laboratories.

Development and Comparative Evaluation of Ciprofloxacin Nanoemulsion-Loaded Bigels Prepared Using Different Ratios of Oleogel to Hydrogels

Nanoemulsions and bigels are biphasic delivery systems that can be used for topical applications. The aim of this study was to incorporate an oil-in-water ciprofloxacin hydrochloride nanoemulsion (CIP.HCl NE) into two types of bigels, Type I (oleogel (OL)-in-hydrogel (WH)) and Type II (WH-in-OL) to enhance drug penetration into skin and treat topical bacterial infections. Bigels were prepared at various ratios of OL and WH (1:1, 1:2, and 1:4). Initially, CIP.HCl NE was prepared and characterized in terms of droplet size, zeta potential, polydispersity index, morphology, and thermodynamic and chemical stability. Then CIP.HCl NE was dispersed into the OL or WH phase of the bigel. The primary physical stability studies showed that Type I bigels were physically stable, showing no phase separation. Whereas Type II bigels were physically unstable, hence excluded from the study. Type I bigels were subjected to microstructural, rheological, in vitro release, antimicrobial, and stability studies. The microscopic images showed a highly structured bigel network with nanoemulsion droplets dispersed within the bigel network. Additionally, bigels exhibited pseudoplastic flow and viscoelastic properties. A complete drug release was achieved after 4-5 h. The in vitro and ex vivo antimicrobial studies revealed that bigels exhibited antimicrobial activity against different bacterial strains. Moreover, stability studies showed that the rheological properties and physical and chemical stability varied based on the bigel composition over three months. Therefore, the physicochemical and rheological properties, drug release rate, and antimicrobial activity of Type I bigels could be modified by altering the OL to WH ratio and the phase in which the nanoemulsion dispersed in.

Evaluation of the effect of gentamicin in surgical perfusion solution on cataract postoperative endophthalmitis

Objective

To evaluate the effect of gentamicin in surgical perfusion solution on endophthalmitis incidence after cataract surgery.

Methods

A retrospective analysis of endophthalmitis incidence was conducted in two groups of patients who underwent cataract surgery, with (Group B) or without gentamicin (Group A) in the surgical perfusion solution. Endophthalmitis incidence, the isolated pathogenic bacteria strains and their antibiotic sensitivity, and the drug-resistant genotype of the pathogens were examined.

Results

The incidence of endophthalmitis in patients of group A was 0.8‰. Thirteen pathogenic bacterial strains were isolated from the patient samples in group A, including 8 strains of Staphylococcus epidermidis, 1 Staphylococcus aureus, 1 Streptococcus pneumoniae, 1 Streptococcus bovis, 1 Enterococcus faecium and 1 Morganella sp. The incidence of endophthalmitis in group B patients was 0.2‰, which was significantly lower than that in group A (P<0.05). Five strains of pathogenic bacteria were successfully isolated, including 2 strains of Enterococcus faecium, 1 Enterococcus faecalis, 1 Staphylococcus epidermidis and 1 Staphylococcus aureus. There was no significant difference in the proportion of Staphylococcus strains in all isolated bacteria between the two groups (P > 0.05). However, the proportion of Enterococci isolated in group B samples was higher than that in group A (P < 0.05). There were more gentamicin-sensitive strains than levofloxacin-sensitive strains identified (P < 0.05). Interestingly, aminoglycoside-inactivating enzyme resistance gene was detected in Enterococcus strains.

Conclusion

Our data suggest that gentamicin-containing perfusion solution can reduce the incidence of postoperative endophthalmitis in cataract patients. However, the selective pressure imposed by gentamicin may facilitate the development of aminoglycoside-resistant Enterococcos strains.

A sensitive aptasensor based on rolling circle amplification and G-rich ssDNA/terbium (III) luminescence enhancement for ofloxacin detection in food

As the light-harvesting "antenna", G-rich oligonucleotides (such as the G-quadruplex) can interact with lanthanide (III) to bring a luminescent enhancement response. In this study, phenomenon of luminescent enhancement of G-triplex/terbium (III) (G3/Tb³⁺) and interaction between G3 and Tb³⁺ were first reported and characterized. Based on G3/Tb³⁺ luminescence, a label-free aptasensor for the detection of ofloxacin (OFL) residues in the food was developed. The OFL triggered the action of rolling circle amplification (RCA) allowed for the amplification product of G3-forming sequences in the single-stranded DNA, which promoted the conformational transition of the G3/Tb³⁺ complexes once the addition of Tb³⁺. Under the optimal conditions, the logarithmic correlation between the G3/Tb³⁺ luminescence intensity and the concentration of OFL was found to be linear in the range of 5-1000 pmol L^-1 (R² = 0.9949). The limit of detection was 0.18 pmol L^-1 (3σ/slope). Additionally, the good recoveries of 90.19-108.89 % and the relative standard deviations values of 0.59-5.87 % were obtained in the application of the aptasensor detecting OFL in the practical samples. These results confirmed that the present aptasensor has a good analytical performance and bright prospect for detecting ofloxacin residues in food.

Lactate and pyruvate levels correlation with lactate dehydrogenase gene expression and glucose consumption in Tamoxifen-resistant MCF-7 cells using capillary electrophoresis with contactless conductivity detection (CE-C4 D)

Breast cancer is the second leading cause of cancer death in women after lung cancer. The first-line treatment of metastatic breast cancer in premenopausal women relies on tamoxifen. The development of tamoxifen resistance is not fully understood. In this study, capillary electrophoresis with capacitively coupled contactless conductivity detector was developed to monitor the changes in lactate and pyruvate levels in supernatant media of three models of developed MCF-7 tamoxifen-resistant cells and correlate these metabolites changes with lactate dehydrogenase genes expression and glucose consumption. The electrophoretic separation was achieved under reversed electroosmotic flow conditions. The linear ranges were 0.15-5 and 0.01-1 mM with a correlation coefficient of 0.9966 and 0.9971 and the limits of detection were 0.01 and 0.02 μM for lactate and pyruvate, respectively. Inter- and intrarun accuracy were in the range of 96.88-105.94% with precision (CV, %) of ≤7.35%. The method was completely validated and the results were in agreement with those obtained using the lactate and glucose assay kits. The results revealed a significant increase in both lactate and pyruvate production in the three tamoxifen-resistant MCF-7 cells models compared to control cells. This increase was correlated with the increase of lactate dehydrogenase genes expression and the increase of glucose consumption.

High Performance Liquid Chromatography-Tandem Mass Spectrometry Method for Correlating the Metabolic Changes of Lactate, Pyruvate and L-Glutamine with Induced Tamoxifen Resistant MCF-7 Cell Line Potential Molecular Changes

Breast cancer is one of the most prevalent cancers worldwide usually treated with Tamoxifen. Tamoxifen resistance development is the most challenging issue in an initially responsive breast tumor, and mechanisms of resistance are still under investigation. The objective of this study is to develop and validate a selective, sensitive, and simultaneous high performance liquid chromatography–tandem mass spectrometry method to explore the changes in substrates and metabolites in supernatant media of developed Tamoxifen resistance MCF-7 cells. We focus on the determination of lactate, pyruvate, and L-glutamine which enables the tracking of changes in metabolic pathways as a result of the resistance process. Chromatographic separation was achieved within 3.5 min. using a HILIC column (4.6 × 100 mm, 3.5 µm particle size) and mobile phase of 0.05 M acetic acid–ammonium acetate buffer solution pH 3.0: Acetonitrile (40:60 v/v). The linear range was 0.11–2.25, 0.012–0.227, and 0.02–0.20 mM for lactate, pyruvate, and L-glutamine, respectively. Within- and between-run accuracy was in the range 98.94-105.50% with precision (CV, %) of ≤0.86%. The results revealed a significant increase in both lactate and pyruvate production after acquiring the resistant. An increase in L-glutamine levels was also observed and could be attributed to its over production or decline in its consumption. Therefore, further tracking of genes responsible of lactate, pyruvate, and glutamine metabolic pathways should be performed in parallel to provide in-depth explanation of resistance mechanism.

Recent development of antibiotic detection in food and environment: the combination of sensors and nanomaterials

In recent years, the abuse of antibiotics has led to the pollution of soil and water environment, not only poultry husbandry and food manufacturing will be influenced to different degree, but also the human body will produce antibody. The detection of antibiotic content in production and life is imperative. In this review, we provide comprehensive information about chemical sensors and biosensors for antibiotic detection. We classify the currently reported antibiotic detection technologies into chromatography, mass spectrometry, capillary electrophoresis, optical detection, and electrochemistry, introduce some representative examples for each technology, and conclude the advantages and limitations. In particular, the optical and electrochemical methods based on nanomaterials are discussed and evaluated in detail. In addition, the latest research in the detection of antibiotics by photosensitive materials is discussed. Finally, we summarize the pros and cons of various antibiotic detection methods and present a discussion and outlook on the expansion of cross-scientific areas. The synthesis and application of optoelectronic nanomaterials and aptamer screening are discussed and prospected, and the future trends and potential impact of biosensors in antibiotic detection are outlined.Graphical abstract.

Selective extraction and enhanced-sensitivity detection of fluoroquinolones in swine body fluids by liquid chromatography-high resolution mass spectrometry: Application in long-term monitoring in livestock

To ensure food safety in livestock industries, developing a non-lethal and cost-effective detection method for the long-term monitoring of veterinary antibiotics in animals will be beneficial to avoid unnecessary losses. In this study, a highly-selective extraction using dispersive micro solid-phase extraction method coupled with an enhanced-sensitivity detection by pre-column dilution injection and liquid chromatography-high resolution mass spectrometry was used to determine the restricted fluoroquinolones (FQs) in swine body fluids. The proposed method showed good linear coefficients higher than 0.999, and high sensitivity with the LODs and LOQs in the range of 0.02-0.03 μg/L and 0.06-0.1 μg/L in swine body fluids, respectively. For further evaluation, the adequate recoveries (85.3-112.8%), satisfactory repeatability (intra-day and inter-day precisions of 2.1%-8.2% and 3.8%-13.7%, respectively), and acceptable matrix effect (0.92-1.12) of the FQs were achieved. It has been successfully applied for analysis of the FQs in body fluids without sacrificing animals in the future.

Rapid and simultaneous determination of three fluoroquinolones in animal-derived foods using excitation-emission matrix fluorescence coupled with second-order calibration method

The matter of fluoroquinolone residues in various foods still arouses wide public concern nowadays. In the present work, the strategy of excitation-emission matrix (EEM) fluorescence data coupled with second-order calibration method based on alternating normalization-weighted error (ANWE) algorithm was used to determine ofloxacin, lomefloxacin and ciprofloxacin in milk powder, milk and beef. Owning the unique "second-order advantage", the ANWE-assisted analytical method was proved to successfully and eco-friendly resolve the overlapped fluorescence spectra of multi-component in complex food matrixes without tedious pretreatment steps and sophisticated high-cost instrumentations. The feasibility of the proposed method was validated by experiments. The average spiked recoveries of three fluoroquinolones range from 82.6% to 110.5% with relative standard deviations lower than 7.4%, and the limits of detection range from 0.18 and 2.41 ng mL^-1. For further evaluation, analytical figures of merit such as sensitivity and selectivity, as well as the RSDs of intra-day (≦10.6%) and inter-day (≦9.4%) were calculated. The satisfactory analytical results demonstrated that the proposed strategy could be a competitive alternative for simple, rapid and simultaneous determination of multiple fluoroquinolones in animal-derived food samples.

Fluorescent aptasensor for ofloxacin detection based on the aggregation of gold nanoparticles and its effect on quenching the fluorescence of Rhodamine B

This paper proposes the idea of building a fluorescent biosensor for ofloxacin (OFL) determination in aqueous and milk samples by label-free OFL-specific aptamer, gold nanoparticles (AuNPs) and Rhodamine B (RB). In the absence of OFL, AuNPs are coated with OFL aptamer and maintain dispersed in the high concentration of NaCl. The dispersed AuNPs could reduce the strong fluorescence intensity of RB efficiently. By contrast, in the presence of OFL, OFL is combined with aptamer to form stable compounds, causing the aptamers separated from the surface of AuNPs, thus AuNPs would be exposed in the solution. And the aggregated AuNPs will not quench the fluorescence intensity of RB. Through the distinction of the fluorescence intensity, the concentration of OFL could be detected in aqueous and milk samples quantitatively. The convenient and specific fluorescent assay for OFL is established with a linear range (R = 0.9907) from 20 to 300 nM and a detection limit of 1.66 nM in aqueous solution, and a linear range (R = 0.9963) from 20 to 300 nM and a detection limit of 4.61 nM (1.66 μg/L) in milk samples. With the good sensitivity and selectivity, this biosensor has good application potential to detect OFL in food and environmental samples.