Luminescent and time-resolved determination of gemifloxacin mesylate in pharmaceutical formulations and spiked blood plasma samples using a lanthanide complex as a probe.

A novel luminescence-based analytical methodology was established employing a europium(III) complex with 3-allyl-2-hydroxybenzohydrazide (HAZ) as the coordinating ligand for the quantification of gemifloxacin mesylate (GMF) in pharmaceutical preparations and human plasma samples spiked with the compound. The stoichiometry of the europium complex with HAZ was determined the Job plot and exhibited a metal-to-ligand ratio of 1 : 2. The analytical procedure relies on a rapid and significant enhancement of luminescence by the Eu(AZ) complex when it interacts with gemifloxacin mesylate, which allowed for the rapid detection of 96 samples within approximately 2 minutes.

New terbium complex as a luminescent probe for determination of chlorogenic acid in green coffee and roasted coffee infusions.

Green coffee is coming into vogue as a food that contains remarkable contents of antioxidants like chlorogenic acid (ChA) and induces mild stimulation to the consumer. While most methods for determination of ChA require chromatographic separation prior its quantitation, we present the first probe and a simple, sensitive and validated luminescence method for the determination of chlorogenic acid in green and roasted coffee infusion samples that does not require a chromatographic separation. ChA can remarkably quench the luminescence intensity of the Tb complex with 1-(furan-2-ylmethyl)-4-hydroxy-N-(4-methylpyridin-2-yl)-2-oxo-1,2,5,6,7,8-hexahydroquinoline-3-carboxamide (R) in aqueous solution containing urotropine buffer at a near neutral pH 7.

Critical review of polymer and hydrogel deposition methods for optical and electrochemical bioanalytical sensors correlated to the sensor's applicability in real samples.

Sensors, ranging from in vivo through to single-use systems, employ protective membranes or hydrogels to enhance sample collection or serve as filters, to immobilize or entrap probes or receptors, or to stabilize and enhance a sensor's lifetime. Furthermore, many applications demand specific requirements such as biocompatibility and non-fouling properties for in vivo applications, or fast and inexpensive mass production capabilities for single-use sensors. We critically evaluated how membrane materials and their deposition methods impact optical and electrochemical systems with special focus on analytical figures of merit and potential toward large-scale production.

Next generation luminol derivative as powerful benchmark probe for chemiluminescence assays.

Chemiluminescence (CL) provides outstanding analytical performance due to its independence from external light sources, background-free nature and exceptional sensitivity and selectivity. Yet, ultra-sensitive (bio)analysis is impeded by low hydrophilicity, poor quantum yields, fast kinetics or instability of most CL reagents such as luminol, acridinium esters, dioxetanes or peroxyoxalic derivatives. Photophysical studies show that m-carboxy luminol overcomes these limitations as its hydrophilic design provides a 5-fold increase in relative quantum yield resulting in superior performance in HO-dependent bioassays with 18-fold higher sensitivity for the quantification of its co-reactant HO, and 5-times lower detection limits for the luminophore.

Highly sensitive interleukin 6 detection by employing commercially ready liposomes in an LFA format.

Recent years have confirmed the ubiquitous applicability of lateral flow assays (LFA) in point-of-care testing (POCT). To make this technology available for low abundance analytes, strategies towards lower limits of detections (LOD), while maintaining the LFA's ease of use, are still being sought. Here, we demonstrate how liposomes can significantly improve the LOD of traditional gold nanoparticle (AuNP)-based assays while fully supporting a ready-to-use system for commercial application.

Isoquinoline-based Eu(iii) luminescent probes for citrate sensing in complex matrix.

A neutral Eu(iii) complex containing the S,S enantiomer of isoQC3A ligand (isoQC3A = N-isoquinolyl-N,N',N'-trans-l,2-cyclohexylenediaminetriacetate) was synthesized and characterized. The complex was spectroscopically investigated and the results compared with those obtained for the similar bis-anionic ligand bisoQcd (bisoQcd = N,N'-bis(2-isoquinolinmethyl)-trans-1,2-diaminocyclohexane N,N'-diacetate). Both Eu(iii)-complexes show similar binding constants upon titration with the main analytes contained in interstitial extracellular fluid (i.

Electrochemical multi-analyte point-of-care perspiration sensors using on-chip three-dimensional graphene electrodes.

Multi-analyte sensing using exclusively laser-induced graphene (LIG)-based planar electrode systems was developed for sweat analysis. LIG provides 3D structures of graphene, can be manufactured easier than any other carbon electrode also on large scale, and in form of electrodes: hence, it is predestinated for affordable, wearable point-of-care sensors. Here, it is demonstrated that LIG facilitates all three electrochemical sensing strategies (voltammetry, potentiometry, impedance) in a multi-analyte system for sweat analysis.

Optical sensors for determination of biogenic amines in food.

This review presents the state-of-the-art of optical sensors for determination of biogenic amines (BAs) in food by publications covering about the last 10 years. Interest in the development of rapid and preferably on-site methods for quantification of BAs is based on their important role in implementation and regulation of various physiological processes. At the same time, BAs can develop in different kinds of food by fermentation processes or microbial activity or arise due to contamination, which induces toxicological risks and food poisoning and causes serious health issues.

Cationic liposomes for generic signal amplification strategies in bioassays.

Liposomes have been widely applied in bioanalytical assays. Most liposomes used bare negative charges to prevent non-specific binding and increase colloidal stability. Here, in contrast, highly stable, positively charged liposomes entrapping the fluorescent dye sulforhodamine B (SRB) were developed to serve as a secondary, non-specific label' and signal amplification tool in bioanalytical systems by exploiting their electrostatic interaction with negatively charged vesicles, surfaces, and microorganisms.

Magnetosomes for bioassays by merging fluorescent liposomes and magnetic nanoparticles: encapsulation and bilayer insertion strategies.

Magnetized liposome (magnetosomes) labels can overcome diffusion limitations in bioassays through fast and easy magnetic attraction. Our aim therefore was to advance the understanding of factors influencing their synthesis focusing on encapsulation strategies and synthesis parameters. Magnetosome synthesis is governed by the surface chemistry and the size of the magnetic nanoparticles used.

Shedding Light on the Diversity of Surfactant Interactions with Luminol Electrochemiluminescence for Bioanalysis.

Luminol is a major probe for chemiluminescence (CL) and electrochemiluminescence (ECL) detection technologies in (bio)analysis. Surfactants are added to ECL assay cocktails to enhance signals or are present, owing to given bioassay protocols, yet little is known regarding their effects on luminol ECL. In-depth understanding is provided here through a broad study with bioanalytically relevant surfactants (cationic, anionic, and nonionic), four common electrode materials, and two luminol derivatives.

Tethering functionality to lipid interfaces by a fast, simple and controllable post synthesis method.

Hypothesis: Liposomes require careful control of the surface design to ensure colloidal stability in complex matrices and target-specific binding to desired receptor units. Ideally, surface functionalization should be smart and controllable in terms of composition which is seldomly achieved by conventional methods. Therefore, a new strategy (insertion method) was developed and compared to the standard method (modification post-synthesis) using the model receptor biotin.

Nanocontainers for Analytical Applications.

Nanocontainers such as mesoporous silica particles and polymersomes are versatile structures containing holes or pores which are used for the entrapment of small molecules and the introduction of specific functionalities. They are widely applied in drug delivery, biomedicine, bioreactors, and analytical applications. In the last case, nanocontainers usually serve as amplification systems.

A luminescent europium complex for wide-range pH sensors and sensor microtiterplates.

In this work, we show a new concept of a luminescent wide-range pH indicator based on a europium complex and its implementation in sensors and sensor microtiterplates. For this purpose, we complexed europium with the ligands gallic acid (Gall) and pyridine dicarboxylic acid (PDA) that carry groups with wide ranging pK values and the antenna ligand theonyl trifluoroacetone (TTA). This yields an indicator that overcomes the typical drawbacks of many optical pH indicator dyes which mostly cover three pH units, only.

Electrochemiluminescence Bioassays with a Water-Soluble Luminol Derivative Can Outperform Fluorescence Assays.

The most efficient and commonly used electrochemiluminescence (ECL) emitters are luminol, [Ru(bpy) ] , and derivatives thereof. Luminol stands out due to its low excitation potential, but applications are limited by its insolubility under physiological conditions. The water-soluble m-carboxy luminol was synthesized in 15 % yield and exhibited high solubility under physiological conditions and afforded a four-fold ECL signal increase (vs.

Functional electrospun nanofibers for multimodal sensitive detection of biogenic amines in food via a simple dipstick assay.

Electrospun nanofibers (ENFs) are promising materials for rapid diagnostic tests like lateral flow assays and dipsticks because they offer an immense surface area while excluding minimal volume, a variety of functional surface groups, and can entrap functional additives within their interior. Here, we show that ENFs on sample pads are superior in comparison to standard polymer membranes for the optical detection of biogenic amines (BAs) in food using a dipstick format. Specifically, cellulose acetate (CA) fibers doped with 2 mg/mL of the chromogenic and fluorogenic amine-reactive chameleon dye Py-1 were electrospun into uniform anionic mats.

Improving ruthenium-based ECL through nonionic surfactants and tertiary amines.

The influence of surfactants and coreactants on Ru(bpy) electrogenerated chemiluminescence (ECL) was investigated comparatively. Specifically, the influence that the two tertiary amines, N-butyldiethanolamine (NBEA) and 2-(dibutylamino)ethanol (DBAE) have on the ECL reaction, alone and in the presence of the two surfactants Triton™ X-100 and Zonyl® FSN, was investigated, in comparison with that of the well-studied and established coreactant tripropylamine (TPA). Experiments were conducted on poly(methyl methacrylate) substrates coated with plasma-evaporated gold as used in many miniaturized systems.

Signal enhancement and low oxidation potentials for miniaturized ECL biosensors via N-butyldiethanolamine.

We present studies on ruthenium-based electrochemiluminescence (ECL) focusing on conditions supporting signal enhancement and low oxidation potentials. Low oxidation potentials (LOPs) are especially attractive for miniaturized ECL biosensors, as microfabricated electrodes tend to detach from their support when used with high currents and operated at high potentials. Furthermore, high potentials or current densities can lead to damage of typical biosensor surface coatings and biological probes.

Design, selective alkylation and X-ray crystal structure determination of dihydro-indolyl-1,2,4-triazole-3-thione and its 3-benzylsulfanyl analogue as potent anticancer agents.

Three sets of substituted indolyl-triazoles were synthesized by the alkylation of 1,2-dihydro-5-(1H-indol-2-yl)-1,2,4-triazole-3-thione with different alkyl halides. The use of pyridine restricted the alkylation to sulfur. Whereas, upon using KCO, the alkylation exceeded sulfur to one of the remaining triazole nitrogens.

Validation of a Fluorescence Sensor Microtiterplate for Biogenic Amines in Meat and Cheese.

An optical sensor microtiterplate for quantitative analysis of the total content of biogenic amines (TAC) in meat and cheese was developed and validated for the first time. In the plate, a chameleon dye (Py-1) is embedded in a polymeric cocktail which is deposited on the bottom of the wells in a common microtiterplate. On reaction with biogenic amines (BAs), the fluorescence of Py-1 at 620 nm rapidly delivers a precise TAC.

Regioselectivity of the alkylation of S-substituted 1,2,4-triazoles with dihaloalkanes.

Background: 1,2,4-Triazole3-thiones are good scaffolds for preparation of new lead compounds. Their derivatives attracted the attention of chemists due to their wide spectrum of biological activities. Alkylsulfanyl-1,2,4-triazoles have three nucleophilic sites (nitrogens) ready for reaction with electrophiles.

Enzyme-Based Test Strips for Visual or Photographic Detection and Quantitation of Gaseous Sulfur Mustard.

Sulfur mustard is a chemical agent of high military and terroristic significance. No effective antidote exists, and sulfur mustard can be fairly easily produced in large quantity. Rapid field testing of sulfur mustard is highly desirable.

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors.

Glycosylations of 5-(1H-indol-2-yl)-1,3,4-oxadiazoline-2(3H)-thione delivered various degrees of S- and/or N-glycosides depending on the reaction conditions. S-Glycosides were obtained regiospecifically by grinding oxadiazolinethiones with acylated α-D-glycosyl halides in basic alumina, whereas 3-N-(glycosyl)oxadiazolinethiones were selectively obtained by reaction with HgCl(2) followed by heating the resultant chloromercuric salt with α-D-glycosyl halides in toluene under reflux. On using Et(3)N or K(2)CO(3) as a base, mixtures of S- (major degree) and N-glycosides (minor degree) were obtained.