Physicochemical properties of pH-controlled polyion complex (PIC) micelles of poly(acrylic acid)-based double hydrophilic block copolymers and various polyamines

in Analytical and Bioanalytical Chemistry (2012), 403

The physicochemical properties of polyion complex (PIC) micelles were investigated in order to characterize the cores constituted of electrostatic complexes of two oppositely charged polyelectrolytes. The ... [more ▼]

The physicochemical properties of polyion complex (PIC) micelles were investigated in order to characterize the cores constituted of electrostatic complexes of two oppositely charged polyelectrolytes. The pH-sensitive micelles were obtained with double hydrophilic block copolymers containing a poly(acrylic acid) block linked to a modified poly(ethylene oxide) block and various polyamines (polylysine, linear and branched polyethyleneimine, polyvinylpyridine, and polyallylamine). The pH range of micellization in which both components are ionized was determined for each polyamine. The resulting PIC micelles were characterized using dynamic light scattering and smallangle X-ray scattering experiments (SAXS). The PIC micelles presented a core–corona nanostructure with variable polymer density contrasts between the core and the corona, as revealed by the analysis of the SAXS curves. It was shown that PIC micelle cores constituted by polyacrylate chains and polyamines were more or less dense depending on the nature of the polyamine. It was also determined that the density of the cores of the PIC micelles depended strongly on the nature of the polyamine. These homogeneous cores were surrounded by a large hairy corona of hydrated polyethylene oxide block chains. Auramine O (AO) was successfully entrapped in the PIC micelles, and its fluorescence properties were used to get more insight on the core properties. Fluorescence data confirmed that the cores of such micelles are quite compact and that their microviscosity depended on the nature of the polyamine. The results obtained on these core–shell micelles allow contemplating a wide range of applications in which the AO probe would be replaced by various cationic drugs or other similarly charged species to form drug nanocarriers or new functional nanodevices. [less ▲]

Innovative methodology to transfer conventional GC-MS heroin profiling to UHPLC-MS/MS

in Analytical and Bioanalytical Chemistry (2011), 399(8), 2719-2730

Nowadays, in forensic laboratories, heroin profiling is frequently carried out by gas chromatography coupled with mass spectrometry (GC-MS). This analytical technique is well established, provides good ... [more ▼]

Nowadays, in forensic laboratories, heroin profiling is frequently carried out by gas chromatography coupled with mass spectrometry (GC-MS). This analytical technique is well established, provides good sensitivity and reproducibility, and allows the use of large databases. Despite those benefits, recently introduced analytical techniques, such as ultra-high-pressure liquid chromatography (UHPLC), could offer better chromatographic performance, which needs to be considered to increase the analysis throughput for heroin profiling. With the latter, chromatographic conditions were optimized through commercial modeling software and two atmospheric pressure ionization sources were evaluated. Data obtained from UHPLC–MS/MS were thus transferred, thanks to mathematical models to mimic GC-MS data. A calibration and a validation set of representative heroin samples were selected among the database to establish a transfer methodology and assess the models’ abilities to transfer using principal component analysis and hierarchical classification analysis. These abilities were evaluated by computing the frequency of successful classification of UHPLC–MS/MS data among GC-MS database. Seven mathematical models were tested to adjust UHPLC–MS/MS data to GC-MS data. A simplified mathematical model was finally selected and offered a frequency of successful transfer equal to 95%. [less ▲]

Mass spectrometry imaging of rat brain sections: nanomolar sensitivity with MALDI versus nanometer resolution by TOF–SIMS

in Analytical and Bioanalytical Chemistry (2010), 396(1), 151-162

Mass spectrometry imaging is becoming a more and more widely used method for chemical mapping of organic and inorganic compounds from various surfaces, especially tissue sections. Two main different ... [more ▼]

Mass spectrometry imaging is becoming a more and more widely used method for chemical mapping of organic and inorganic compounds from various surfaces, especially tissue sections. Two main different techniques are now available: matrix-assisted laser desorption/ionizaton, where the sample, preliminary coated by an organic matrix, is analyzed by a UV laser beam; and secondary ion mass spectrometry, for which the target is directly submitted to a focused ion beam. Both techniques revealed excellent performances for lipid mapping of tissue surfaces. This article will discuss similarities, differences, and specificities of ion images generated by these two techniques in terms of sample preparation, sensitivity, ultimate spatial resolution, and structural analysis. [less ▲]

Quantitative methods for food allergens: a review.

in Analytical and Bioanalytical Chemistry (2009), 395

The quantitative detection of allergens in the food chain is a strategic health objective as the prevalence of allergy continues to rise. Food allergenicity is caused by proteins either in their native ... [more ▼]

The quantitative detection of allergens in the food chain is a strategic health objective as the prevalence of allergy continues to rise. Food allergenicity is caused by proteins either in their native form or in forms resulting from food processing. Progress in mass spectrometry greatly opened up the field of proteomics. These advances are now available for the detection and the quantification of traces of allergenic proteins in complex mixtures, and complete the set of biological tests used until now, such as ELISA or PCR. We review methods classified according to their ability to simultaneously quantify and identify allergenic proteins and underline major advances in the mass-spectrometric methods. [less ▲]

Enhancement of steroid receptor-mediated transcription for the development of highly responsive bioassays

in Analytical and Bioanalytical Chemistry (2005), 382(4), 894-905

We have previously generated several transformed human mammary cell lines for the detection of steroid receptor-mediated activities and used these cell lines to detect and characterize steroid hormone ... [more ▼]

We have previously generated several transformed human mammary cell lines for the detection of steroid receptor-mediated activities and used these cell lines to detect and characterize steroid hormone (ant)agonistic compounds. In this report, we describe the specific optimization procedures used to enhance receptor-mediated transcription through the human glucocorticoid, progesterone and androgen receptors, respectively. Sodium arsenite-induced chemical stress leads to a substantial and specific increase in the glucocorticold receptor-mediated transcription, resulting in maximal stimulations of more than 2000-fold by the agonist dexamethasone. Similarly, a combined treatment with forskolin (an activator of adenylate cyclase) and trichostatin A (an inhibitor of histone deacetylases) leads to a synergistic enhancement of progesterone or androgen stimulation, resulting in a maximal induction of more than 200-fold or about 100-fold, respectively. The enhanced responses to specific steroids are mediated by the corresponding nuclear receptor. We show that by using these enhanced transcriptional stimulation protocols, it is possible to detect lower amounts of steroid hormones without substantially affecting the relative biological activities of various agonists. Finally, the application of these enhanced reporter cell assays to real biological samples from meat-producing animals is evaluated, and some validation parameters are presented. [less ▲]

Recombinant human estrogen, androgen and progesterone receptors for detection of potential endocrine disruptors

in Analytical and Bioanalytical Chemistry (2004), 378(3), 664-669

This work reports the binding capacity of various chemicals (so-called endocrine disruptors) to recombinant human steroid receptors (hERalpha, hPR and hAR). The tested chemicals are organochlorine ... [more ▼]

This work reports the binding capacity of various chemicals (so-called endocrine disruptors) to recombinant human steroid receptors (hERalpha, hPR and hAR). The tested chemicals are organochlorine insecticides (DDT and its metabolites, methoxychlor, aldrin, dieldrin, chlordecone, lindane, trichlorobenzene), estrogenic insecticides (endosulfan, toxaphene, nonachlor), herbicides (alachlor and atrazine), fungicides (benomyl and vinclozolin), industrial chemicals (nonylphenol, bisphenol A, diphenylphtalate), antioxidants (butylated hydroxyanisol) and some phytoestrogens. Except for phytoestrogens, most of the tested chemicals (DDT and its metabolites, aldrin, alpha- and beta-endosulfan, toxaphen, trans-nonachlor) show higher affinities for hPR than for hERalpha, indicating that the interaction with the progesterone receptor could contribute to the endocrine-disrupting effects imputed to these chemicals. We propose to use binding assays using recombinant human steroid receptors as screening tools for the detection of endocrine disruptors in various samples. [less ▲]

An improved clean-up strategy for simultaneous analysis of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and polychlorinated biphenyls (PCB) in fatty food samples

in Analytical and Bioanalytical Chemistry (2002), 372(2), 373-381

The study and extension of a simple automated clean-up method for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) to a broad range of polychlorinated biphenyls (PCB) is ... [more ▼]

The study and extension of a simple automated clean-up method for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) to a broad range of polychlorinated biphenyls (PCB) is described. The isolation of seven PCDD, ten PCDF, and three coplanar PCB (cPCB) is extended to eight monoortho substituted PCB and seven so-called "marker PCB" (Aroclor 1260) for fatty food samples. This enables quantification of 35 compounds - including all congeners with a WHO toxic equivalent factor (TEF)--in a single extraction and single purification step. The chromatographic behaviour of mono-ortho PCB and marker PCB on a variety of adsorbents, including basic alumina, has been studied. Partitioning of analytes through multi-column sequences is described and correlated with their structural and electronic properties, by use of molecular modelling calculations. The fractionation process available with the Power-Prep automated clean-up system enables rapid independent analysis of the different groups of compounds. Gas chromatography with high resolution mass spectrometry (GC-HRMS) is used for the PCDD/F and cPCB fraction and quadrupole ion-storage tandem in time mass spectrometry (GC-QISTMS) for analysis of the remaining PCB. A comparison study was performed on quality-control samples and real fatty food samples to evaluate the robustness of the new strategy compared with a reference method. On the basis of this simultaneous clean-up, a rapid simplified strategy for PCDD/F and selected PCB analysis determination is proposed for fatty food samples. [less ▲]