Urine toxicological screening method using an immunoenzymatic assay based on a biochip array technology: comparative study with immunochromatography and Liquid chromatography­mass spectrometry / Criblage toxicologique urinaire par une méthode automatisée immunoenzymatique multiparamétrique basée sur une technique de biopuce : comparaison à de l'immunochromatographie et de la chromatographie liquide couplée à de la spectrométrie de masse

Multiparametric toxicology research is mainly based on immunochromatography [IC] and chromatography methods. A new automated method using an immunoenzymatic (IE) assay based on a biochip array technology combines short turning around time and analytical performances close to chromatography in terms of positivity cut-off. The aim of our study was to compare IE versus IC and chromatography methods using urines samples from clinical cases. Seventy-two samples were analyzed by IC (amphetamines, opiates, benzodiazepines, THC, methadone, cocaine), IE and chromatography (previous classes plus opioids and cathinone). Immunochromatography results were read by at least 7 operators to assess reading subjectivity. Immunoenzymatic, IC, and chromatrography results were compared with each other. Chromatographic quantification was analyzed to understand discrepancies. Significant discrepancies (29-64%) were observed between IC and IE for most of the drug families investigated except for benzodiazepines, methadone and opiates. These discrepancies were not identified between IE and chromatography, except for some substances (28% to 67% discrepancies for buprenorphine, tramadol and oxycodone, 100% for cathinone). In contrast to IC, the performance of IE approached those of chromatography, except for some substances for which cross-reactions must be investigated. Reading discrepancies were frequent with IC (33% of samples) and made robust result output challenging. In conclusion, the Multistat® is an interesting method for first-line toxicological screening for laboratories without chromatography method.

La recherche des toxiques multiparamétrique repose principalement sur des méthodes immunochromatographie [IC] et de chromatographie (CL). Une nouvelle méthode automatisée immunoenzymatique (IE) (Multistat®) en biopuce, combine un rendu de résultats rapide et des performances analytiques, en termes de seuils de positivité, proche de la CL. L'objectif de notre étude a été de comparer l'IE à des méthodes d'IC et de CL sur des échantillons hospitaliers. Soixante-douze échantillons ont été analysés par IC (amphétamines, opiacés, benzodiazépines, THC, méthadone, cocaïne), IE et CL (classes précédentes plus opioïdes et dérivés de la cathinone). Les résultats d'IC étaient lus par au moins 7 personnes pour évaluer la subjectivité des lectures. Les résultats d'IE, d'IC et de CL étaient comparés entre eux. La quantification en CL était exploitée pour expliquer les discordances. Une forte proportion de discordances (de 29 à 64 %) était observée entre IC et IE sur la plupart des toxiques explorées sauf pour les benzodiazépines, la méthadone et les opiacés. Ces discordances n'étaient pas retrouvées entre IE et CL, hormis pour certaines substances (28 % à 67 % de divergences pour buprénorphine, tramadol et oxycodone, 100 % pour les dérivés de la cathinone). À l'inverse de l'IC, les performances de l'IE se rapprochaient de celles de la CL, sauf pour certaines substances pour lesquelles des réactions croisées doivent être recherchées. Les discordances de lecture étaient fréquentes en IC et rendent difficile un rendu de résultat robuste. En conclusion, le Multistat® est une méthode intéressante pour un criblage en première intention pour les laboratoires sans CL.

Interfacial and Bulk Stabilization of Oil/Water System: A Novel Synergistic Approach.

Oil/water emulsions are usually stabilized either by interfacial modification using nanoparticles and surfactants (stated as pickering emulsion or bijels) or by bulk stabilization with the help of low-molecular-weight or polymeric gelators (known as bigels) in response to some external stimuli (e.g., pH, temperature). Both these approaches result in different systems that are quite useful for different applications, including catalysis, pharmaceutical and agrochemicals. However, these systems also possess some inherent drawbacks that need to be addressed, like difficulty in fabrication and ensuring the permanent binding of nanoparticles at the oil/water interface, in case of nanoparticles stabilized emulsions (i.e., interfacial stabilization). Similarly, the long-term stability of the oil/water systems produced by using (hydro/organo) gelators (i.e., bulk stabilization) is a major concern. Here, we show that the oil/water system with improved mechanical and structural properties can be prepared with the synergistic effect of interfacial and bulk stabilization. We achieve this by using nanoparticles to stabilize the oil/water interface and polymeric gelators to stabilize the bulk phases (oil and water). Furthermore, the proposed strategy is extremely adaptable, as the properties of the resultant system can be finely tuned by manipulating different parameters such as nanoparticles content and their surface functionalization, solvent type and its volume fraction, and type and amount of polymeric gelators.

Compensating for Electrode Polarization in Dielectric Spectroscopy Studies of Colloidal Suspensions: Theoretical Assessment of Existing Methods.

Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP). In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical) with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed.