Electrochemistry-mass spectrometry unveils the formation of reactive triclocarban metabolites

Triclocarban (3,4,4'-trichlorocarbanilide, TCC) is a widely used antibacterial agent in personal care products and is frequently detected as an environmental pollutant in waste waters and surface waters. In this study, we report novel reactive metabolites potentially formed during biotransformation of TCC. The oxidative metabolism of TCC has been predicted using an electrochemical cell coupled online to liquid chromatography and electrospray ionization mass spectrometry. The electrochemical oxidation unveils the fact that hydroxylated metabolites of TCC may form reactive quinone imines. Moreover, a so-far unknown dechlorinated and hydroxylated TCC metabolite has been identified. The results were confirmed by in vitro studies with human and rat liver microsomes. The reactivity of the newly discovered quinone imines was demonstrated by their covalent binding to glutathione and macromolecules, using β-lactoglobulin A as a model protein. The results regarding the capability of the electrochemical cell to mimic the oxidative metabolism of TCC are discussed. Moreover, the occurrence of reactive metabolites is compared with findings from earlier in vivo studies and their relevance in vivo is argued.

Preferential binding of platelets to monocytes over neutrophils under flow

This study was undertaken to systematically investigate the binding kinetics of platelet recruitment by monocytes relative to neutrophils in bulk suspensions subjected to shear as well as the molecular requirements of leukocyte-platelet binding. Hydrodynamic shear-induced collisions augment the proportion of monocytes with adherent platelets more drastically than that of neutrophils with bound platelets. These heterotypic interactions are further potentiated by platelet activation with thrombin or to a lesser extent by monocyte stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP). Monocyte-platelet heteroaggregation increases with increasing shear rate and shear exposure time. Platelet P-selectin binding to monocyte P-selectin-glycoprotein-ligand-1 is solely responsible for maximal platelet adhesion to unstimulated monocytes in shear flow. However, the enhanced platelet binding to fMLP-treated monocytes involves a sequential two-step process, wherein P-selectin-PSGL-1 interactions are stabilized by CD18-integrin involvement. Blocking platelet alpha(IIb)beta(3) or monocyte beta(1)-integrin function had no effect. This study underscores the preferential recruitment of platelets by monocytes relative to neutrophils in shear flow, and demonstrates that the shear environment of the vasculature coupled to the state of cell activation modulates the dynamics and molecular constituents mediating monocyte-platelet adhesion.

Development of an ELISA for the detection of the residues of the insecticide imidacloprid in agricultural and environmental samples

A competitive enzyme-linked immunosorbent assay (ELISA) for the chloronicotinyl insecticide imidacloprid was developed using a polyclonal antibody produced against a hapten conjugated through the imidazolidine to keyhole limpet hemocyanin. In the standard curve of imidacloprid, an IC(50) of 17.3 ng/mL was obtained using a competitive heterologous system at pH 10. Very low cross-reactivity was found for some structurally related compounds including the insecticide thiacloprid. The high cross-reactivity with a metabolite containing the carbonyl group in the imidazolidine moiety suggests the involvement of its polarity and stereochemical fitness in forming the antibody--antigen complex. The effects of various assay conditions, including organic solvents, detergent content, salt concentration, and pH on the sensitivity were evaluated. High-performance liquid chromatography was run for comparison to validate the ELISA with fortified water samples, the correlation being 0.997-0.998 (n = 15) with a slope of 1.10--1.38. The ELISA turned out to be a convenient tool for monitoring imidacloprid residues in agricultural and environmental samples.