Determination of ethyl sulfate in human serum and urine by capillary zone electrophoresis

The use of capillary zone electrophoresis (CZE) with indirect absorbance detection for the analysis of ethyl sulfate (EtS) in serum and urine was investigated. EtS is a direct metabolite of ethanol employed as marker for recent alcohol consumption. Fused-silica capillaries of 60 cm total length were either coated with cetyltrimethylammonium bromide (CTAB, 50 microm I.D. capillary) or poly(diallyldimethylammonium chloride) (PDADMAC, 100 microm I.D. capillary) to allow CZE analyses to be performed with reversed polarity. At pH 2.2 with a maleic acid/phthalic acid background electrolyte, both approaches provided reliable EtS serum levels down to 0.2 mg L(-1) (1.6 microM) for the analysis of solid-phase extracts that were prepared after chloride precipitation. Analysis of urines diluted to a conductivity of 5 S m(-1) and analyzed in the two capillary formats resulted in limits of quantification (LOQs) of 2 and 1 mg L(-1), respectively. With urines adjusted to 10 S m(-1) via dilution or condensation, an LOQ of 0.6 mg L(-1) (4.8 microM) was obtained in the CTAB coated capillary whereas in the PDADMAC-coated capillary of equal length not all matrix components were resolved from EtS. The developed assays are robust and suitable to monitor EtS in samples of individuals who consumed as little as one standard drink of an alcoholic beverage containing about 14 g of ethanol.

Fluorescence-encoded gold nanoparticles: library design and modulation of cellular uptake into dendritic cells.

In order to harness the unique properties of nanoparticles for novel clinical applications and to modulate their uptake into specific immune cells we designed a new library of homo- and hetero-functional fluorescence-encoded gold nanoparticles (Au-NPs) using different poly(vinyl alcohol) and poly(ethylene glycol)-based polymers for particle coating and stabilization. The encoded particles were fully characterized by UV-Vis and fluorescence spectroscopy, zeta potential and dynamic light scattering. The uptake by human monocyte derived dendritic cells in vitro was studied by confocal laser scanning microscopy and quantified by fluorescence-activated cell sorting and inductively coupled plasma atomic emission spectroscopy. We show how the chemical modification of particle surfaces, for instance by attaching fluorescent dyes, can conceal fundamental particle properties and modulate cellular uptake. In order to mask the influence of fluorescent dyes on cellular uptake while still exploiting its fluorescence for detection, we have created hetero-functionalized Au-NPs, which again show typical particle dependent cellular interactions. Our study clearly prove that the thorough characterization of nanoparticles at each modification step in the engineering process is absolutely essential and that it can be necessary to make substantial adjustments of the particles in order to obtain reliable cellular uptake data, which truly reflects particle properties.