MESIA: Magnetic force-assisted electrochemical sandwich immunoassays for quantification of prostate-specific antigen in human serum.

We propose a new immunoassay technique, called magnetic-force assisted electrochemical sandwich immunoassay (MESIA), where serum biomarkers can be determined by magnetic actuation and electrochemical detection of gold-coated iron oxide nanoparticles as probes for immunocomplex formation. In MESIA, neither washing buffer nor fluidic parts are necessary, because the formation of immunocomplexes and the removal of unbound probes are controlled by magnetic forces. Electrochemical pretreatment and measurement of the gold-coated magnetic probes allows highly sensitive, precise, and robust system for quantification of target analytes. Using MESIA, the concentration of prostate-specific antigen (PSA) in 10 µl of human serum is determined within 5 min. The limit of detection is 0.085 ng/mL, and the average coefficient of variance is 8.85% for five different PSA concentrations ranging from 0 to 25 ng/mL. This method shows good precision and reproducibility (<10%) and high correlation with cobas e 801 (r = 0.997) for clinical patient samples. We believe this technique to be useful in the development of a point-of-care testing platform for diagnosis and prognosis of various diseases, such as cancer, based on quantification of biomarkers in a drop of blood.

Effects of dimyristoylphosphatidylethanol and ethanol on thickness of neuronal membrane lipid bilayers.

The aim of this study was to provide a basis for examining the molecular mechanism for the pharmacological action of ethanol. Energy transfer between the surface fluorescent probe 1-anilinonaphthalene-8-sulfonic acid and hydrophobic fluorescent probe 1,3-di(1-pyrenyl)propane was used to examine the effect of both dimyristoylphosphatidylethanol (DMPEt) and ethanol on the thickness (D) of the synaptosomal plasma membrane vesicles (SPMV) isolated from the bovine cerebral cortex. The thickness (D) of the intact SPMV was 1.044 +/- 0.008 (arbitrary units, n=5) at 37 degrees C (pH 7.4). Both DMPEt and ethanol decreased the thickness of the SPMV lipid bilayer in a dose-dependent manner with a significant decrease in thickness observed at 5 microM and 25 mM, respectively. It was assumed that both ethanol and DMPEt cause interdigitation in the SPMV lipid bilayers. The effects of ethanol on the neuronal membranes were attributed to its direct and indirect actions. The indirect action of ethanol refers to the action of phosphatidylethanol, which is an ethanol abnormal metabolite, on the neuronal membranes. The decrease in membrane thickness by both DMPEt and ethanol might be responsible for some, but not all of its anesthetic actions.