01964nas a2200325   4500008004100000022001400041245004900055210004500104260001300149300001000162490000700172520109000179653002501269653002901294653002501323653001401348653004201362653001601404653002101420653001401441653001301455100001301468700001801481700001801499700001701517700002001534700001601554700001301570856005501583       2001                        eng d  a1087-015600aA rapid diffusion immunoassay in a T-sensor.0 arapid diffusion immunoassay in a Tsensor  c2001 May  a461-50 v193 a<p>We have developed a rapid diffusion immunoassay that allows measurement of small molecules down to subnanomolar concentrations in <1 min. This competitive assay is based on measuring the distribution of a labeled probe molecule after it diffuses for a short time from one region into another region containing antigen-specific antibodies. The assay was demonstrated in the T-sensor, a simple microfluidic device that places two fluid streams in contact and allows interdiffusion of their components. The model analyte was phenytoin, a typical small drug molecule. Clinically relevant levels were measured in blood diluted from 10- to 400-fold in buffer containing the labeled antigen. Removal of cells from blood samples was not necessary. This assay compared favorably with fluorescence polarization immunoassay (FPIA) measurements. Numerical simulations agree well with experimental results and provide insight for predicting assay performance and limitations. The assay is homogeneous, requires <1 microl of reagents and sample, and is applicable to a wide range of analytes.</p>10aAntibody Specificity10aAntigen-Antibody Complex10aBinding, Competitive10aDiffusion10aFluorescence Polarization Immunoassay10aImmunoassay10aMolecular Weight10aPhenytoin10aRheology1 aHatch, A1 aKamholz, A, E1 aHawkins, K, R1 aMunson, M, S1 aSchilling, E, A1 aWeigl, B, H1 aYager, P  uhttp://microfluidicsciences.com/drupal/?q=node/22801747nas a2200217   4500008004100000022001400041245009200055210006900147260001500216300001100231490000700242520109300249653001301342653002101355653003101376100001801407700001601425700002001441700001301461856005501474       1999                        eng d  a0003-270000aQuantitative analysis of molecular interaction in a microfluidic channel: the T-sensor.0 aQuantitative analysis of molecular interaction in a microfluidic  c1999 Dec 1  a5340-70 v713 a<p>The T-sensor is a recently developed microfluidic chemical measurement device that exploits the low Reynolds number flow conditions in microfabricated channels. The interdiffusion and resulting chemical interaction of components from two or more input fluid streams can be monitored optically, allowing measurement of analyte concentrations on a continuous basis. In a simple form of T-sensor, the concentration of a target analyte is determined by measuring fluorescence intensity in a region where the analyte and a fluorescent indicator have interdiffused. An analytical model has been developed that predicts device behavior from the diffusion coefficients of the analyte, indicator, and analyte--indicator complex and from the kinetics of the complex formation. Diffusion coefficients depend on the local viscosity which, in turn, depends on local concentrations of all analytes. These relationships, as well as reaction equilibria, are often unknown. A rapid method for determining these unknown parameters by interpreting T-sensor experiments through the model is presented.</p>10aKinetics10aModels, Chemical10aSpectrometry, Fluorescence1 aKamholz, A, E1 aWeigl, B, H1 aFinlayson, B, A1 aYager, P  uhttp://microfluidicsciences.com/drupal/?q=node/229