01969nas a2200325   4500008004100000022001400041245004900055210004500104260001300149300001000162490000700172520109000179653002501269653002901294653002501323653001401348653004201362653001601404653002101420653001401441653001301455100001301468700001801481700001801499700001701517700002001534700001601554700001301570856006001583       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  uhttps://www.microfluidicsciences.com/drupal/?q=node/22801752nas a2200217   4500008004100000022001400041245009200055210006900147260001500216300001100231490000700242520109300249653001301342653002101355653003101376100001801407700001601425700002001441700001301461856006001474       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  uhttps://www.microfluidicsciences.com/drupal/?q=node/22902105nas a2200313   4500008004100000022001400041245010800055210006900163260001600232300001100248490000900259520118500268653001101453653003901464653001801503653001901521653001801540653001001558653001701568653001401585653002101599653002501620653002601645100001401671700001901685700001501704700001301719856005901732       1998                        eng d  a0006-300200aFormation of high axial ratio microstructures from peptides modified with glutamic acid dialkyl amides.0 aFormation of high axial ratio microstructures from peptides modi  c1998 May 28  a168-840 v13713 a<p>A growing number of amphiphiles are known to form high axial ratio microstructures (HARMs) such as the hollow cylindrical microstructures called lipid tubules. As a prelude to exploring the potential of HARMs formed from lipopeptides in controlled release drug delivery, several microstructure formation conditions were investigated. We report the preparation of several glutamic acid dialkyl amides with varying alkyl chain lengths bearing a verity of peptides (1-4 amino acids) [peptide-Glu-(NHCnH2n+1)2, n=12, 14, 16]. These surfactants have been rapidly and efficiently converted into HARMs in aqueous buffer at physiological pH and ionic strength, or in buffer containing MeOH or EtOH. Helical ribbons and tubular HARMs were produced that were stable for as long as 6 months below the phase transition temperatures of the compounds. To estimate the stability of HARMs in vivo, HARMs formed from (Pro)3-Glu(NHC16H33)2 were incubated with DOPC liposomes or fetal calf serum at 40 degreesC. HARM size and shape did not change significantly, suggesting that such lipopeptide particles can retain their morphology long enough in vivo to be useful as drug delivery vehicles.</p>10aAmides10aCalorimetry, Differential Scanning10aDrug Carriers10aDrug Stability10aGlutamic Acid10aLight10aLipoproteins10aLiposomes10aPeptides, Cyclic10aPhosphatidylcholines10aScattering, Radiation1 aLee, K, C1 aLukyanov, A, N1 aGelb, M, H1 aYager, P  uhttps://www.microfluidicsciences.com/drupal/?q=node/3102393nas a2200289   4500008004100000022001400041245009200055210006900147260001500216300001000231490000700241520154100248653001101789653001601800653003901816653001401855653003201869653001601901653002401917653001801941100002001959700001901979700001801998700001302016700001502029856005902044       1997                        eng d  a0009-308400aFormation of high-axial-ratio-microstructures from natural and synthetic sphingolipids.0 aFormation of highaxialratiomicrostructures from natural and synt  c1997 Aug 8  a21-360 v883 a<p>Amphiphiles that form high-axial-ratio-microstructures (HARMs) are being considered as novel materials for controlled release of drugs and other biologically functional molecules. HARMs consisting of tubules, ribbons, solid rods and helices are formed from sphingolipids by addition of water to a solution of amphiphile in DMF. Single molecular species of galactocerebroside (GalCer) containing long unsaturated fatty acid chains or natural GalCer containing mixed-length, non-hydroxy fatty acids (NFA-GalCer) or alpha-hydroxy fatty acids (HFA-GalCer) form cylindrical structures. In contrast, single molecular species of GalCer containing long saturated fatty acids form ribbons and helices. GalCer HARMs are typically under 100 nm in diameter and have lengths of several microns. The importance of the amide of GalCer for HARM formation was evaluated using psychosine, which forms solid fibers, whereas sphingosine and an analog of GalCer in which the amide is reduced to a secondary amine form amorphous aggregates. Single molecular species of ceramide containing long unsaturated fatty acid chains form cylindrical structures, whereas those with long saturated fatty acids form ribbons and helices. Short chain saturated ceramide also forms cylindrical structures. GalCer analogs with N-acetyl-glycine in place of the galactose form fibers whereas those with N-acetyl-proline yield amorphous material. The N-acetyl-proline-containing amphiphile can de doped into pure GalCer or NFA-GalCer without perturbing tubule formation.</p>10aAmides10aAmino Acids10aCalorimetry, Differential Scanning10aCeramides10aDelayed-Action Preparations10aFatty Acids10aGalactosylceramides10aSphingolipids1 aGoldstein, A, S1 aLukyanov, A, N1 aCarlson, P, A1 aYager, P1 aGelb, M, H  uhttps://www.microfluidicsciences.com/drupal/?q=node/32