No abstract

A new method for DNA diagnostics based on template-directed primer extension and detection by fluorescence polarization is described. In this method, amplified genomic DNA containing a polymorphic locus is incubated with oligonucleotide primers (designed to hybridize to the DNA template adjacent to the polymorphic site) in the presence of allele-specific dye-labeled dideoxyribonucleoside triphosphates and a commercially available modified Taq DNA polymerase. The primer is extended by the dye-terminator specific for the allele present on the template, increasing ∼10-fold the molecular weight of the fluorophore. At the end of the reaction, the fluorescence polarization of the two dye-terminators in the reaction mixture are analyzed directly without separation or purification. This homogeneous DNA diagnostic method is shown to be highly sensitive and specific and is suitable for automated genotyping of large number of samples.[The data shown in Figure 3 are available as an online supplement at http://www.genome.org.]

A novel microfluidic paper-based analytical device (μPAD) utilizing a nitrocellulose (NC) membrane to detect IgG antibodies through a colorimetric analysis is described. The μPAD was constructed using layered polyethylene terephthalate (PET) and pressure-sensitive adhesives (PSA). The biotin labeled Goat Anti-Mouse IgG antibody was spotted and dried on the NC channel prior to subjecting it to a series of wash solutions (Tris-tween), increasing concentrations of alkaline phosphatase conjugated to streptavidin (Strep-ALP), and para-nitrophenyl phosphate (p-NPP) realizing a vibrant yellow color. The reaction proceeds for 10 min before applying the p-NPP stop solution. The device was then dried, scanned, and analyzed yielding a linear range of inverse yellow color intensities versus Strep-ALP concentrations. The development of this simple μPAD should further facilitate the use of NC in colorimetric assays to detect and quantitate antibodies.

A novel microfluidic device was designed and developed to miniaturize, multiplex, and automate serial dilution and three-reagent dose-response assays using submicroliter quantities of reagents. This prototype microfluidic device can be used to measure enzyme kinetics and to test a chemical lead's response to a target by fluorescent readout using common plate readers and detection systems. The prototype microfluidic system yielded serial dilution and dose-response assay data comparable to results obtained from manual titrations and reagent additions performed using a microwell plate. Enzyme kinetics were highly reproducible using these devices, although Michaelis-Menten kinetics results differed from those obtained in the microwell plate. In all cases reported here, assays performed on the microfluidic format required lower volumes of reagents compared with the microwell plate. In addition to savings in reagent consumption, the microfluidic devices and bench-top instruments offer additional advantages over conventional solutions, including a small footprint and compatibility with commercially available fluorescence detectors. Future directions for the prototype technology are discussed.

Reported here are laminated membrane electrodes, an improved design and more advantageous method of fabrication for previously reported thin layer cell electrode systems developed on track‐etch membranes. The laminated membrane approach potentially further improves flow resistance by dramatically reducing the surface area to volume ratio, but also produces a cohesive device that can be more readily applied to a broad range of applications. In addition, this new fabrication method was implemented in a scalable, commercial process and resulting product demonstrations indicate that volume manufacturing is feasible. Characterization of laminated membrane electrodes reveal redox cycling amplification factors as high as 30 with linear responses to variable concentrations of redox couple. These performance characteristics are shown to be comparable to similar generator‐collector systems fabricated through much more laborious laboratory methods. This combination of added versatility, cost‐reduced fabrication and exceptional performance clearly reveals unrealized potential of track‐etch membrane approaches and boosts their candidacy as powerful new options for generator‐collector electrode systems.