ABSTRACT
This article presents a magnetically actuated two-way, three-position (+, 0, -), paper-based microfluidic valve that includes a neutral position (0)-the first of its kind. The system is highly robust, customizable, and fully automated. The advent of a neutral position and the ability to precisely control switching frequencies establish a new platform for highly controlled fluid flows in paper-based wicking microfluidic devices. The potential utility of these valves is demonstrated in automated, programmed, patterning of dyed liquids in a wicking device akin to a colorimetric assay but with a programmed fluid/reagent delivery. These valves are fabricated using facile methods and thus remain cost-effective for adoption into affordable point-of-care/bioanalytical devices.
ABSTRACT
AIM: We present a fast magnetic immunoassay, combining magnetic nanoparticles and micromagnets. High magnetic field gradients from micromagnets are used to develop a new approach to the standard ELISA. Materials & methods/results: A proof-of-concept based on colorimetric quantification of antiovalbumin antibody in buffer is performed and compared with an ELISA. After optimization, the magnetic immunoassay exhibits a limit of detection (40 ng/ml) and a dynamic range (40-2500 ng/ml) similar to that of ELISAs developed using same biochemical tools. CONCLUSION: Micromagnets can be fully integrated in multiwell plates at low cost to allow the efficient capture of immunocomplexes carried by magnetic nanoparticles. The method is generic and permits to perform magnetic ELISA in 30 min.
