Disposable microfluidic ELISA for the rapid determination of folic acid content in food products

A micro-analytical system for rapid and quantitative analysis by inhibition immunoassay is presented and applied to the detection of folic acid. Eight polymer microchannels of 65-nL volume each and containing microelectrodes are embedded in a cartridge so that they can be operated simultaneously. All fluidic steps as well as the amperometric detection in the channels are operated by an instrument and software developed in-house. The fluidic steps of the immunoassay occur through hydrodynamic loading of the different solutions through the channels. The speed and duration of the flow and incubation parameters can thus be adapted to the biological and testing requirements. The effectiveness of the system was demonstrated by analysing folic acid concentrations in real infant formula samples within 5 min. In an effort to get a fully monitored assay, each fluidic step is monitored thanks to continuous amperometric detection of oxygen in the microchannel.