title: Heterogeneous immunoassays in microfluidic format using fluorescence detection with integrated amorphous silicon photodiodes.
abstract: Miniaturization of immunoassays through microfluidic technology has the potential to decrease the time and the quantity of reactants required for analysis, together with the potential of achieving multiplexing and portability. A lab-on-chip system incorporating a thin-film amorphous silicon (a-Si:H) photodiode microfabricated on a glass substrate with a thin-film amorphous silicon-carbon alloy directly deposited above the photodiode and acting as a fluorescence filter is integrated with a polydimethylsiloxane-based microfluidic network for the direct detection of antibody-antigen molecular recognition reactions using fluorescence. The model immunoassay used consists of primary antibody adsorption to the microchannel walls followed by its recognition by a secondary antibody labeled with a fluorescent quantum-dot tag. The conditions for the flow-through analysis in the microfluidic format were defined and the total assay time was 30 min. Specific molecular recognition was quantitatively detected. The measurements made with the a-Si:H photodiode are consistent with that obtained with a fluorescence microscope and both show a linear dependence on the antibody concentration in the nanomolar-micromolar range.
authors.forename: A T
authors.initials: AT
authors.lastname: Pereira
authors.forename: P
authors.initials: P
authors.lastname: Novo
authors.forename: D M F
authors.initials: DM
authors.lastname: Prazeres
authors.forename: V
authors.initials: V
authors.lastname: Chu
authors.forename: J P
authors.initials: JP
authors.lastname: Conde