Microfluidic immunoassays have demonstrated broad application to the detection and quantification of analytes ranging from small drug molecules to large proteins and biomolecules. These systems exhibit short length scales, reduced sample volumes, and precise manipulation, as well as exploit the sensitive and specific nature of antibody-antigen binding. Here we present the analytical investigation of a microfluidic homogeneous competitive immunoassay that incorporates antibody-conjugated superparamagnetic nanoparticles and magnetophoretic transport to enhance the limits of detection and dynamic range. The analytical model considers the advective, diffusive, and magnetophoretic transport of the antibody-coated nanoparticles relative to the labeled and sample antigens of interest in a T-sensor configuration. The magnetophoresis-diffusion immunoassay identified clear improvements to the assay response and reductions to the limit of detection for increased magnetophoretic velocities and larger nanoparticles. The externally applied magnetophoretic transport enriched the antibody-antigen accumulation region, while larger nanoparticles led to decreased diffusive peak broadening. The integration of nanoparticles to the diffusion immunoassay (NP-DIA) demonstrated an approximately 3-fold improvement to the limit of detection of the basic antibody/antigen system, while the integration of superparamagnetic nanoparticles and magnetophoretic transport (MIA) established an order of magnitude improvement. The implementation of an external force, i.e., magnetic, enabled the detectable antigen size spectrum to be extended up to large proteins and macromolecules. This investigation provides guidelines for the design and development of a magnetophoresis-diffusion T-sensor immunoassay, and clearly identifies the regimes for optimal operation.
Citation: Lab on A Chip
Pub Type: Journals
Microfluidics, Competitive Immunoassay, Magnetophoresis, T-Sensor, Immunomagnetic Nanoparticles