Modeling of a competitive microfluidic heterogeneous immunoassay: sensitivity of the assay response to varying system parameters.

We present a fractional sensitivity analysis of a competitive microfluidic heterogeneous immunoassay for a small molecule analyte. A simple two-dimensional finite element model is used to determine the fractional sensitivity of the assay signal with respect to analyte concentration, flow rate, initial surface density of binding sites, and antibody concentration. The fractional sensitivity analysis can be used to identify (1) the system parameters for which it is most crucial to control or quantify the variability between assays and (2) operating ranges for these parameters that improve assay sensitivity (within the constraints of the experimental system).

Experimental and model investigation of the time-dependent 2-dimensional distribution of binding in a herringbone microchannel.

A microfluidic device known to mix bulk solutions, the herringbone microchannel, was incorporated into a surface-binding assay to determine if the recirculation of solution altered the binding of a model protein (streptavidin) to the surface. Streptavidin solutions were pumped over surfaces functionalized with its ligand, biotin, and the binding of streptavidin to those surfaces was monitored using surface plasmon resonance imaging. Surface binding was compared between a straight microchannel and herringbone microchannels in which the chevrons were oriented with and against the flow direction.

Microcontact printed antibodies on gold surfaces: function, uniformity, and silicone contamination.

The function of microcontact printed protein was investigated using surface plasmon resonance (SPR) imaging, X-ray photoelectron spectroscopy spectroscopy (XPS), and XPS imaging. We chose to analyze a model protein system, the binding of an antibody from solution to a microcontact printed protein antigen immobilized to a gold surface. SPR imaging experiments indicated that the microcontact printed protein antigen was less homogeneous, had increased nonspecific binding, and bound less antibody than substrates to which the protein antigen had been physically adsorbed.

Concentration gradient immunoassay. 2. Computational modeling for analysis and optimization.

A novel microfluidic surface-based competition immunoassay, termed the concentration gradient immunoassay (described in detail in a companion paper (Nelson, K.; Foley, J.; Yager, P.

Concentration gradient immunoassay. 1. An immunoassay based on interdiffusion and surface binding in a microchannel.

We describe a novel microfluidic immunoassay method based on the diffusion of a small-molecule analyte into a parallel-flowing stream containing a cognate antibody. This interdiffusion results in a steady-state gradient of antibody binding site occupancy transverse to convective flow. In contrast to the diffusion immunoassay (Hatch, A.