Flow-Based Microimmunoassay

Abstract

A small-volume heterogeneous immunoassay system is demonstrated in microchannels exploiting magnetic manipulations of small paramagnetic particles (1-2-microm diameter). The small-diameter particles help to create a high surface-area-to-volume ratio that generates the sensitivity for the small detection volumes. Flow characteristics of the magnetically formed packed bed within the channel allow the assay to be carried out quickly (minutes) while passing appropriate volumes of both samples and reagents (microliters to hundreds of nanoliters) through the system. The assay is demonstrated with a direct interaction of fluorescein isothiocyanate (FITC) with an immobilized anti-FITC conjugate in which a small-volume sample (< 1 microL) reaches 90% of maximum signal in 3 min. Heterogeneous sandwich assays are demonstrated with parathyroid hormone (PTH) and interleukin-5 (IL-5). Both the PTH assay and IL-5 assays were carried out on microliter volumes and demonstrated physiologically relevant sensitivity (approximately microg/L).

Magnetic bead handling on-chip: new opportunities for analytical applications

“…In another study, a small-volume heterogeneous immuno-assay was demonstrated using both classical fused-silica capillaries and glass microfluidic chips (Hayes et al 2001b). Figure 5 is a schematic diagram of the experimental configuration.…”

PEGylation of magnetic poly(glycidyl methacrylate) microparticles for microfluidic bioassays

“…The boom in microfluidics, which began about 20 years ago, brought with it ideas about incorporating magnetic particles into various microfluidic devices [6][7][8][9] . This offers additional benefits compared to batchtype processes, such as reduced sample and reagent volumes, faster reaction times, the possibility to engineer the design of a chip to control particle mobility, and integration of various processes into a unified system 5 .…”

Numerical investigation of flow-through immunoassay in a microchannel

“…8 The initial feasibility studies [9][10][11] in this regard have been mostly empirical 12 and there are few comprehensive models available that describe the interaction between target species and magnetic particles. 5 We therefore conduct a fundamental investigation of the mechanics of magnetic separation on a microfluidic platform using threedimensional numerical simulations.…”