PNNL

Abstract

In this paper we describe a simple method for forming a renewable filter within a microfluidic system and demonstrate its use for capturing chemically selective beads that are too small to be easily captured in previous flow cells for renewable separation columns. The renewable filter is created by trapping larger beads in a flow cell. Smaller beads are then captured either within or on top of the bed of larger beads. A renewable filter created with 19.9 um beads was used to trap 5.6 um optically encoded beads in a sequential injection renewable separation column (SI-RSC). Both the selective microspheres and filter bed are automatically emplaced and discarded for each sample. Small (5.6 um) bead trapping efficiency in the SI-RSC was 99%. The use of the renewable filter in combination with flow cytometry fluorescence detection was demonstrated with model one-step and two-step assays, and the multiplexed detection of two analytes using optically encoded beads. The larger beads forming the renewable filter did not interfere with 5.6 um bead detection in the flow cytometer. The bead injection method described here provides a general platform for coupling renewable surface methods for sample preparation and analyte labeling with flow detectors for multiplexed analyses.