Development of a Multichannel Microfluidic Analysis System Employing Affinity Capillary Electrophoresis for Immunoassay

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Abstract
A six-channel microfluidic immunoassay device with a scanned fluorescence detection system is described. Six independent mixing, reaction, and separation manifolds are integrated within one microfluidic wafer, along with two optical alignment channels. The manifolds are operated simultaneously and data are acquired using a single-point fluorescence detector with a galvano-scanner to step between separation channels. A detection limit of 30 pM was obtained for fluorescein with the scanning detector, using a 7.1-Hz sampling rate for each of the reaction manifolds and alignment channels (57-Hz overall sampling rate). Simultaneous direct immunoassays for ovalbumin and for anti-estradiol were performed within the microfluidic device. Mixing, reaction, and separation could be performed within 60 s in all cases and within 30 s under optimized conditions. Simultaneous calibration and analysis could be performed with calibrant in several manifolds and sample in the other manifolds, allowing a complete immunoassay to be run within 30 s. Careful chip conditioning with methanol, water, and 0.1 M NaOH resulted in peak height RSD values of 3−8% (N = 5 or 6), allowing for cross-channel calibration. The limit of detection (LOD) for an anti-estradial assay obtained in any single channel was 4.3 nM. The LOD for the cross-channel calibration was 6.4 nM. Factors influencing chip and detection system design and performance are discussed in detail.