Microchip systems for immunoassay: an integrated immunoreactor with electrophoretic separation for serum theophylline determination

Abstract

A glass microchip is described in which reagents and serum samples for competitive immunoassay of serum theophylline can be mixed, reacted, separated, and analyzed. The device functions as an automated microfluidic immunoassay system, creating a lab-on-a-chip. Electroosmotic pumping was used to control first the mixing of 50-fold-diluted serum sample with labeled theophylline tracer in a 1:1 ratio, followed by 1:1 mixing and reaction with anti-theophylline antibody. The 51-nL on-chip mixer gave the same concentration as dilution performed off-chip, within 3%. A 100-pL plug of the reacted solution was then injected into an electrophoresis separation channel integrated within the same chip. Measurements of free and bound tracer by fluorescence detection gave linear calibration curves of signal vs log[theophylline] between 0 and 40 mg/L, with a slope of 0.52 ± 0.03 and an intercept of −0.04 ± 0.04 after a 90-s reaction time. A detection limit of 0.26 mg/L in serum (expressed before the dilution step, actual concentration of 1.3 μg/L at the detector) was obtained. Recovery values were 107% ± 8% for 15 mg/L serum samples.

Electrohydrodynamic mixing in microchannels

“…. Chiem and Harrison, 1998 . The ability to manipulate reagents and reaction products ''on-chip'' suggests the eventual ability to perform virtually any type of '' wet-chemical'' process on a microfabricated device consisting of several microchannels.…”

Clinical applications of capillary electrophoresis based immunoassays

“…Another area that has seen a variety of applications of CEbased immunoassays is in the determination of drugs in clinical samples. This work has included the development of these assays for toxicology, therapeutic drug monitoring, forensic analysis, and screening assays for drugs of abuse [26,34,61,75,[107][108][109][110][111][112][113][114][115][116]. As is shown in Table 2, most of these methods have again involved the use of a homogeneous competitive binding immunoassay and fluorescence detection.…”

Sample Pretreatment and Nucleic Acid-Based Detection for Fast Diagnosis Utilizing Microfluidic Systems

“…In the past decade, bio-MEMS technology has been used to miniaturize biomedical devices and systems. 16,49,110,120,158 A microchip fabricated using this technology is usually referred to as a ''lab-on-a-chip'' (LOC) or a micro-total-analysis-system (micro-TAS). The LOC or micro-TAS can perform the basic functions of sample preparation, mixing, reaction, transport, collection, separation, and detection on a single chip automatically.…”