Small-angle optical deflection from collinear configuration for sensitive detection in microfluidic systems.
This paper describes a novel detection system based on small-angle optical deflection from the collinear configuration of a microfluidic chip. In this system, the incident light beam was focused on the microchannel through the edge of a lens, resulting in a small deflection angle that deviated 20° from the collinear configuration. The emitted fluorescence was collected through the center of the same lens and delivered to a photomultiplier tube in the vertical direction; the reflection light of the chip plate was kept away from the detector. In contrast to traditional confocal and nonconfocal laser-induced fluorescence detection systems, background levels resulting from scattered excitation light, reflection and refraction from the microchip was significantly eliminated. Significant enhancement of the signal-to-noise ratio was obtained by shaping a laser beam that combined an attenuator with a spectral filter to optimize laser power and the dimensions of the laser beam. FITC and FITC-labeled amino acid were used as model analytes to demonstrate the performance sensitivity, separation efficiency, and reproducibility of this detection system by using a hybrid polydimethylsiloxane/glass microfluidic device. The limit of detection of FITC was estimated to be 2 pM (0.55 zmol) (S/N = 3). Furthermore, the single cell analysis for the determination of intracellular glutathione in a single 3T3 mouse fibroblast cell was demonstrated. The results suggest that the proposed optical arrangements will be promising for development of sensitive, low-cost microfluidic systems.
College of Chemistry and College of Chemical Engineering, Sichuan University, Chengdu, P. R. China.
Li
L
Yang
Xiangtang
X
Li
Jing
J
Li
Hongyan
H
Yuan
Shulin
S
Zhao
Dan
D
Xiao
D000596:Amino Acids / Q000032:analysis / Q000737:chemistry; D000818:Animals; D004867:Equipment Design; D016650:Fluorescein-5-isothiocyanate / Q000032:analysis / Q000737:chemistry; D005978:Glutathione / Q000032:analysis / Q000737:chemistry; D042541:Intracellular Space / Q000737:chemistry; D051379:Mice; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D041681:NIH 3T3 Cells; D055095:Optics and Photonics / Q000295:instrumentation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods
D000596:Amino Acids; D005978:Glutathione; D016650:Fluorescein-5-isothiocyanate