Chemiluminescence (CL) detection integrated with a microchip capillary electrophoresis (MCE) system that was fabricated in poly(dimethylsiloxane) was demonstrated for chemical and biochemical analyses. Two model CL systems were involved here: metal ion-catalyzed luminol-peroxide reaction and dansyl species conjugated peroxalate-peroxide reaction. Different strategies based on three chip patterns (cross, cross combining with Y, and cross combining with V) to perform on-line CL detection for MCE were evaluated and compared in terms of sensitivity, reproducibility, and peak symmetry. The chip pattern of cross combining with Y proved to be promising for the luminol-peroxide CL system, while the chip pattern of cross combining with V was preferred for the peroxalate-peroxide system where CL reagent could not be effectively transported by electroosmotic flow. A detection limit down to submicromolar concentrations (midattomole) was achieved with good reproducibility and symmetric peak shape. Successful separation of three metal cations such as Cr(III), Co(II), and Cu(II) and chiral recognition of dansyl phenylalanine enantiomers within 1 min revealed distinct advantages of combining MCE with CL detection for rapid and sensitive analyses.

In this article, a microfluidic platform integrating capillary electrophoresis and bioluminescence (BL) detection that was fabricated in poly(dimethylsiloxane) (PDMS) with lab-on-a-chip technology was demonstrated for cellular metabolic analyses. A microchannels network, "cross combining with Y", was designed to perform on-chip sample preparation, separation, and BL detection of ATP and ATP-conjugated metabolites, using firefly luciferin-luciferase BL system. A dynamic modification of the channel wall of PDMS proved to be crucial to reverse the direction of electroosmotic flow (EOF), which was uniquely achieved by a prewash cycle with a cationic surfactant didodecyldimethylammonium bromide. The influences of surfactant on the EOF and BL reaction were also investigated. Quantitative analyses revealed a dynamic linear range over 2 orders of magnitude for ATP, with a detection limit down to submicromolar (midattomole). The method was validated by measuring cellular ATP of E. coli. with direct on-chip cell lysis. Further work was emphasized on ATP-conjugated metabolite analysis, using galactose as an example. Assays of galactose in human urine samples confirmed the reliability of the protocol, which revealed good prospect of this platform for ATP-conjugated submetabolomic profiling.

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We demonstrated surface-enhanced Raman spectroscopy using a coffee-ring-type three-dimensional silver nanostructure (Ag3D).