Ultrasensitive Cross-Correlation Electrophoresis on Microchip Devices

Abstract

Cross-correlation electrophoresis with fluorescence detection on a microchip device was used to resolve a mixture of 63 pM fluorescein and 70 pM dichlorofluorescein. The signal-to-noise ratios of analyte peaks in a correlogram derived from a 9-bit pseudorandom injection sequence were ∼17 for dichlorofluorescein and ∼6 for fluorescein. In contrast, neither peak was detected in a conventional electropherogram obtained on the microchip. Detection limits estimated from a correlogram derived from the average of 12 7-bit correlograms were 6.5 pM dichlorofluorescein and 21 pM fluorescein. These are the lowest detection limits reported for a microchip separation device using analog detection and the first example of cross-correlation electrophoresis on a monolithic device. The small injection volumes, injection reproducibility, and rapid separations enabled by microchip devices make cross-correlation multiplex injection schemes a viable approach for achieving enhanced sensitivity.

Peer Reviewed: Hadamard Transform CE

“…Electrokinetic injection is one of the methods that can be used to randomly inject the sample and buffer solution. For example, this multiplex injection method has been demonstrated with cross-correlation CE using microchip technology (3,4). In addition, electrokinetic injection can be applied to several detection methods-absorbance, conventional fluorescence, and electrochemical.…”

Detection of immunoglobulins in a laser induced fluorescence system utilizing polydimethysiloxane microchips with advanced surface and optical properties

“…The procedure of result evaluation is also automated. If we compare our LIF system to similar reported detectors, 11,[13][14][15]18 we expect similar investment cost. On the other hand, we believe that the developed LIF detector in combination with the used PDMS microfluidic chip favors our system among others due to at least two reasons: ͑i͒ the developed PDMS microfluidic chip avoids the traditional use of expensive silicon stamps and oxygen plasma treatment and ͑ii͒ the exploited polyelectrolyte layer ͑PEL͒ technique of receptor immobilization significantly improves the intensity and homogeneity of the obtained fluorescence signals and can be, in principle, used in many heterogeneous sandwich immunoassays because immunoglobulins and other proteins can be successfully immobilized in this way.…”

“…A detection limit of 0.12 pM FITC was obtained. A LIF system was also used by Fister et al, 14 who studied electrophoretic separation of dilute dye solutions. The obtained detection limits were 6.5 pM dichlorofluorescein and 21 pM fluorescein.…”

Electrochemical and optical detectors for capillary and chip separations

“…As a result, non-confocal optical arrangements, including bevel-incident laser and orthogonal optical arrangements, are used; in these, the interference from the excitation light to emitted fluorescence was eliminated. In a bevel-incident laser system [57][58][59][60][61][62], as shown in Fig. 9(b and c), the laser beam was positioned to minimize scatter while the fluorescence was detected perpendicular to the chip.…”