Microchip separations of protein biotoxins using an integrated hand-held device

Abstract

We report the development of a hand-held instrument capable of performing two simultaneous microchip separations (gel and zone electrophoresis), and demonstrate this instrument for the detection of protein biotoxins. Two orthogonal analysis methods are chosen over a single method in order to improve the probability of positive identification of the biotoxin in an unknown mixture. Separations are performed on a single fused-silica wafer containing two separation channels. The chip is housed in a microfluidic manifold that utilizes o-ring sealed fittings to enable facile and reproducible fluidic connection to the chip. Sample is introduced by syringe injection into a septum-sealed port on the device exterior that connects to a sample loop etched onto the chip. Detection of low nanomolar concentrations of fluorescamine-labeled proteins is achieved using a miniaturized laser-induced fluorescence detection module employing two diode lasers, one per separation channel. Independently controlled miniature high-voltage power supplies enable fully programmable electrokinetic sample injection and analysis. As a demonstration of the portability of this instrument, we evaluated its performance in a laboratory field test at the Defence Science and Technology Laboratory with a series of biotoxin variants. The two separation methods cleanly distinguish between members of a biotoxin test set. Analysis of naturally occurring variants of ricin and two closely related staphylococcal enterotoxins indicates the two methods can be used to readily identify ricin in its different forms and can discriminate between two enterotoxin isoforms.

Preliminary performance assessment of biotoxin detection for UWS applications using a MicroChemLab device.

“…For a given m easurement w ithout t he a nalyte p resent, t he pr obability of a false d etection i s estimated a s th e p robability th at th e e ffective a mplitude in th e time d omain o f th e a nalyte o f interest i s l arger t han o verall de tection l imit g iven b y E q. (1). T hus a s w as obt ained f or t he detection pr obability i n Eq.…”

“…This device is based on t he l iquid-phase µ ChemLab TM technology (1)(2)(3) and e mploys m icrofluidic c hip-based g el electrophoresis (CGE) for monitoring biological analytes in a small integrated sensor platform. The instrument is comprised of a sample probe for collecting a sample from the main water flow; a mic rofluidic s ample p reparation mo dule e mploying S andia d esigned f ittings, mic rofluidic pumps and el ectrically a ctuated v alves; an d t he µ ChemLab TM sample a nalysis m odule, w hich couples capillary electrophoresis separations with sensitive laser induced fluorescence detection.…”

Capillary electrophoresis of proteins 2003–2005

“…A hand-held device has been constructed for on-chip analysis of protein biotoxins in unknown mixtures [177,178]. The chip was housed in a microfluidic manifold, sealed with o-rings.…”

Bacterial characterization using protein profiling in a microchip separations platform

“…[20] and [21]). The mChemLab device developed at Sandia National Labs has been shown to be an effective tool for protein separations and combines microscale electrophoretic separations with sensitive LIF detection in a hand-portable integrated device [22][23][24].…”