Capillary sample introduction of polymerase chain reaction (PCR) products separated in ultrathin slab gels

Improving resolution for channel-format chip-based electrophoresis with electrochemical array detection

Resolution in channel electrophoresis has been improved by means of the addition of a surfactant to the running buffer and minimization of the channel internal height and sampling capillary internal diameter. Micellar electrokinetic channel chromatography with electrochemical detection has been applied to the separation of several cationic catecholamines and has been used to continuously monitor a dynamic system of dopamine, norepinephrine, and epinephrine. Resolution was also enhanced by coupling small internal-diameter (5 microm) sampling capillaries with sub-micrometer internal-height separation channels. The improvements in resolution offered by these methods will extend the applicability of channel electrophoresis with electrochemical detection to more complex samples while permitting sample volumes in the nL range to be probed.

DNA separations in microfabricated devices with automated capillary sample introduction

A novel method is presented for automated injection of DNA samples into microfabricated separation devices via capillary electrophoresis. A single capillary is used to electrokinetically inject discrete plugs of DNA into an array of separation lanes on a glass chip. A computer-controlled micromanipulator is used to automate this injection process and to repeat injections into five parallel lanes several times over the course of the experiment. After separation, labeled DNA samples are detected by laser-induced fluorescence. Five serial separations of 6-carboxyfluorescein (FAM)-labeled oligonucleotides in five parallel lanes are shown, resulting in the analysis of 25 samples in 25 min. It is estimated that approximately 550 separations of these same oligonucleotides could be performed in one hour by increasing the number of lanes to 37 and optimizing the rate of the manipulator movement. Capillary sample introduction into chips allows parallel separations to be continuously performed in serial, yielding high throughput and minimal need for operator intervention.

Ultrathin-layer gel electrophoresis of biopolymers

Emerging need for large-scale, high-resolution analysis of biopolymers, such as DNA sequencing polymerase chain reaction, (PCR) product sizing, single nucleotide polymorphism (SNP) hunting and analysis of protein molecules necessitated the development of automated and high-throughput gel electrophoresis based methods enabling rapid, high-performance separations in a wide molecular weight range. Scaling down electric field mediated separation processes supports higher throughput due to the applicability of higher voltages, thus speeding up analysis time. Indeed, efforts in miniaturization resulted in faster, easier, less costly and more convenient analyses, fulfilling the needs of the emerging biotechnology industry for microscale and massively parallel assays. The two primary approaches in miniaturizing electrophoresis dimensions are the capillary and microslab formats. This latter one evolved towards ultrathin-layer gel electrophoresis which is, except from the thickness of the separation platform, slightly in the upper side of the scale, resulting in considerably easier handling. Ultrathin-layer gel electrophoresis combines the advantages of conventional slab-gel electrophoresis (multilane format) and capillary gel electrophoresis (rapid, high-efficiency separations). It is readily automated, automatic versions of it have been extensively used for large-scale DNA sequencing in the Human Genome Project and more recently became popular in high throughput DNA fragment analysis. Ultrathin-layer techniques are the first step towards the wider use of electrophoresis microchips in perfecting a user-friendly interface between the user and the microdevice.

Human dopamine D4 receptor allele genotyping by ultrathin agarose gel electrophoresis with To-Pro-3 complexation

Growing evidence shows the correlation between the allelic type of the dopamine D4 receptor and the human novelty-seeking personality trait. A sensitive, ultrathin agarose gel electrophoresis-based, high-throughput screening method was developed for genotyping the dopamine D4 receptor (D4DR) exon III 48 base pair repeat polymorphism. The efficiency of the method was increased by reamplification nested polymerase chain reaction (PCR) - of the 48 base pair repeat containing the PCR product with internal primers. The nested PCR fragments were analyzed by ultrathin layer agarose gel electrophoresis with an automated real-time laser-induced fluorescent detection system. Noncovalent affinity complexation was accomplished during the separation process by the addition of a very low concentration of intercalation dye, To-Pro-3 (2 nM) to the gel buffer system. This resulted in instant fluorescent labeling of the migrating PCR fragments. This method can readily facilitate genetic association studies between dopamine receptor genotypes and some human behavioral and neuropsychiatric disorders.

Molecular genetic diagnosis of de novo and recurrent bladder cancer

Bladder cancer, the second most common urological tumor, is usually diagnosed by endoscopy and biopsy of the lower urinary tract. However, this procedure is expensive, can cause discomfort to the patient and is a source of infection. Commercially available diagnostic systems measure protein byproducts of bladder carcinoma in voided urine; their sensitivity is only between 60-80%. Polymerase chain reaction (PCR)-based microsatellite analysis of the urine sediment (MAUS) is a noninvasive, inexpensive and easily performed analytical method which was introduced in the de novo diagnosis and follow-up of bladder cancer. By utilizing the PCR with 20 polymorphic microsatellite markers on different chromosomes and separating PCR products by electrophoresis on 7% denaturing polyacrylamide-formamide-urea slab gels, a 91% diagnostic sensitivity could be achieved. In order to minimize costs and analysis time, the separation and detection of PCR products was carried out by capillary array electrophoresis and two-color fluorescent primer labeling/laser beam detection in another study. The accuracy of both methods was the same. In either detection system, MAUS is an accurate and promising tool in the noninvasive diagnosis of bladder cancer.

Monitoring cellular release with dynamic channel electrophoresis

A channel electrophoresis system consisting of a 50 microns by 75 mm by 25 mm separation channel has been adapted to follow stimulated release from individual and small groups of isolated neurons. The cells of interest are placed in a nanoperfusion chamber located near the exit of a sampling capillary. The capillary is scanned across the mouth of the channel so that compounds released from the cells are dynamically introduced into the separation channel. The position of the sampling capillary along the channel entrance yields temporal information, and electrophoresis in the channel length dimension provides the chemical data. NDA/CN- is placed in the inlet vial between the sampling capillary and channel so that primary amine-containing compounds released from the cell are derivatized prior to separation as they enter the channel. The performance of this method is evaluated, and the optimum NDA/CN- concentration and separation conditions for this on-line derivatization are presented, with detection limits for most underivatized amino acids of approximately 500 nM at a particular time slice. The time-resolved electropherograms from single and a small group of cerebral ganglion neurons from Aplysia californica stimulated with KCl show multiple components released with different time courses.