Nucleic Acid Detection
Applied Biosystems, part of Life Technologies, presented an automated procedure and workflow for high-throughput sample preparation using its PrepSEQ Nucleic Acid Extraction Kit at the symposium. The procedure presented by Nan Liu, a senior scientist, consisted of sample lysis, nucleic acids binding to the magnetic beads, washing, and elution on a MagMax-Express automated magnetic particle processor.
Getting adequate quality and concentrations of nucleic acid is crucial, and Life Technologies’ magnetic particle chemistry is a key differentiator for nucleic acid recovery, noted Maxim Brevnov, senior staff scientist. “Our optimized magnetic particle chemistry provides effective capture on large surface area making a high nucleic acid recovery rate possible for a broad range of sample sizes, yielding from femtograms to micrograms of highly purified nucleic acids. Even with complex samples, we can deliver consistent and accurate results.”
Jenkui Liu, a senior staff scientist, noted that this technology can be used for both automated and manual systems. “Two major attractions to users are the performance of the magnetic particles in automation procedures and the ability of the chemistry to deal with diverse sample types. We have demonstrated that the PrepSEQ chemistry and purification procedures can be easily automated in different instruments up to 96 samples each time. Automated and manual procedures produced similar results in getting accurate reads and high DNA recovery from diverse sample types.”
Nan Liu noted that isolation and purification of nucleic acids at low levels from chemically complicated and PCR-incompatible samples can be done with the system. “Detection of low-level residual DNA from biological drugs has been challenging. The level of DNA in the samples can be in the picogram range, and we can achieve DNA recovery as high as >95% with our system.
“The resultant purified DNA shows high efficiency in TaqMan PCR assays, so we are able to detect residual DNA levels that are much lower than the limit in FDA regulations. Our system can also provide more accurate quantification of DNA in the drugs in diverse matrices.”
Preconcentration of Proteins
Addressing another angle of the preconcentration problem was Anson Hatch, Ph.D., research scientist in the biosystems research department at Sandia National Laboratories. “We are developing microfluidic medical diagnostic platforms but have realized that rapid point-of-care diagnostics demand attention in the sample-prep realm,” he said.
Dr. Hatch’s work focuses on lab-on-a-chip approaches for rapid detection of biomolecules in trace quantities in complex biofluids and matrixes such as blood, saliva, or extracted cells. “Our group is developing a number of on-chip capabilities including sample preparation.”
At the symposium, Dr. Hatch described a suite of microfluidic sample-prep modules in development that are specifically designed for isolating protein fractions from complex samples. “The modules include size-based filtration of cells and particulate matter, immunodepletion of high-abundance interfering proteins, isoelectric fractionation of proteins, and preconcentration membranes that mix and enrich proteins greater than 10,000-fold. All elements can be integrated in various arrangements for rapid, streamlined processing and analysis.”