Crime scene investigation requires collection and analysis of biological evidence for DNA genotyping. Blood, sperm, and epithelial evidence left behind by perpetrators can help investigators acquire a genetic profile of the person who committed the crime.
Submitted by: Menarini Silicon Biosystems
A problem occurs when a single evidence sample consists of biological fluids contributed by two or more persons (e.g. the victim and the perpetrator). Forensic scientists refer to these samples as “mixed biological evidence.”
Current approaches to mixed biological evidence analysis have limitations, due to the fact they produce mixed genetic profiles, which can only be interpreted by statistical assumptions that introduce uncertainty and often compromise the forensic value of laboratory findings.
The DEPArray™ system resolves this uncertainty by enabling forensic laboratory scientists to separate blood cells, from epithelial cells, from sperm cells, with 100% precision. Such separation, prior to genetic analysis, allows distinct profiling of multiple individual contributors by routine DNA identification methods.
The DEPArray™ system is a benchtop instrument that consists principally of a fluorescence microscope, a digital camera, software, and a disposable microfluidic cartridge containing large two-dimensional arrays of paired electrodes on opposing sides of a thin liquid volume. The system interrogates mixed cell suspensions for cell characteristics such as size, morphology, surface markers, and DNA content. Dielectrophoretic forces induced under software control between electrode pairs enable single cell entrapment and mobilization, for selection, isolation, and recovery of specific, individual cells. The system is differentiated from conventional cell sorting and selection technologies by the ability to pick out specific, individual cells, from a complex heterogeneous sample, for isolation, collection, and analysis.
With the ability to analyze even minute mixed biological evidence, the DEPArray™ system can separate epithelial cells, white blood cells, and sperm cells, and recover 100% pure pools of cells for standard forensic analysis profiles produced from these separated samples represent a fundamental step in assigning the precise and distinct genetic fingerprints from each contributor.
When a sample is composed of a single cell type (such as epithelial cells, or sperm cells), but the contribution of multiple individuals is suspected, the ability of the DEPArray™ system to single out and collect single cells for analysis may enable confident DNA-based identification, based on unambiguous STR profiles, of more than one individual.
The newly developed DEPArray Forensic Sample Prep Kit streamline the sample preparation step before DEPArray sorting with a labor-saving and standardize procedure. The kit includes all the reagents to process the sample from the evidence support material to the DEPArray cartridge and has been specifically designed for the staining of epithelial, sperm and white blood cells before DEPArray sorting.
The workflow below allows the recovery of multiple groups of 100% pure samples for clear-cut genetic profiling.
Cells selected, isolated, and collected by the DEPArray system are compatible with DNA-based human identification kits, instrumentation, and software from a variety of suppliers.
The DEPArray™ system is non-destructive, and is even used to prepare pure populations of living cells for non-forensic genetic research applications. Cells selected, isolated, and collected by the DEPArray system are compatible with DNA-based human identification kits, instrumentation, and software from a variety of suppliers.
Menarini Silicon Biosystems’ Vendor Showcase is being held in conjunction with the 2016 International Symposium of Human Identification in Minneapolis, MN. The workshop on Tuesday, September 27th from 5:30pm – 7:30pm will feature an informative lecture on how DEPArray technology can resolve heterogeneity in forensic biological mixtures.
Dr. Francesca Fontana will share product updates, a technology overview and forensic applications.
Please come and join the Menarini Silicon Biosystems team for an evening of innovative forensic science discussions, while enjoying light refreshments and drinks.