test forensic

Forensics   

 


Dr. Katja ANSLINGER, from Ludwig-Maximilians-University of Munich, discusses her latest findings in the field of single-cell forensics using the DEPArray NxT

 

Mixed samples are the last unresolved issue in forensic genetics. 

Current approaches to resolve mixed biological evidence profiling include the chemical reduction of one cell type (differential lysis) or the use of informatics algorithms to deconvolute mixed profiles. These methods are limited however to mixtures of sperm/epithelial cells and to a limited range of cell ratios.

DEPArray technology is particularly well suited for forensic samples thanks to very high precision digital sorting and very limited requirement for sample input; a few hundred cells can be sufficient to load a chip. Single cells can be identified and recovered with high precision thanks to the use of immunofluorescent markers and imaging.

With DEPArray, we introduce three innovative solutions for mixed forensic sample analysis:

  • Simultaneous cell identification and profiling: determine the STR profile corresponding to each type of cell in a mixed sample;
  • Pure cell analysis: sufficient to resolve cases of 2 contributors where the victim and the perpetrator contribute with a different cell type (sperm-epithelial, blood-epithelial, blood-sperm);
  • Single cell analysis: for more complex cases where multiple contributors share the same type of cells (blood-blood, sperm-sperm, saliva-saliva).

STR

Single cell profile of a blood cell isolated from a swab of a knife found on the crime scene of a murder. (Anslinger et al, Rechtsmedizin, Dec 2018  https://doi.org/10.1007/s00194-018-0291-1)

 

DEPArray Forensic Sample Prep Kit

Scatola_DEPArray_Forensic_Sample_Prep_Kit.jpgWith 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. 

The newly developed DEPArray Forensic Sample Prep Kit streamlines the sample preparation step before DEPArray sorting with a labor-saving and standardized 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.

flusso_forensic

 

Compatible with Existing STR Kits

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.

Single-Cell Precision

Digital sorting combines the power of immunofluorescent markers with image based selection to secure the highest precision and sensitivity in the isolation of the desired cells with 100% purity.

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Book Chapter 

Aversa et al, Forensic DNA Analysis: Technological Development and Innovative Applications 2021, "Chapter 17 - DEPArray System: Key Enabling Technology for Cell Separation from Forensic Mixtures"

 

Published Work Demonstrating Use of DEParray™ Technology in Forensics 

 

Watkins et al, Nature Scientific Reports 2021, "Revisiting single cell analysis in forensic science"

Anslinger et al, FSI Genetics Supplement Series 2019, "New strategies in the field of mixture deconvolution single cell STR profiling"

Meloni et al, FSI genetics, 2019, "Optimization of STR amplification down to single cell after DEPArray isolation"

Anslinger et al, Rechtsmedizin 2019, "Deconvolution of blood-blood mixtures using DEPArrayTM separated single cell STR profiling"

Anslinger K et al, International Journal of Legal Medicine 2018, "Whose blood is it? Application of DEPArray™ technology for the identification of individual/s who contributed blood to a mixed stain"

Williamson VR et al, FSI Genetics 2018, "Enhanced DNA Mixture Deconvolution of Sexual Offense Samples Using the DEPArrayTM System"

Aslinger K et al,  Rechtsmedizin 2017, “Application of DEPArray™ technology for the isolation of white blood cells from cell mixtures in chimerism analysis

Fontana F et al, FSI Genetics 2017, “Isolation and genetic analysis of pure cells from forensic biological mixtures: The precision of a digital approach

Hansson O et al, FSI Genetics 2017, “Characterization of artefacts and drop-in events using STR-validator and single-cell analysis

 

Posters 

Tanzi et al, AAFS 2021, "A performance evaluation of the VeriFiler™ Plus PCR amplification kit for Single Cell Forensics"

Fontana F et al, ISHI 2017, "Precise isolation of sperm cells from FFPE tissue sections simulating a sexual assault victim specimen"

Aversa R et al, ISFG 2017, "Low-count, pure, digitally-isolated cells as input for standard analysis in forensic genetics"