Assessment of an Automated Differential Separation Utilizing a Novel Nanofiber Filter for Sexual Assault Cases

Automated and semi-automated sample processing has become more widespread with the implementation of various robotic platforms. A new robotic application for differential separation of sexual assault samples using a novel nanofiber filter was evaluated for a high-throughput laboratory system.

The Utah Bureau of Forensic Services (UBFS) established a high-throughput sample processing system to eliminate the years-long sexual assault kit backlog. Like many test-all states, UBFS is looking to continue to improve current workflows to keep pace with the number of cases submitted. Although most automated DNA laboratory processes used at UBFS accommodate ninety-six samples at a time, one area where capacity and efficiency could be improved is the differential separation process.

Automation of the differential separation process is highly desired amongst forensic laboratories. Recently, a novel device utilizing nanofiber technology has been introduced to the forensic community which further increases the capabilities and large-scale automation possibilities when used in tandem with a robotic platform. UBFS has developed a new, automated differential separation method for sexual assault samples utilizing this novel device. The method allows for the differential separation of ninety-six samples within twelve hours with minimal analyst involvement. This run time also includes two epithelial digestions (90 minutes and 30 minutes, respectively) and one sperm digestion of 45 minutes. The method is a tube-to-tube process with the final lysate being transferred into 1.5mL tubes for both the non-sperm and sperm fractions.

Samples were run in triplicate to validate the newly automated differential separation method and results were compared to the currently implemented semi-automated method used at UBFS. All samples were further analyzed using fully automated downstream processing for extraction and quantification. Select samples proceeded to automated normalization and amplification. Profiles were developed using an STR typing kit on a capillary electrophoresis instrument.

Similar results were obtained between the semi- and fully automated methods based on male recovery percentage and STR profiles. However, when examining samples containing low levels of spermatozoa, the new, fully automated method outperformed the semi-automated method in total recovered male DNA.

Overall, this new method increases throughput and time efficiencies while maintaining individual sample integrity. The method could be easily implemented in any laboratory setting and would help considerably with large-scale processing of sexual assault samples while freeing up analyst time to perform other, more complex, tasks.