Automated Processing of Forensic Casework Samples Using Robotic Workstations Equipped with Nondisposable Tips: Contamination Prevention

TLDR

An automated forensic workflow was established on TECAN Genesis RSP 150/8 or Freedom EVO liquid‑handling workstations that use only nondisposable tips, incorporating strategically placed tip‑cleaning routines during DNA extraction and at session end, with multiple cleaning strategies tested to verify cross‑contamination control. A 2 % sodium hypochlorite wash proved most effective at preventing cross‑contamination without compromising STR profiles, enabling cost‑effective use of fixed tips in robotic magnetic‑bead DNA extraction.

Abstract

Abstract: An automated process has been developed for the analysis of forensic casework samples using TECAN Genesis RSP 150/8 or Freedom EVO liquid handling workstations equipped exclusively with nondisposable tips. Robot tip cleaning routines have been incorporated strategically within the DNA extraction process as well as at the end of each session. Alternative options were examined for cleaning the tips and different strategies were employed to verify cross‐contamination. A 2% sodium hypochlorite wash (1/5th dilution of the 10.8% commercial bleach stock) proved to be the best overall approach for preventing cross‐contamination of samples processed using our automated protocol. The bleach wash steps do not adversely impact the short tandem repeat (STR) profiles developed from DNA extracted robotically and allow for major cost savings through the implementation of fixed tips. We have demonstrated that robotic workstations equipped with fixed pipette tips can be used with confidence with properly designed tip washing routines to process casework samples using an adapted magnetic bead extraction protocol.