DNA Loss from Bead Removal During Supernatant Transfer

Symptom

Variable or reduced cfDNA yields across samples. Beads may be visible in wash supernatants or final eluate, or yield decreases progressively through the protocol.

1. 1 Magnetic separation time less than the required 2 minutes minimum at separation steps
2. 2 Weak magnet insufficient to fully pellet beads, leaving beads suspended in supernatant
3. 3 Pipette tip disturbing bead pellet during supernatant removal
4. 4 Rushing through transfers without verifying clear supernatant before pipetting

1. 1 Leave tubes on magnet for minimum 2 minutes at all magnetic separation steps
2. 2 Use a strong magnet to ensure effective bead separation and clear supernatant
3. 3 Visually confirm supernatant is completely clear and free of beads before removing
4. 4 Carefully pipette supernatant without touching or disturbing the bead pellet
5. 5 When transferring final elution, leave a small volume (1-2 µL) behind to avoid bead carryover

Related Video (2)

Thermo Fisher Scientific ★ 85

How to Isolate Cell-Free DNA from Plasma | cfDNA Purification

"Directly demonstrates the cfDNA isolation protocol and magnetic bead handling steps relevant to the failure."

JoVE (Open Access) ★ 60

MicroRNA Based Liquid Biopsy: The Experience of the Plasma miRNA Signature Classifier (MSC) for Lung Cancer Screening

"Shows cfDNA extraction in a liquid biopsy context, helpful for understanding experimental setting but less focused on bead separation technique."