Low-cost, enzyme-free extraction of cell-free DNA (cfDNA) from human plasma for liquid biopsy using SDS lysis and NaCl salting-out v1
Year: 2026
Type: preprint
Abstract: Liquid biopsy detects tumour-derived biomarkers, mainly circulating cell-free DNA (cfDNA), from a simple blood draw instead of an invasive tissue biopsy. Commercial cfDNA extraction kits are expensive, import-dependent and rely on sensitive enzymes, which limits their use in resource-limited laboratories. This protocol describes a locally prepared, enzyme-free ("frugal") kit that isolates cfDNA from 3 mL of EDTA whole blood using only basic reagents: 10% SDS for lysis, saturated NaCl (~6 M) for protein salting-out, and cold absolute ethanol for precipitation. A two-step centrifugation (soft spin, then hard spin) yields the plasma with minimal genomic DNA (gDNA) contamination. The concentrated cfDNA (~166 bp fragments) is verified on a high-percentage (2–2.5%) agarose gel, where a successful extraction appears as a faint low-molecular-weight band or smear below the smallest ladder band, with no high-molecular-weight gDNA near the wells. Total time: ~4 h hands-on + incubation (≥ 2 h, preferably overnight, at −20 °C).
Language: English
Subfield: Cancer Research
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7221890604