Polyacrylamide/Phytic Acid/Polydopamine Hydrogel as an Efficient Substrate for Electrochemical Enrichment of Circulating Cell-Free DNA from Blood Plasma

A facile method has been developed for the rapid and efficient enrichment of DNAs from different media including synthetic single-strand DNAs (ssDNAs) from buffer solutions and cell-free DNAs (cfDNAs) from blood plasma through electric field-driven adsorption and desorption of DNAs by a polyacrylamide/phytic acid/polydopamine (PAAM/PA/PDA) hydrogel. The as-prepared PAAM/PA/PDA hydrogel possesses regular porosity with a large surface area, strong electric field responsiveness/good conductivity, and a rich aromatic structure, which can be used as an ideal adsorbent for DNA enrichment under a positive electric field. The enriched DNAs can be released efficiently when the positive electric field is converted to a negative electric field. The PAAM/PA/PDA hydrogel-based electrochemical method enables the completion of the process of DNA adsorption and release within 5 min and exhibits reasonable enrichment efficiencies and recovery rates of various DNAs. For instance, the high enrichment sensitivity (0.1 pmol L -1 ) together with the excellent recovery (>75%) of an ssDNA with 78 nucleotides is obtained. Combined with the PCR amplification technique, the practicability of the as-proposed method is demonstrated by the screening of circulating tumor DNAs (ctDNAs) with a BRAF V600E mutation in cfDNAs from the blood plasma samples of patients with papillary thyroid cancer or thyroid nodule and random patients from a clinical laboratory.