Highly sensitive electrochemical detection of circulating tumor DNA in human blood based on urchin-like gold nanocrystal-multiple graphene aerogel and target DNA-induced recycling double amplification strategy.

Detection of circulating tumor DNA (ctDNA) is important approach to risk stratification and treatment response monitoring of cancer patients, but current method lacks of enough sensitivity and repeatability. The paper repors shape-controlled synthesis of gold nanocrystals via reduction of HAuCl4 with ascorbic acid. The synergy of CTAC, KBr, KI and L-glutathione creates urchin-like gold nanocrystals (U-Au) with more exposed high-index facets. Preparation of electrochemical sensing platform for ctDNA involves modification of U-Au-multiple graphene aerogel for target DNA-induced recycle amplification. DNA probe 1 (P1) with methylene blue (MB) hybridizes with DNA probe 2 with ferrocene (Fc) to form duplex DNA, which was attached to U-Au through Au-S bond. The ctDNA hybridizes with hairpin DNA 1 to open hairpin structure, triggering target DNA-induced recycle. Utilization of target DNA-induced recycling allows one target DNA to approach many MB probes to electrode surface and to leave many Fc probes from electrode surface, promoting significant signal amplification. The detection signal is enhanced by catalyzed redox of Fc and MB. Electrochemical response increases with ctDNA concentration from 0.1 to 1 × 106 fM with detection limit of 0.033 fM. The biosensor provides ultrahigh sensitivity, specificity and stability and was successfully applied in detection of ctDNA in human blood.