Target switching catalytic hairpin assembly and gold nanoparticle colorimetric for EGFR mutant detection

The detection of circulating tumor DNAs (ctDNAs) with high sensitivity plays an important role in liquid biopsy diagnosis. For the detection of ctDNAs, we investigated the applicability of a two-ways CHA technique and found there were several problems such as sensitivity and selectivity. For this reason, we revised our technique to three-ways target switching catalytic hairpin assembly (TSCHA). Our target DNA is epidermal growth factor receptor (EGFR) mutation DNA. EGFR mutation DNA is very long DNA (84 mer) and it is hard to detect such a long DNA. However, with a TSCHA method, we can produce a short catalyst DNA (c-DNA) using long target DNA. After the catalytic reaction between DNAs, AuNPs aggregate and the detection solution become blue from red. We quantify the aggregation by observing UV-vis spectrum and can obtain LOD as low as 7.7 fM. Also the selectivity of the detection method is very high. Because of the high sensitivity, high selectivity, and simplicity, the TSCHA technique has great potential as a platform to detect mutant DNA in blood of cancer patients.