Ultrasensitive colorimetric carcinoembryonic antigen biosensor based on hyperbranched rolling circle amplification.

In this study, a hyperbranched rolling circle amplification (HRCA)-based colorimetric biosensor for carcinoembryonic antigen (CEA) is developed with high sensitivity and specificity. A CEA aptamer can bind with its target (CEA) to form a complex due to their high affinity, and the introduced CDNA cannot hybridize with the aptamer. Thus, free CDNA can propagate the HRCA reaction to form a large number of single-stranded DNA (ss-DNA). ss-DNA can be easily adsorbed onto AuNPs and prevent salt-induced AuNPs aggregation, which causes the change in the color of the system. It is found that the absorbance intensity ratio (A520/A660) has a linear relationship with the concentration of the target in the range of 5 pM-0.5 nM, and the detection limit is as low as 2 pM (S/N = 3).