A dual-probe surface-co-immobilization-based electrochemical sensor for highly sensitive and tunable specific detection of a designated DNA

摘要

A "signal on" electrochemical sensing method was established for the detection of a designated 24-base DNA. This sensor system shows a simple structure with only composing of three probes. One capturing probe (CP) and one assistant probe (AP) are co-immobilized onto the Au electrode surface in a short CP/AP duplex state, and one methylene blue (MB) modified signaling probe (SP) is free in the detection solution. Before adding the target, a low background signal helpful for improving the sensitivity is obtained with low efficient electron transfer because of the MB labels far from the electrode surface; after adding the target, the longer and more stable CP/target duplex formed between CP and the target undoes the former CP/AP duplex to release the AP, which induces the formation of another AP/SP duplex. This structure can drive the MB labels close to the electrode surface with much higher efficient electron transfer, thereby producing a large detection signal. The proposed sensor features a high sensitivity with the detection limit (DL) of ～10 fM for the target. When used for discriminating the mismatched target, the sensor also exhibits a good ability and its high adjustability.