Gold nanocube-enhanced SERS biosensor based on heated electrode coupled with exonuclease III-assisted cycle amplification for sensitive detection of flap endonuclease 1 activity

The flap endonuclease 1 (FEN1) plays a key role in DNA replication and repair, its aberrant expression is associated with tumor development, so it has been recognized as a promising biomarker for a variety of cancers. Here, a novel "turn on" mode gold nanocube-enhanced surface-enhanced Raman scattering (SERS) biosensor was constructed by combining a heated Au electrode (HAuE), exonuclease III (Exo III)-assisted cycle amplification, and gold nanocube (AuNC)-based SERS enhancement to achieve highly sensitive detection of FEN1 activity. The SERS tag was prepared using the Raman reporter modified on the AuNC surface, and the high electromagnetic field provided by the sharp geometric feature of AuNC greatly enhanced the SERS signal. At the same time, HAuE was used to increase the electrode surface temperature and enhance the FEN1 activity, leading to more trigger DNA being cleaved, which was used to initiate the Exo III-assisted cycle amplification. Taking all these advantages, the proposed method possessed high sensitivity and good selectivity, with a low limit of detection (LOD) of 3.19 × 10^-7 U μL^-1. In addition, this method was successfully applied to detect FEN1 activity in real cellular extracts.