Plasmonic Au nanocube enhanced SERS biosensor based on heated electrode and strand displacement amplification for highly sensitive detection of Dam methyltransferase activity.

In this work, a novel "turn-on" mode Au nanocubes (AuNCs) enhanced surface-enhanced Raman scattering (SERS) biosensing platform coupled with heated Au electrode (HAuE) and strand displacement amplification (SDA) strategy was proposed for highly sensitive detection of DNA adenine methylation (Dam) Methyltransferase (MTase) activity. The Dam MTase and DpnI enzyme activities were significantly increased by elevating the HAuE surface temperature, resulting in the rapid production of template DNA for later SDA. During the SDA process, the released single-stranded DNA (ssDNA) could be amplified exponentially, and its concentration was positively related to the Dam MTase activity. The plasmonic AuNCs in SERS tags could provide significant SERS enhancement due to their "lightning rod" effect resulting from the sharp feature of the edges and corners of AuNCs. Because of these factors, the proposed biosensors exhibited high sensitivity in detecting the Dam MTase activity. The limit of detection was estimated to be 8.65 × 10 U mL, which was lower than that in most of the sensors for detection of Dam MTase activity in the literature. This SERS biosensor could also be used to screen inhibitors of Dam MTase and had the potential for detecting Dam MTase activity in real biological samples.