Surface Plasmon-Driven Reversible Transformation of DNA-Bound Methylene Blue Detected In Situ by SERS

Abstract

We have reported the in situ surface-enhanced Raman spectroscopy (SERS) monitoring of repetitive surface plasmon-mediated chemical transformation cycles in a conjugate nanobiological system. The nanobiological conjugate comprised a gold-coated plasmonic substrate biofunctionalized with thiolated single-stranded DNA carrying a reduction-oxidation indicator methylthioninium chloride, which is also known as methylene blue (MB), in buffer solution at a neutral pH. Exposure to a 523-nm laser excitation produced pronounced SERS bands of oxidized MB. Continued exposure to the laser resulted in disappearance of the SERS bands, which can be interpreted as a reduction of MB. This occurred in the absence of electrochemical stimulation, chemical agents, or catalysts, suggesting a surface plasmon-mediated mechanism of the transformation. The oxidized form of MB was recovered by an addition of fresh buffer solution on the surface of the sample. Continued laser exposure with periodical addition of the buffer resulted in repetitive cycles of changes in the SERS pattern, which were monitored in situ. The chemical transformations of MB were preceded by a buildup of an intermediate SERS pattern, which was attributed to a transient form of MB created by selective surface plasmon-driven excitation.

A DNAzyme-mediated signal amplification biosensor for ultrasensitive detection of lead ions based on SERS tags

“…Gold nanoparticles based on this reason were chosen as the SERS signal enhancement substrate for our work. 19,20 In this article, we constructed biosensors to detect trace Pb 2+ combining SERS and rolling circle amplification (RCA) techniques. The biosensor is characterized by its high sensitivity, fast sensing speed, low cost and the possibility of continuous detection, which can be beneficial for the highly sensitive, specific, simple and rapid detection of heavy metal ions in the environment.…”