Ultrasensitive SERS Profiling of Intracellular Hydrogen Peroxide Release Based on Enzymatic Amplification and Silent-Region Raman Reporter
Jindan Wu, Kaixin Chen, Junming Pan, Dehua Li, Ying Ma, Nan Li
Abstract
Surface-enhanced Raman scattering spectroscopy (SERS) has been widely applied to screen biomarkers and biological species due to its high sensitivity; however, severe background noise signals significantly limit its practical application. In this study, we develop an ultrasensitive SERS sensor to determine cellular oxidative stress based on the H 2 O 2 -induced enzymatic amplification and a silent-range Raman fingerprint. In the presence of horseradish peroxidase, H 2 O 2 could trigger the coupling reaction of 4-hydroxythiophenol (4-MTP) with phenol-d5 to form a new compound, which can bind to the SERS substrate via the Au–S bond and generate the stable SERS signal with nearly zero background signals owing to the Raman-silent fingerprint of phenol-d5 at 2125 cm –1 . The high-performance enzymatic reaction and the silent-range Raman fingerprint enable the ultrasensitive determination of H 2 O 2 with a broad linear range of 5 × 10 –9 to 1 × 10 –3 M and a limit of detection as low as 1.6 nM. Taking advantage of its excellent sensitivity and anti-interference capability, the as-developed SERS sensor is employed to profile the triggered dynamic change of the intracellular H 2 O 2 release, and further to testify the cancerous cells exhibiting a significantly higher level of intracellular oxidative stress than the healthy cells, and the different cell populations possessing the susceptible difference to additional oxidative stimulation. This study paves the way for improving SERS sensing capability through the silent-range fingerprint and signal amplification via an enzymatic reaction and reveals SERS as an effective tool for monitoring the endogenous oxidative behavior of living cells.