Label-Free SERS Detection of Protein Damage in Organelles under Electrostimulation with 2D AuNPs-based Nanomembranes as Substrates.

Proteins as the material basis of life are the main undertakers of life activities. However, it is difficult to identify the related proteins in organelles during stimuli-induced stress responses in cells and remains a great challenge in early diagnosis and treatment of disease. Here, proteins in the cell nucleus and mitochondria of cells under the electrical stimulation (ES) process were collected and sensitively detected based on label-free surface-enhanced Raman spectroscopy (SERS) by using AuNP-based nanomembranes as high-performance SERS substrates. Due to the existence of rich "hot spots" on the 2D plasmonic sensing platform, high-quality SERS spectra of proteins were obtained with superior sensitivity and repeatability. From the SERS analyses in vitro, it was found that the conformation of some proteins in the two kinds of organelles from cancerous HCT-116 cells (compared with normal NCM-460 cells) changed significantly and the expression levels of tyrosine, phenylalanine, and tryptophan were significantly promoted during the stimulation process. Although currently the exact proteins are still unknown, the damage of proteins in the organelles of cells at the amino acid level under ES can be revealed by the method. The developed plasmonic SERS sensing platform would be promising for bioassay and cell studies.