Electrostimulus-associated PD-L1 expression on cell membrane revealed by immune SERS nanoprobes

Designing SERS nanotags for profiling overexpressed surface markers on single cancer cells: A review

This review focuses on the chemical design and the use of Surface-Enhanced Raman Scattering (SERS)-active nanotags for measuring surface markers that can be overexpressed at the surface of single cancer cells. Indeed, providing analytical tools with true single-cell measurements capabilities is capital, especially since cancer research is increasingly leaning toward single-cell analysis, either to guide treatment decisions or to understand complex tumor behaviour including the single-cell heterogeneity and the appearance of treatment resistance. Over the past two decades, SERS nanotags have triggered significant interest in the scientific community owing their advantages over fluorescent tags, mainly because SERS nanotags resist photobleaching and exhibit sharper signal bands, which reduces possible spectral overlap and enables the discrimination between the SERS signals and the autofluorescence background from the sample itself. The extensive efforts invested in harnessing SERS nanotags for biomedical purposes, particularly in cancer research, highlight their potential as the next generation of optical labels for single-cell studies. The review unfolds in two main parts. The first part focuses on the structure of SERS nanotags, detailing their chemical composition and the role of each building block of the tags. The second part explores applications in measuring overexpressed surface markers on single-cells. The latter encompasses studies using single nanotags, multiplexed measurements, quantitative information extraction, monitoring treatment responses, and integrating phenotype measurements with SERS nanotags on single cells isolated from complex biological matrices. This comprehensive review anticipates SERS nanotags to persist as a pivotal technology in advancing single-cell analytical methods, particularly in the context of cancer research and personalized medicine.

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.

Electrostimulus-triggered reactive oxygen species level in organelles revealed by organelle-targeting SERS nanoprobes

Electrostimulation (ES) is an important therapeutic method for diseases caused by abnormal intracellular electrical activity. Also, it can induce apoptosis of cells, which is a potential tumor treatment method. At present, there are no relevant studies on changes in intracellular reactive oxygen species (ROS) levels produced in the process of ES, or on the effects of simultaneous implementation of conventional antioxidant inhibitor drugs and ES therapy. To reveal these, two organelle-targeting core-shell plasmonic probes were designed for measuring ROS produced during ES. The probes were delivered into target organelles (nucleus and mitochondrion) before the cells were electrically stimulated for different periods of time. Surface-enhanced Raman scattering (SERS) signals were detected in situ, and the sensing mechanism for the quantitative analysis of ROS is based on the signal reduction of SERS caused by the ROS-etching effect on the silver shell. The detection results revealed that ES could trigger ROS generation in cells, and the ROS levels localized around organelles were assessed by SERS. This study has great potential for exploring abnormal organelle microenvironments via organelle-targeting probes combined with SERS technology.