Single cell analysis using surface enhanced Raman scattering (SERS) tags

Abstract

Fluorescence is a mainstay of bioanalytical methods, offering sensitive and quantitative reporting, often in multiplexed or multiparameter assays. Perhaps the best example of the latter is flow cytometry, where instruments equipped with multiple lasers and detectors allow measurement of 15 or more different fluorophores simultaneously, but increases beyond this number are limited by the relatively broad emission spectra. Surface enhanced Raman scattering (SERS) from metal nanoparticles can produce signal intensities that rival fluorescence, but with narrower spectral features that allow a greater degree of multiplexing. We are developing nanoparticle SERS tags as well as Raman flow cytometers for multiparameter single cell analysis of suspension or adherent cells. SERS tags are based on plasmonically active nanoparticles (gold nanorods) whose plasmon resonance can be tuned to give optimal SERS signals at a desired excitation wavelength. Raman resonant compounds are adsorbed on the nanoparticles to confer a unique spectral fingerprint on each SERS tag, which are then encapsulated in a polymer coating for conjugation to antibodies or other targeting molecules. Raman flow cytometry employs a high resolution spectral flow cytometer capable of measuring the complete SERS spectra, as well as conventional flow cytometry measurements, from thousands of individual cells per minute. Automated spectral unmixing algorithms extract the contributions of each SERS tag from each cell to generate high content, multiparameter single cell population data. SERS-based cytometry is a powerful complement to conventional fluorescence-based cytometry. The narrow spectral features of the SERS signal enables more distinct probes to be measured in a smaller region of the optical spectrum with a single laser and detector, allowing for higher levels of multiplexing and multiparameter analysis.

Recent advances in biosensor development for the detection of cancer biomarkers

“…Surface-enhanced Raman scattering (SERS) is gaining extensive interest for the development of cancer biosensors because of its comparable sensitivity to fluorescence based methods (Nolan et al 2012). Ouyang et al (2016) have used AuNPs modified with methylationsensitive antibody in a SERS platform to detect methylated DNA and its oxidation derivatives in real cell samples.…”

Cancer characterization and diagnosis with SERS-encoded particles

“…Although SERS microspectroscopy has been extensively employed in the study of tumor tissues (this will be discussed extensively in the next section), the phenotypic characterization of single cells is still in its infancy (Altunbek et al 2016;Chourpa et al 2008;Hu et al 2016;Kneipp 2017;Nolan et al 2012;Taylor et al 2016). The rationale of using SERS for single cell studies over other imaging techniques, such as those based on fluorescence read-outs, rests on its high multiplexing capabilities, sensitivity and robustness to investigate the distinct properties of cancer cells, in particular by exploiting antibody-conjugated SEPs targeting cell membrane receptors for immunophenotyping studies.…”

Analysis and differentiation of seminal plasma via polarized SERS spectroscopy

“…In recent years, the SERS applications were successfully used for detecting biological materials, with good stability and reproducibility (eg, SERS Raman spectra of DNA/ RNA, 7 cells, 8 and glucose 9 ). In our previous studies, we have successfully explored the application of SERS spectroscopy for cancer diagnosis based on blood plasma.…”