Multiplex SERS Detection of Metabolic Alterations in Tumor Extracellular Media

Abstract

The composition and intercellular interactions of tumor cells in the tissues dictate the biochemical and metabolic properties of the tumor microenvironment. The metabolic rewiring has a profound impact on the properties of the microenvironment, to an extent that monitoring such perturbations could harbor diagnostic and therapeutic relevance. A growing interest in these phenomena has inspired the development of novel technologies with sufficient sensitivity and resolution to monitor metabolic alterations in the tumor microenvironment. In this context, surface-enhanced Raman scattering (SERS) can be used for the label-free detection and imaging of diverse molecules of interest among extracellular components. Herein, the application of nanostructured plasmonic substrates comprising Au nanoparticles, self-assembled as ordered superlattices, to the precise SERS detection of selected tumor metabolites, is presented. The potential of this technology is first demonstrated through the analysis of kynurenine, a secreted immunomodulatory derivative of the tumor metabolism and the related molecules tryptophan and purine derivatives. SERS facilitates the unambiguous identification of trace metabolites and allows the multiplex detection of their characteristic fingerprints under different conditions. Finally, the effective plasmonic SERS substrate is combined with a hydrogel-based three-dimensional cancer model, which recreates the tumor microenvironment, for the real-time imaging of metabolite alterations and cytotoxic effects on tumor cells.

3D‐Printed Biocompatible Scaffolds with Built‐In Nanoplasmonic Sensors

“…The lowest concentration that could be reliably distinguished using these scaffolds was 100 × 10 −9 m , which lies within the range of metabolite concentrations typically observed in biological environments, such as the tumor microenvironment. [ 36 ]…”

“…The lowest concentration that could be reliably distinguished using these scaffolds was 100 nM, which lies within the range of metabolite concentrations typically observed in biological environments, such as the tumor microenvironment. [36] Although elasticity measurements (see above) indicated that the surface coating on AuNPs has a negligible effect on the rheological properties of HAMCA inks, the accessibility of the analyte molecules to the plasmonic gold NP surface is likely to hinder the SERS efficiency when NPs are stabilized with PEG. We therefore recorded 2D SERS maps for scaffolds containing AuNRs, AuNSs, AuNRs@PEG and AuNS@PEG.…”

“…[34,35] We recently reported the use of SERS to monitor relevant tumor metabolites in microfluidic cell cultures, using nanostructured plasmonic gold substrates, providing overall information about tumor evolution, but lacking spatial resolution. [36] Aiming at spatial resolution in three dimensions, we propose the use of DIW-3D printing to fabricate SERS-active scaffolds from a composite ink containing plasmonic gold nanoparticles (Scheme 1). We analyzed the influence of nanoparticle shape and surface functionalization on the SERS signal intensity from the scaffolds, by investigating the limits of detection of a model Raman molecule, 4mercaptobenzoic acid (MBA), in both the lateral (XY) and axial (Z) planes.…”

Characterizing nanoplastics‐induced stress and its SERS fingerprint in an intestinal membrane model

“…[51][52][53] NP-induced differences in the cell metabolism cause changes in the composition of cells as well as the extracellular medium due to variations in the nature and quantity of the molecules uptaken by and released from the cells. [54] Although metabolomics is traditionally performed with mass spectroscopy, Raman spectroscopy, in particular surface enhanced Raman spectroscopy (SERS), has shown promise for the metabolic profiling of the cellular activity of bacterial cells and human cancer cells, [55][56][57][58][59][60] as well as for the detection of biomarkers in serum. [55,61,62] SERS is a vibrational spectroscopy that provides unique opportunities for signal amplification in aqueous media as water has low Raman cross-sections while the signal from Raman-active molecular vibrational modes in analytes can be enhanced by multiple orders of magnitude due to an electromagnetic enhancement effect in the vicinity of nanostructured noble metal surfaces.…”

“…[54] Although metabolomics is traditionally performed with mass spectroscopy, Raman spectroscopy, in particular surface enhanced Raman spectroscopy (SERS), has shown promise for the metabolic profiling of the cellular activity of bacterial cells and human cancer cells, [55][56][57][58][59][60] as well as for the detection of biomarkers in serum. [55,61,62] SERS is a vibrational spectroscopy that provides unique opportunities for signal amplification in aqueous media as water has low Raman cross-sections while the signal from Raman-active molecular vibrational modes in analytes can be enhanced by multiple orders of magnitude due to an electromagnetic enhancement effect in the vicinity of nanostructured noble metal surfaces. [63][64][65][66][67] This amplification of molecule-specific vibrational information facilitates a sensitive detection and identification of metabolites rapidly without the need for elaborate sample preparation or enrichment.…”