Combination of Live Cell Surface-Enhanced Raman Scattering Imaging with Chemometrics to Study Intracellular Nanoparticle Dynamics

Abstract

Surface-enhanced Raman scattering (SERS)-encoded nanoparticles are used for bioimaging, on account of their well-defined Raman spectra and biocompatibility, which allow long incubation times with high signal stability and no cytotoxicity. However, reliable analysis of SERS bioimaging requires quantification of the amount of encoded nanoparticles that have been taken up by cells and the effect of subsequent dilution due to cellular division (mitosis). Although methods such as elemental analysis and flow cytometry can be used to quantify nanoparticle uptake, these are both end-point measurements in which a cell population is screened rather than looking at individual cells. In contrast, SERS imaging can be applied at multiple timepoints to the same individual cells without damaging the biological sample. We present the application of both supervised and unsupervised multivariate analyses, to quantify the intracellular amount of SERS tags in individual MCF7 living cells, toward the characterization of cellular uptake in vitro . The obtained results from both methodologies were validated by standard elemental analysis techniques.

Hybrid Magnetic–Plasmonic Nanoparticle Probes for Multimodal Bioimaging

“…SERS Imaging of Spheroids. SERS mapping of spheroids involved placing individual spheroids inside a homemade holder 31 on top of a small drop of dental glue to fix the spheroid position.…”

SERS-Active Printable Hydrogel for 3D Cell Culture and Imaging

“…Surface-enhanced Raman spectroscopy (SERS) has emerged as a promising approach for live cell imaging since it is a highly sensitive, nondestructive, and rapid technique with the capacity for molecular fingerprinting. , SERS-based cell imaging strategies can be classified as either labeled or label-free. Labeled SERS cell imaging is similar to fluorescence imaging wherein the signal of a prefunctionalized Raman responsive molecule is tracked while targeting molecules of interest. − In label-free SERS imaging, the fingerprint signals of the cellular components are directly monitored. These signals simultaneously reflect multisubcellular components and potentially provide the capacity for cell differentiation and identification of altered phenotypes. , In 3D imaging, the label-free approach is more promising since SERS hot spots can be integrated into the cell culture matrix, and no chemical modification or nanoparticle penetration is required for imaging.…”

“…Recently, researchers have begun applying 3D label-free SERS imaging in scaffold-based cell culture to avoid the poor reproducibility caused by the random cellular uptake of nanoparticles and nanoparticle aggregation. SERS-active hydrogels have been successfully produced for 3D cell culture and label-based cell imaging and shown promise for pH measurement, metabolite sensing, and drug diffusion monitoring. ,,− However, to the best of our knowledge, true label-free SERS-based 3D cell imaging in a hydrogel cell culture system has yet to be achieved.…”

Accurate Quantification and Imaging of Cellular Uptake Using Single-Particle Surface-Enhanced Raman Scattering

“…21,22 Recently, digital methods for detecting SERS have circumvented the intensity variation challenge and enabled dynamic measurement of NPs in cells, but this often sacrifices spatial resolution to obtain accurate quantification. 23,24 In digital SERS, multiple measurements must be made across an area for quantification of particle number within the total region measured. 23 Advances in NP design have enabled bright and reproducible SERS signals, leading to greater potential for the quantitative SERS imaging of NPs.…”

“…23,24 In digital SERS, multiple measurements must be made across an area for quantification of particle number within the total region measured. 23 Advances in NP design have enabled bright and reproducible SERS signals, leading to greater potential for the quantitative SERS imaging of NPs. Previously synthesized and characterized ultrabright NPs have been shown to be useful for rapid imaging applications.…”