Chemical Mapping of Leishmania Infection in Live Cells by SERS Microscopy

Abstract

We report the direct probing of the molecular composition of Leishmania-infected macrophage cells in vitro by surface-enhanced Raman scattering (SERS). The microscopic mapping data indicate local abundance and distribution of molecular species that are very characteristic of the infection and that are observed here simultaneously. As revealed by electron microscopy, the gold nanoprobes used for SERS microspectrosopy have access to the parasitophorous vacuoles (PV) through the endosomal system. SERS nanoprobes located in the direct proximity to the parasite, in the greater volume of the PV, and in endolysosomal compartments in other cellular regions, respectively, report a characteristic chemical composition for each respective location. The data enable assessment of the distribution of ergosterol and cholesterol in the amastigote stage of the parasite and its immediate surroundings in the vacuole. Proteophosphoglycans of parasite origin, an important hallmark of the infection, are identified throughout the PV.

SERS Probing of Proteins in Gold Nanoparticle Agglomerates

“…Estimating the amount of nanoparticles taken up by a typical cell (Drescher et al, 2012), and the number of typical-size gold nanoaggregates (Drescher et al, 2013b) that would fit in a focal volume, the number of particles is very similar. Since the most concentrated sample approximates the cellular protein concentration, the observed high SERS signals from live cells (Kneipp et al, 2006; Zivanovic et al, 2018) must be related to differences in the intracellular inhomogeneity of protein concentrations and to active transport processes, which facilitate the formation and positioning of aggregates in cellular compartments. Therefore, the combination of these phenomena can contribute to the SERS signal enhancement experienced in live cell SERS mapping.…”

Gold nanoisland substrates for SERS characterization of cultured cells

“…Other major protein-related vibrations were found at 823 cm −1 , 1002 cm −1 and 1304 cm −1 , representing a ring breathing mode of tyrosine, symmetric stretching of phenylalanine, and a component of the amide III band, respectively [50][51][52][53][54]. The band at 1278 cm −1 , assigned to an amide III vibration of proteins, but also to the symmetric stretching of PO 4 3− that can be attributed to phosphate groups contained in the phospholipids [50,55,56] has a significant presence in the Raman maps. The lipid-related vibrational modes are represented by bands at 418 cm −1 or 608 cm −1 of cholesterol, phospholipid alkyl chains at 1140 cm −1 , unsaturated fatty acids at 1270 cm −1 and CH 2 deformation in lipids at 1440 cm −1 [50,52,54,55,57].…”

X-ray tomography shows the varying three-dimensional morphology of gold nanoaggregates in the cellular ultrastructure

“…Understanding the interactions of nanomaterials, and in particular gold nanoparticles with molecules, cells, and tissues is required to achieve improvements in diagnostic imaging and in therapeutic applications. [1][2][3] In most cases, the quantity of particle uptake at the cellular level can be critical, for example in drug delivery or in radiotherapy. It is known that the physicochemical properties of nanomaterials, including their size, morphology, crystallinity, and surface modication, inuence their cellular uptake, distribution and interaction with the cell ultrastructure, and can lead to the intended theranostic result and/or cytotoxicity.…”