Protein clustering in chemically stressed HeLa cells studied by infrared nanospectroscopy

Abstract

Photo-Thermal Induced Resonance (PTIR) nanospectroscopy, tuned towards amide-I absorption, was used to study the distribution of proteic material in 34 different HeLa cells, of which 18 were chemically stressed by oxidative stress with NaAsO. The cell nucleus was found to provide a weaker amide-I signal than the surrounding cytoplasm, while the strongest PTIR signal comes from the perinuclear region. AFM topography shows that the cells exposed to oxidative stress undergo a volume reduction with respect to the control cells, through an accumulation of the proteic material around and above the nucleus. This is confirmed by the PTIR maps of the cytoplasm, where the pixels providing a high amide-I signal were identified with a space resolution of ∼300 × 300 nm. By analyzing their distribution with two different statistical procedures we found that the probability to find protein clusters smaller than 0.6 μm in the cytoplasm of stressed HeLa cells is higher by 35% than in the control cells. These results indicate that it is possible to study proteic clustering within single cells by label-free optical nanospectroscopy.

Identification of Oxidative Stress in Red Blood Cells with Nanoscale Chemical Resolution by Infrared Nanospectroscopy

“…The system enables the simultaneous measurement of conventional morphology and the mapping of chemical and mechanical properties of the samples. RBCs are ideally suited for AFM-IR studies since, when dehydrated, their height is generally smaller than 1–1.3 µm, thus allowing a regime of linearity of the IR signal as a function of the thickness of the sample and of the intensity of the laser, which was kept constant for all the measurements [ 29 , 44 ]. This enables the study of the chemical heterogeneity of individual cells in the acquired IR maps at fixed wavenumber.…”

Gold Nanoparticles in Single-Cell Analysis for Surface Enhanced Raman Scattering

“…In another approach, the conductivity of cells is used to analyze the cellular response [103,104]. A label-free protein foci formation analysis on oxidatively stressed HeLa cells was recently accomplished by utilizing infrared nanospectroscopy [105]. In most of the above-mentioned approaches, one property of a cell or information from a certain location of the cell is obtained at a time.…”

Nanoscale partitioning of paclitaxel in hybrid lipid–polymer membranes

“…19,20 The PTIR mechanical detection scheme, works in principle at all wavelengths and its operating range has been recently extended from the mid-IR to the visible. 25,26 PTIR’s working principles 16,17 and its applications in photovoltaics, 27,28 polymer science, 29–32 pharmaceutics, 33,34 plasmonics, 35–37 2D materials, 38,39 medicine, 40,41 biology, 40,42 geology 43 have been reviewed recently. For example, PTIR has been applied to study the nanoscale distribution of drug-polymer blends 33,34 and to study the trans-membrane protein conformation in purple bacterial membranes.…”