Optical and electron microscopy imaging of model circulating tumour cells
Abstract
Background: Microscopy is a key tool in biophysical research for visualizing living cells' morphology, structure, and dynamic processes. Depending on the specific research goals, various optical and electron microscopy techniques can be applied, each offering unique benefits. Determining the structural features of the cytoskeleton, nucleus, and membrane of circulating tumor cells in the model Lewis lung carcinoma (LLC) is an important biophysical and biological task, as it will allow identifying targets for antitumor and antimetastatic therapy, as well as investigating the mechanisms of action of antitumor drugs. However, comprehensive multimodal imaging of such cells — particularly under non-adherent conditions — remains limited in the literature due to the difficulty of working with such models.
Objectives: This study aimed to visualize Lewis lung carcinoma (LLC) cells cultured under de-adhesive conditions using various microscopy techniques for their characterization and to examine the cancer cells' structure and functionality. The goal was to evaluate each method's individual capabilities and combined strengths in revealing cellular morphology, internal structure, and nanoparticle interactions.
Materials and Methods: LLC cells were obtained from the National Bank of Cell Lines and Tumor Strains of the IEPOR (NAS of Ukraine) and cultured in RPMI-1640 medium under conditions of de-adhesive growth. Imaging was performed using inverted optical microscopy (Euromex Oxion), fluorescence and confocal microscopy (Carl Zeiss LSM 510) with F-actin (Alexa Fluor 488-phalloidin) and nuclear (Hoechst 33342) staining, and label-free Coherent Anti-Stokes Raman Scattering (CARS) microscopy (Leica TCS SP8). Scanning electron microscopy (TESCAN MIRA3 LMU) was used for high-resolution surface imaging. 2D-MoS₂ nanoparticles, as well as 2D-MoS₂ and doxorubicin simultaneously, were applied to investigate nanoparticle-mediated labeling and cellular uptake.
Results: A comparative analysis of multiple imaging modalities — including optical, fluorescence, confocal, CARS, and SEM — was applied to Lewis lung carcinoma (LLC) cells. Fluorescence microscopy with specific fluorophores made it possible to analyze the size and properties of actin fibers and showed that nuclei occupy most of the deadhesive cells. Electron microscopy revealed numerous filopodia on the cell surface. CARS showed the presence of lipid droplets in the cells.
Conclusions: Each microscopy method provided complementary insights into cell morphology, cytoskeletal organization, lipid content, and surface ultrastructure. Nanoparticles demonstrated high utility as dual imaging and therapeutic agents. This work represents the first detailed SEM study of non-adherent LLC cells and highlights the potential of integrated multimodal imaging for studying circulating tumor cell models.
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Copyright (c) 2025 M. Olenchuk, G. Monastyrskyi, O. Gnatyuk, А. Boisen, Z. Zhang, G. Solyanik, D. Kolesnyk, S. Karakhim, G. Dovbeshko
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