Biophysical properties of living cells largely determine their vital activity and functionality. In cancer, the physical state of the plasma membrane of cells is important for the invasion and metastasis. Cellular-scale viscoelasticity affects cell morphology, motility, interaction with the extracellular matrix, and resistance to mechanical stress. However, the links between membrane fluidity and cellular mechanics are poorly understood. Here, we present the in vitro study of microviscosity and viscoelastic properties of colorectal cancer cells. Measuring microviscosity of membranes at the micrometer scale was performed using fluorescence lifetime imaging microscopy FLIM with a viscosity sensitive probe. Atomic force microscopy AFM was used to evaluate the mechanical properties of cells. Additionally, the lipid profile of cells plasma membranes was analyzed using time-of-flight secondary ion mass spectrometry. A good positive correlation was found between cell stiffness (the Young’s modulus) and the plasma membrane microviscosity of cancer cells. Of the five cell lines, HT29 cells, which has an epithelial phenotype, had the most fluid membranes and the lowest stiffness values; the highest microviscosity and stiffness values were recorded for the SW480 cell line, which is characterized by a mesenchymal phenotype. The obtained results indicate that cell biomechanics is determined by the two sets of parameters that are interconnected in tumor cells and are involved in their migratory behavior.
We analyzed the structural and functional state of liver tissue in normal state and during regeneration using multiphoton microscopy in combination with the time-of-flight secondary ions mass spectrometry (TOF-SIMS). The induction of regeneration process was performed on 30% and 70% hepatectomy models of rats. The FLIM method has shown an increase in the contribution of the bound form of NADH, as well as the contribution of NADPH in hepatocytes, which indicates a growth in the contribution of oxidative phosphorylation and biosynetic processes during liver regeneration. Using the TOF-SIMS method, it has been shown that the signal from fragments of fats, fatty acids, phosphotidylcholine, and sphingomyelin is increased, combined with a decline in the signal from amino acid’s fragments in the regenerating liver. The results will make it possible to identify criteria for assessing the regenerative potential of the liver during resection in order to reduce the risk of developing of the postoperative liver failure.
Significance: Despite the importance of the cell membrane in regulation of drug activity, the influence of drug treatments on its physical properties is still poorly understood. The combination of fluorescence lifetime imaging microscopy (FLIM) with specific viscosity-sensitive fluorescent molecular rotors allows the quantification of membrane viscosity with high spatiotemporal resolution, down to the individual cell organelles.
Aim: The aim of our work was to analyze microviscosity of the plasma membrane of living cancer cells during chemotherapy with cisplatin using FLIM and correlate the observed changes with lipid composition and cell’s response to treatment.
Approach: FLIM together with viscosity-sensitive boron dipyrromethene-based fluorescent molecular rotor was used to map the fluidity of the cell’s membrane. Chemical analysis of membrane lipid composition was performed with time-of-flight secondary ion mass spectrometry (ToF-SIMS).
Results: We detected a significant steady increase in membrane viscosity in viable cancer cells, both in cell monolayers and tumor spheroids, upon prolonged treatment with cisplatin, as well as in cisplatin-adapted cell line. ToF-SIMS revealed correlative changes in lipid profile of cisplatin-treated cells.
Conclusions: These results suggest an involvement of membrane viscosity in the cell adaptation to the drug and in the acquisition of drug resistance.
Conventional techniques are insufficient to precisely describe the internal structure, heterogeneous cell populations and the dynamics of biological processes of the diseased liver during and after surgery. There is a need for a rapid and safe method for the successful diagnosis of liver disease to plan surgery, efficacy of regeneration and avoid postoperative liver failure. Here, we analyze acute and chronic liver pathology (cholestasis, cirrhosis, fatty liver disease) during progression by multiphoton microscopy with FLIM and SHG modes and chemical analysis by TOF-SIMS to obtain new data about hepatocyte pathological changes at the cellular and molecular level. All of these techniques enable to study cellular metabolism, lipid composition and collagen structure without sample staining and incorporation of fluorescent or another markers that may allow to use these methods in clinic. Complex of multiphoton microscopy and mass spectrometry provides complete information about the liver structure and function that could not be assessed using each method individually. The data can be used for both to obtain new criteria for the identification of hepatic pathology and to develop a rapid technique of liver quality analysis to plan surgery and avoid postoperative liver failure in clinic.
Conventional techniques are insufficient precisely to describe the internal structure, the heterogeneous cell populations, and the dynamics of biological processes occurring in diseased liver during surgery. There is a need for a rapid and safe method for the successful diagnosis of liver disease in order to plan surgery and to help avoid postoperative liver failure. We analyze the progression of both acute (cholestasis) and chronic (fibrosis) liver pathology using multiphoton microscopy with fluorescence lifetime imaging and second-harmonic generation modes combined with time-of-flight secondary ion mass spectrometry chemical analysis to obtain new data about pathological changes to hepatocytes at the cellular and molecular levels. All of these techniques allow the study of cellular metabolism, lipid composition, and collagen structure without staining the biological materials or the incorporation of fluorescent or other markers, enabling the use of these methods in a clinical situation. The combination of multiphoton microscopy and mass spectrometry provides more complete information about the liver structure and function than could be assessed using either method individually. The data can be used both to obtain new criteria for the identification of hepatic pathology and to develop a rapid technique for liver quality analysis in order to plan surgery and to help avoid postoperative liver failure in clinic.
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