The ability of tumor cells to migrate and invade adjacent tissue is a key property underlying the metastatic process. To ensure greater deformability and to facilitate movement, migratory cells undergo multiple changes in biophysical parameters, including those of stiffness and membrane viscosity. However, reports on correlations between cell motility and stiffness, or between cell motility and membrane microviscosity are rather limited and conflicting. Here, using atomic force microscopy (AFM) and fluorescence lifetime imaging (FLIM), we have investigated alterations in the mechanical properties of cancer cells and in the microviscosity of their plasma membranes that are associated with the migration process. It was found that upon activation of migration either through a "wound healing" test or by inducing epithelial-mesenchymal transition, human colorectal cancer cells undergo profound biomechanical remodeling characterized by simultaneous decreases in cell stiffness and in plasma membrane microviscosity. Our findings, therefore, support the results of previous studies that have shown cell softening and membrane fluidization to be critical adaptive responses enabling cell movement and that these can be regarded as potential biomarkers of tumor cell motility, offering scope for identifying new therapeutic targets.

The modifications in biomechanical properties of cells and tissue are important in cancer progression, including its different aspects, e.g. invasion, migration, adhesion, signaling, interactions with microenvironment, and immune response. However, our understanding of the changes in physical characteristics of cells, and especially the molecular basis for these changes, caused by malignant transformation remains rather limited. While the differences in stiffness and viscoelasticity of tumor and normal cells have been well documented at the cellular scale, subcellular and molecular alterations have been poorly characterised. In our work, we investigated the stiffness and viscoelastic parameters, mainly determined by the actin cortex, and the microviscosity of the plasma membrane, mainly determined by its lipid profile, in normal and cancer cells. The mechanical properties of the cells were assessed using atomic force microscopy (AFM). The microviscosity of the membrane was visualized by fluorescence lifetime imaging microscopy (FLIM) with the viscosity-sensitive probe BODIPY2. Chemical analysis of cell membranes was performed by secondary ion time-of-flight mass spectrometry (ToF-SIMS). The MCF-10 A (normal epithelial cells) and MCF-7 (human breast cancer) cell lines were used in the study. It was shown that cancer cells were more deformable due to a less organized and more isotropic filamentous structure of the actin cytoskeleton. At the same time they had more viscous plasma membranes, compared to normal cells, in both in vitro and tissue conditions. In the membrane lipid profile, increased signals of sphingomyelin and saturated fatty acids and decreased signals of polyunsaturated fatty acids were detected in cancer cells, which explain the higher microviscosity of their membranes. The obtained data indicate a complex reorganization of cell biomechanics at the cellular, subcellular and molecular levels during malignant transformation, which is important for better understanding of fundamental mechanisms of tumor development.

BACKGROUND: Methods for microbial inactivation, including physical approaches aimed at the destruction of biofilms formed by uropathogenic microorganisms for the prevention of infectious and inflammatory diseases in urology, remain insufficiently studied. The development of new strategies in this field remains relevant. AIM: To evaluate the feasibility of photodynamic inactivation of biofilms formed by typical representatives of uropathogenic microorganisms using an antiseptic agent with a bacteriostatic effect—methylene blue—possessing photochemical properties. METHODS: Cultures of Staphylococcus aureus and Escherichia coli isolated from renal calculi of patients from a urology department were used. In vitro experiments on photodynamic inactivation of microorganisms were conducted on mature preformed biofilms. Irradiation was performed using a diode laser emitting at a wavelength of 662 nm through a sterile 0.1% methylene blue solution in continuous mode across five setups (three control, two experimental). After irradiation, biofilms on the cover glasses were fixed on microscope slides using colorless varnish. The prepared specimens were stained with acridine orange solution, dried in the dark, examined under a fluorescence microscope at ×100 magnification using an immersion system, and photographed with a digital camera. Images were digitally processed using 3D modeling technologies with ImageJ software version 1.52a. RESULTS: The impact of the photoactive agent and laser irradiation was assessed at two power settings—450 mW and 1100 mW. In the first case, partial destruction of the biofilms was noted (41.9% of the original biofilm structure for S. aureus and 82.4% for E. coli), whereas in the second case, exposure at 1100 mW resulted in complete degradation of the mature multilayer biofilm into single cells without extracellular matrix, corresponding to 97.7% destruction of the original biofilm structure for S. aureus and 96.5% for E. coli. CONCLUSION: This study is the first to demonstrate the feasibility of photodynamic inactivation of uropathogenic biofilm-forming microorganisms using a photochemically active agent—methylene blue. The promising results suggest that combined laser irradiation and methylene blue application may serve as an alternative or adjunct to systemic antibiotic therapy in urological practice.

Introduction:Colorectal tumors have a close connection with the gut microbiome. A correlation between rearrangement in microbiome composition and disease progression has already been shown. However, the mechanisms underlying interactions between microorganisms and cancer cells, as well as the immediate effects of tumor-associated microbiomes on cancer cells, remain unclear. Materials & Methods:In this work, we investigated the effects of metabolites produced by tumor-associated Escherichia coli strains on the migration of human colorectal cancer cell lines (HCT116, SW480 and HT29). Results:We identified differences in some biochemical enzyme activity of E. coli strains and in the spectrum of synthesized organic acids between tumor-associated strains and the probiotic E. coli M-17 strains. Most strains associated with colorectal cancer were unable to utilize sucrose. Specifically, tumor-associated E. coli produced more fumaric, malic and maleic acids, whereas the E. coli M-17 produced more short-chain fatty acids such as propionic, 2-oxobutyric, and α-ketoglutaric acids (AKGs). Upon exposure to metabolites from tumor-associated E. coli strains, HCT116 and SW480 cells showed an increased migration activity, whereas HT29 cells showed decreased migration activity in both 2D and 3D culture models. Immunocytochemistry assay revealed a decrease in E-cadherin in HCT116 and SW480 cells and focal adhesion kinase (FAK)- in HT29, which explains the different effects of E. coli metabolites on migratory capacity of colorectal cancer cells. Conclusion:Therefore, these results suggest that the effect of tumor-associated E. coli strains on cancer cells migration depends on their innate type of migration and enhances FAK-dependent single-cell migration accompanied by the loss of E-cadherin in cancer cells with initially low FAK expression. In contrast, this effect was not observed in cancer cells exhibiting a collective migration phenotype.

The extracellular matrix (ECM), in which collagen is the most abundant protein, impacts many aspects of tumor physiology, including cellular metabolism and intracellular pH (pHi), as well as the efficacy of chemotherapy. Meanwhile, the role of collagen in differential cell responses to treatment within heterogeneous tumor environments remains poorly investigated. In the present study, we simultaneously monitored the changes in pHi and metabolism in living colorectal cancer cells in vitro upon treatment with a chemotherapeutic combination, FOLFOX (5-fluorouracil, oxaliplatin and leucovorin). The pHi was followed using the new pH-sensitive probe BC-Ga-Ir, working in the mode of phosphorescence lifetime imaging (PLIM), and metabolism was assessed from the autofluorescence of the metabolic cofactor NAD(P)H using fluorescence lifetime imaging (FLIM) with a two-photon laser scanning microscope. To model the ECM, 3D collagen-based hydrogels were used, and comparisons with conventional monolayer cells were made. It was found that FOLFOX treatment caused an early temporal intracellular acidification (reduction in pHi), followed by a shift to more alkaline values, and changed cellular metabolism to a more oxidative state. The presence of unstructured collagen markedly reduced the cytotoxic effects of FOLFOX, and delayed and diminished the pHi and metabolic responses. These results support the observation that collagen is a factor in the heterogeneous response of cancer cells to chemotherapy and a powerful regulator of their metabolic behavior.

Heterogeneity of tumor metabolism is an important, but still poorly understood aspect of tumor biology. Present work is focused on the visualization and quantification of cellular metabolic heterogeneity of colorectal cancer using fluorescence lifetime imaging (FLIM) of redox cofactor NAD(P)H. FLIM-microscopy of NAD(P)H was performed in vitro in four cancer cell lines (HT29, HCT116, CaCo2 and CT26), in vivo in the four types of colorectal tumors in mice and ex vivo in patients’ tumor samples. The dispersion and bimodality of the decay parameters were evaluated to quantify the intercellular metabolic heterogeneity. Our results demonstrate that patients’ colorectal tumors have significantly higher heterogeneity of energy metabolism compared with cultured cells and tumor xenografts, which was displayed as a wider and frequently bimodal distribution of a contribution of a free (glycolytic) fraction of NAD(P)H within a sample. Among patients’ tumors, the dispersion was larger in the high-grade and early stage ones, without, however, any association with bimodality. These results indicate that cell-level metabolic heterogeneity assessed from NAD(P)H FLIM has a potential to become a clinical prognostic factor.

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.

This work was aimed at the complex analysis of the metabolic and oxygen statuses of tumors in vivo after photodynamic therapy (PDT). Studies were conducted on mouse tumor model using two types of photosensitizers—chlorin e6-based drug Photoditazine predominantly targeted to the vasculature and genetically encoded photosensitizer KillerRed targeted to the chromatin. Metabolism of tumor cells was assessed by the fluorescence lifetime of the metabolic redox-cofactor NAD(P)H, using fluorescence lifetime imaging. Oxygen content was assessed using phosphorescence lifetime macro-imaging with an oxygen-sensitive probe. For visualization of the perfused microvasculature, an optical coherence tomography-based angiography was used. It was found that PDT induces different alterations in cellular metabolism, depending on the degree of oxygen depletion. Moderate decrease in oxygen in the case of KillerRed was accompanied by an increase in the fraction of free NAD(P)H, an indicator of glycolytic switch, early after the treatment. Severe hypoxia after PDT with Photoditazine resulted from a vascular shutdown yielded in a persistent increase in protein-bound (mitochondrial) fraction of NAD(P)H. These findings improve our understanding of physiological mechanisms of PDT in cellular and vascular modes and can be useful to develop new approaches to monitoring its efficacy.

Resistance to chemotherapy remains the main challenge for cancer treatment. One of the mechanisms of tumor escape from cytotoxic agents could be the formation of cell-in-cell (CIC) structures, in which the outer cell protects the inner cell from unfavorable environment. Such structures have been found in many tumor types, however, their link to chemosensitivity is elusive. Here, we tested whether the CIC structures can promote resistance of colorectal cancer cells to chemotherapy. To identify CIC structures in cell cultures and in tumor xenografts, both transmission electron microscopy and confocal fluorescence microscopy of live and fixed cells as well as tissue slices and histopathology were used. Cytogenetic analysis was performed to detect chromosome instability associated with the drug resistance. It was found that in the five colorectal cancer cell lines intrinsic chemoresistance positively correlated with the ability of cells to spontaneously form CIC structures. Cultured cells treated with oxaliplatin and Irinotecan and tumor xenografts treated with FOLFOX or FOLFIRI regimens displayed an increased number of CICs after the treatment. The release of the inner cell from CIC structure was observed after removal of the drug. The number of CICs in the cell lines and tumors with acquired resistance to oxaliplatin was higher than in the drug-naive counterparts. The development of chemoresistance was also accompanied by the changes in the cell’s ploidy. These preliminary data clearly demonstrate the associations of CIC structures with chemoresistance of colorectal cancer in cultured cells and tumor xenografts and show the prospect of further clinical validation of CICs as a potential prognostic marker for treatment efficiency.

Boron neutron capture therapy (BNCT), due to its high biological efficiency, is one of the most promising methods of radiation therapy for malignant tumors. Currently, research in this area has received momentum due to the emergence of fundamentally new compact neutron sources suitable for clinical use. The aim of the investigation was to study L-boronphenylalanine (L-BPA) biodistribution in the organs of experimental animals with subcutaneous tumor xenografts, and evaluate the application of the experimental model to assess the effectiveness of new neutron sources. Materials and Methods. The experiments were carried out on BALB/c mice with subcutaneous xenograft of mouse adenocarcinoma CT26. L-boronphenylalanine in a molar excess of fructose was administered intravenously at a dose of 350 mg/kg, the organs under study were taken 1.5, 3, 6, and 24 h after drug administration. The content of the B-10 isotope was analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The absence of toxic effects was verified pathomorphologically. Results. The maximum L-BPA content in the tumor was 142.0 +/- 4.41 mu g/g 1.5 h after drug administration. The minimum therapeutic concentration of L-BPA in the tumor persists up to 5.4 h after drug administration. Among normal organs, the maximum content was observed in the kidneys, it is most likely being associated with the structural and functional features of the organ rather than the true content of L-BPA in the tissues. Histological studies revealed no structural disorders and dystrophic changes in tissues against the background of L-BPA introduction. Conclusion. The results of the study demonstrate the feasibility of the studied tumor model to evaluate the efficiency of new neutron sources for BNCT. The L-borophenylalanine content in the tumor and the time of maintaining the minimum therapeutic concentration appeared to be sufficient for effective BNCT. The high contrast of 10B accumulation relative to non-pathological tissues minimizes the possible side effects of BNCT.

Antimicrobial photodynamic therapy (aPDT) was demonstrated to be effective against various species of Gram-positive bacteria. However, the complex structure of a Gram-negative bacteria envelope limits the application of aPDT. Thus, the goal of this study was to improve the efficiency of antimicrobial photodynamic therapy with Fotoditazin against uropathogenic Gram-negative bacteria. The non-ionic detergent Triton X-100 and emulsifier Tween 80 were tested. The effect of extracellular photosensitizer on aPDT efficacy was analyzed. Moreover, the irradiation regime was optimized in terms of the output power and emitting mode. It was found that Triton X-100 at 10% vol enhanced the efficacy of aPDT of E. coli up to 52%. The subsequent observation demonstrated that, when the photosensitizer was removed from the extracellular space, the efficacy of aPDT on various Gram-negative species decreased dramatically. As for the irradiation mode, an increase in the laser output power led to an increase in the aPDT efficacy. The pulsed irradiation mode did not affect the aPDT efficacy. Thus, in order to achieve optimal aPDT efficacy, bacteria should be irradiated at 450-mW output power in the presence of Triton X-100 and a photosensitizer in the extracellular environment. However, it should be noted that the efficacy of aPDT of K. pneumoniae was significantly lower than for other species. The developed aPDT technique may be effective in a native environment of uropathogenic microorganisms.

Urinary tract infection (UTIs) aremainly caused by a number of anatomical and physiological dysfunctions, but there are also some iatrogenic factors, including the use of certain medications, that contribute to the development of UTIs. The virulence of bacteria that colonize the urinary tract may be modified by pH and by the presence of soluble substances in urine, such as norepinephrine (NE) and glucose. In this work, we studied the influence of NE and glucose across a range of pHs (5, 7, 8) on the biomass, matrix production and metabolism of uropathogenic strains of Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and Enterococcus faecalis. We used Congo red and gentian violet to stain the extracellular matrix and biomass, respectively, of biofilms. The optical density of staining of the biofilms was measured using a multichannel spectrophotometer. The metabolic activity was analyzed by MTT assay. It was shown that NE and glucose stimulate biomass production both in the Gram-negative and Gram-positive uropathogens. The metabolic activity in the presence of glucose was higher at pH 5 for E. coli (in 4.0 ± 0.1 times), Ps. aeruginosa (in 8.2 ± 0.2 times) and Kl. pneumoniae (in 4.1 ± 0.2 times). Matrix production of Kl. pneumoniae increased under NE (in 8.2 ± 0.2 times) and in the presence of glucose (in 1.5 ± 0.3 times). Thus, NE and glucose in urine may lead to persistent UTI under patient stress and in the case of metabolic glucose disorders.

The cell membrane is an important regulator for the cytotoxicity of chemotherapeutic agents. However, the biochemical and biophysical effects that occur in the membrane under the action of chemotherapy drugs are not fully described. In the present study, changes in the microviscosity of membranes of living HeLa–Kyoto tumor cells were studied during chemotherapy with paclitaxel, a widely used antimicrotubule agent. To visualize the microviscosity of the membranes, fluorescence lifetime imaging microscopy (FLIM) with a BODIPY 2 fluorescent molecular rotor was used. The lipid profile of the membranes was assessed using time-of-flight secondary ion mass spectrometry ToF-SIMS. A significant, steady-state decrease in the microviscosity of membranes, both in cell monolayers and in tumor spheroids, was revealed after the treatment. Mass spectrometry showed an increase in the unsaturated fatty acid content in treated cell membranes, which may explain, at least partially, their low microviscosity. These results indicate the involvement of membrane microviscosity in the response of tumor cells to paclitaxel treatment.

The biophysical properties of cells described at the level of whole cells or their membranes have many consequences for their biological behavior. However, our understanding of the relationships between mechanical parameters at the level of cell (stiffness, viscoelasticity) and at the level of the plasma membrane (fluidity) remains quite limited, especially in the context of pathologies, such as cancer. Here, we investigated the correlations between cells’ stiffness and viscoelastic parameters, mainly determined via the actin cortex, and plasma membrane microviscosity, mainly determined via its lipid profile, in cancer cells, as these are the keys to their migratory capacity. The mechanical properties of cells were assessed using atomic force microscopy (AFM). The microviscosity of membranes was visualized using fluorescence-lifetime imaging microscopy (FLIM) with the viscosity-sensitive probe BODIPY 2. Measurements were performed for five human colorectal cancer cell lines that have different migratory activity (HT29, Caco-2, HCT116, SW 837, and SW 480) and their chemoresistant counterparts. The actin cytoskeleton and the membrane lipid composition were also analyzed to verify the results. The cell stiffness (Young’s modulus), measured via AFM, correlated well (Pearson r = 0.93) with membrane microviscosity, measured via FLIM, and both metrics were elevated in more motile cells. The associations between stiffness and microviscosity were preserved upon acquisition of chemoresistance to one of two chemotherapeutic drugs. These data clearly indicate that mechanical parameters, determined by two different cellular structures, are interconnected in cells and play a role in their intrinsic migratory potential.

This review summarizes information about cell-in-cell (CIC) structures with a focus on gastrointestinal tumors. The phenomenon when one cell lives in another one has attracted an attention of researchers over the past decades. We briefly discuss types of CIC structures and mechanisms of its formation, as well as the biological basis and consequences of the cell-engulfing process. Numerous clinico-histopathological studies demonstrate the significance of these structures as prognostic factors, mainly correlated with negative prognosis. The presence of CIC structures has been identified in all gastrointestinal tumors. However, the majority of studies concern pancreatic cancer. In this field, in addition to the assessment of the prognostic markers, the attempts to manipulate the ability of cells to form CISs have been done in order to stimulate the death of the inner cell. Number of CIC structures also correlates with genetic features for some gastrointestinal tu-mors. The role of CIC structures in the responses of tumors to therapies, both chemotherapy and immunotherapy, seems to be the most poorly studied. However, there is some evidence of involvement of CIC structures in treatment failure. Here, we summarized the current literature on CIC structures in cancer with a focus on gastrointestinal tumors and specified future perspectives for investigation.

The 'dusting' technique of lithotripsy for the removal of infected urinary calculi and the wide use of drainage after endoscopic surgery may stimulate spreading of multidrug-resistant bacterial strains. Antibacterial photodynamic therapy (PDT) is one promising method for the elimination these strains. The purpose of our study was to evaluate alterations of renal pelvis morphology and renal function in laboratory animals after bactericidal regimens of PDT. Renal pelvises of pigs were filled with Photoditazine and then assessed either by examining the accumulation of Photoditazine in the urothelium or by illumination with a laser at a wavelength of 662 nm. A renal test and a complete blood count was performed to assess a negative effect of the treatment on health. Structural alterations of the kidney tissues were analyzed by histological examination. No photosensitizer fluorescence was detected in the urothelium of the pelvis. Histological study showed that PDT caused minor changes to the urothelium of the renal pelvis but did not affect the underlying connective tissue. No renal function abnormalities were found after PDT. Thus, the study indicates that antibacterial PDT is a safety technique that can complement common antibiotic therapy in the surgical treatment of urolithiasis.

Introduction. Secreted metabolites with enzymatic or toxic properties are important for effecting of Candida spp pathogenicity. The most clinically significant species is C. albicans. However, invasive infections associated with C. auris have a great significance. The aim of the investigation is comparison the some of enzymatic properties and biocidal activity of C. auris with those of C. albicans. Materials and methods. C. albicans and C. auris strains were used in the study. Growth of micromycetes was detected on nutrient agar, Sabouraud agar or blood agar (with hemolysis presence). The Candida spp. proteinase activity was determined on Difco agar with 2% casein and by cleavage of IgG molecules. Candida lipase activity was assessed on the agar with Tween-20. The viability of buccal epithelial cells after exposure (1 4 h) with candida metabolites was estimated by trypan blue assay. Statistical analysis was performed using RStudio software. Results. The best growth of C. albicans was observed on Sabouraud agar, and C. auris on blood agar. Only C. auris had hemolytic and lipase activity. Protease activity of some C. auris strains was noted. They were able to cleave casein and damage IgG molecules. The metabolites of some Candida strains decreased the viability of epithelial cells while the reduction was more pronounced in the experiments with C. auris (р 0.05). Conclusion. The most suitable medium for C. auris culturing was blood agar. Proteolytic, antiglobulin, hemolytic and lipase activities were observed only for C. auris. C. auris demonstrated more invasive capacity compared to C. albicans. The observed micromycete biocidal activity against buccal epithelial cells was strain-dependent.

In this work we studied nanoceria (CeO2NPs) and nanoceria modified by 5-fluorouracil (5FU) as potential APIs. Nanoceria were synthesized by precipitation in a matrix of hydroxyethyl cellulose or hydroxypropylmethyl cellulose, using cerium (III) nitrate and meglumine. Nanoceria properties were estimated by UV, FTIR and X-ray photoelectron spectra; scanning electron and atomic force microscopy; powder X-ray diffraction patterns and energy dispersive X-ray microanalysis. The cytotoxicity of nanoceria and polymer-protected nanoparticles was evaluated using the established cell line NCTC clone 929 (C3H/An mouse, subcutaneous connective tissue, clone of L. line). The morphology and metabolic activity of nanoparticles at 10 μg∙mL−1 of cells was not significant. In addition, the cytotoxic effects of nanoceria were assessed on two human colorectal cancer cell lines (HT29 and HCT116), murine melanoma B16 cells and normal human skin fibroblasts. An inhibitory effect was shown for HCT116 human colorectal cancer cells. The IC50 values for pure CeO2NPs and CeO2NPs-5FU were 219.0 ± 45.6 μg∙mL−1 and 89.2 ± 14.0 μg∙mL−1, respectively. On the other hand, the IC50 of 5FU in the combination of CeO2NPs-5FU was 2-fold higher than that of pure 5FU, amounting to 5.0 nmol∙mL−1. New compositions of nanoceria modified by 5-fluorouracil in a polymer matrix were designed as a dermal polymer film and gel. The permeability of the components was studied using a Franz cell.

Due to the prevalence of postoperative complications in the treatment of urolithiasis, the study of the contamination of urinary calculi and the potential pathogenicity of isolated bacteria is of great importance in laboratory diagnostic practice. It has been shown that uropathogenic bacteria are found in the composition of urinary stones in 65±7.1% of cases, mainly representatives of the Enterobacteriaceae and Staphylococcaceae families. Bacteria of the generas Escherichia, Enterococcus, Staphylococcus were most frequently detected. The analysis of biofilm activity and antibiotic resistance in 50 uropathogenic strains was carried out. It was shown that all the studied strains were resistant to at least two tested drugs, and the average value of the multiple resistance index was 0.51. When cultured on nutrient agar with Congo red, it was shown that more than half of the tested strains have high biofilm activity and about 80% potential for biofilm formation. The greatest biofilm activity was observed in bacteria of the generas Escherichia, Klebsiella, Enterobacter, Staphylococcus.

The investigations reported here were designed to determine whether the bulk plasma membrane is involved in mechanisms of acquired resistance of colorectal cancer cells to 5-fluorouracil (5-FU). Fluorescence lifetime imaging microscopy (FLIM) of live cultured cells stained with viscosity-sensitive probe BODIPY 2 was exploited to non-invasively assess viscosity in the course of treatment and adaptation to the drug. In parallel, lipid composition of membranes was examined with the time-of-flight secondary ion mass spectrometry (ToF-SIMS). Our results showed that a single treatment with 5-FU induced only temporal changes of viscosity in 5-FU sensitive cells immediately after adding the drug. Acquisition of chemoresistance was accompanied by persistent increase of viscosity, which was preserved upon treatment without any changes. Lipidomic analysis revealed that the resistant cells had a lower level of monounsaturated fatty acids and increased sphingomyelin or decreased phosphatidylcholine in their membranes, which partly explain increase of the viscosity. Thus, we propose that a high membrane viscosity mediates the acquisition of resistance to 5-FU.