The atomic force microscope is broadly used to study the morphology of cells1–5 but it can also probe the mechanics of cells. It is now known that cancerous cells may have different mechanical properties than normal cells6–8 but the reasons for these differences are poorly understood9. Here we report quantitatively the differences between normal and cancerous human cervical epithelial cells by considering the brush layer on the cell surface. These brush layers, which consist mostly of microvilli, microridges, and cilia are important for interacting with the environment. Deformation force curves obtained from cells in vitro are processed according to the 'brush on soft cell model 10. We found that normal cells have brushes with one length while cancerous cells displayed long and short brushes with significantly different densities. The observed differences suggest that brush layers should be taken into account when characterizing the cell surface by mechanical means.
Observation of a brush on the cell surface with the atomic force microscopy ͑AFM͒ in vitro is reported. The number of methods to study brushes that coat living cells is limited despite their biological importance. Moreover, it is important to take into account the brush layer when studying cell mechanics. Here the authors present an AFM method to detect the length and grafting density of the brush on viable cells with resolution that considerably surpasses any existing method. The authors demonstrate this method using cultured human cervical epithelial cells, but it can be applied to any type of cell.
To date, the methods of detection of cancer cells have been mostly based on traditional techniques used in biology, such as visual identification of malignant changes, cell growth analysis, specific ligand-receptor labeling, or genetic tests. Despite being well developed, these methods are either insufficiently accurate or require a lengthy complicated analysis. A search for alternative methods for the detection of cancer cells may be a fruitful approach. Here we proposed a novel method for detection of cancer cells in vitro, which is based on non-specific adhesion of silica beads to cells. First, we use atomic force microscopy (AFM) to study adhesion of single silica beads to malignant and normal cells cultured from human cervix. We found that adhesion depends on the time of contact, and can be statistically different for malignant and normal cells. Using these data, we develop an optical method utilizing fluorescent silica beads. The method is based on the detection of difference in the number of adherent particles. The method has been tested using primary cells cultured from cervical tissues of three healthy individuals and three patients with cervical cancer. The method shows sufficiently high sensitivity for cancer to make it interesting to perform further statistical tests.
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