Abstract
The diagnosis of patients with malignancies relies on the results of a clinical cytological examination. To enhance the diagnostic qualities of cytological examinations, it is important to have a detailed analysis of the cell’s characteristics. There is, therefore, a need for developing a new auxiliary method for cytological diagnosis. In this study, we focused on studying the charge of the cell membrane surface of fixed cells, which is one of important cell’s characteristics. Although fixed cells lose membrane potential which is observed in living cells owing to ion dynamics, we hypothesized that fixed cells still have a cell membrane surface charge due to cell membrane components and structure. We used 5 cell lines in this study (ARO, C32TG, RT4, TK, UM-UC-14). After fixation with CytoRich Red, we measured the cell membrane surface charge of fixed cells in solution using zeta potential measurements and fixed cells on glass slides, visualizing it using antibody-labeled beads and positively-charged beads. Furthermore, we measured the cell membrane surface charge of fixed cells under different conditions, such as different solution of fixative, ion concentration, pH, and pepsin treatments. The zeta potential measurements and visualization using the beads indicated that the cell membrane surface of fixed cells was negatively charged, and also that the charge varied among fixed cells. The charge state was affected by the different treatments. Moreover, the number of cell-bound beads was small in interphase, anaphase, and apoptotic cells. We concluded that the negative cell membrane surface charge was influenced by the three-dimensional structure of proteins as well as the different types of amino acids and lipids on the cell membrane. Thus, cell surface charge visualization can be applied as a new auxiliary method for clinical cytological diagnosis. This is the first systematic report of the cell membrane surface charge of fixed cells.
Highlights
The diagnosis of patients with malignancies relies on the results of a cytological examination, which constitutes the most important part of the patients’ clinical examination
Cell proliferation in cancer is associated with a high membrane potential in living cells due to activation of potassium ion channels [14, 15]
It has been confirmed that the membrane potential of living cells involves various cellular biological activities [17,18,19,20]
Summary
The diagnosis of patients with malignancies relies on the results of a cytological examination, which constitutes the most important part of the patients’ clinical examination. Cell membrane surface charge in fixed cells examination of cytology specimens distinguishes between benign and malignant cells, based on the presence of cellular atypia such as irregular cell shape, abnormal cytoplasm, nuclear swelling with irregular contour and hyperchromatism [1]. These biological cellular characteristics are important, the cell membrane surface, which has been so far overlooked, may be a part of the abnormal cytological findings in a cytological examination. The cell membrane surface is important for cell adhesion, function, differentiation, and cell division
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