Measurement and visualization of cell membrane surface charge in fixed cultured cells related with cell morphology

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 positivelycharged 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.

Direct functionalization of cell‐adhesion promoters to hydrogel microparticles synthesized by stop‐flow lithography

“…As a model material representing cell‐adhesion promoter molecules in this study, we selected PLL, a synthetic cationic polymer that contains plenty amine groups in repeated monomers. We selected PLL as a model cell‐adhesion promoter because the positively charged PLL can electrostatically interact with cellular membranes since many different types of cells have negative surface charges 30 . Considering that there are highly abundant amine groups in the PLL structures, we induced the aza‐Michael addition reaction between electrophilic α,β‐unsaturated double bonds in the particles and nucleophilic nitrogen donor groups in the PLL (Figure 1B).…”

“…We selected PLL as a model cell-adhesion promoter because the positively charged PLL can electrostatically interact with cellular membranes since many different types of cells have negative surface charges. 30 Considering that there are highly abundant amine groups in the PLL structures, we induced the aza-Michael addition reaction between electrophilic α,β-unsaturated double bonds in the particles and nucleophilic nitrogen donor groups in the PLL (Figure 1B). 24,31 Among diverse acrylate-based conjugation chemistries, the aza-Michael addition reaction has distinct advantages, including commercial availability, no requirement for catalyst, and low productivity of reactive by-products during polymerization.…”

Monitoring Local pH of Membranous Aggregates via Ratiometric Color Changing Response

“…This might be due to differences in the intrinsic acidity of the polar head groups (À SO 3 À Na + vs. À CO 2 À Na + ). [20] Moreover, the interaction between probe molecules and the head groups of surfactants is expected to be more prominent in dynamic aggregates like micelles than that of observed in relatively ordered assemblies, like vesicles. [21] Further, to determine micropolarity around the probe molecules both in micelles and phospholipid vesicles, we have recorded fluorescence spectra of 1 in different dioxaneÀ water mixture medium.…”

Mapping Surface Charge Distribution of Single-Cell via Charged Nanoparticle

“…Therefore, it could be used as a marker for cell analysis and diagnostics. Recently, one paper has targeted the surface charge characteristics of cancer cells as novel biomarkers for cancer detection and treatments [ 2 ]. The variation of cell surface charge has also been reported for various types of stem cells during the differentiation process [ 3 ].…”