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Mapping pH at Cancer Cell Surfaces
Da Wei1, Donald M Engelman2, Yana K Reshetnyak1
1Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI, 02874, USA.
Purpose:
To develop a tool to measure the pH at the surfaces of individual cells.
Procedures:
The SNARF pH-sensitive dye was conjugated to a pHLIP® peptide (pH-Low Insertion Peptide) that binds cellular membranes in tumor spheroids. A beam splitter allows simultaneous recording of two images (580 and 640 nm) by a CCD camera. The ratio of the two images is converted into a pH map resolving single spheroid cells. An average pH for each cell is calculated and a pH histogram is derived.
Results:
Surface pH depends on cellular glycolytic activity, which was varied by adding glucose or deoxy-glucose. Glucose was found to decrease the surface pH relative to the pH of the bulk solution. The surface pH of metastatic cancer cells was lower than that of non-metastatic cells indicating a higher glycolytic activity.
Conclusions:
Our method allows cell surface pH measurement and its correlation with cellular glycolytic activity.
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