Optical detection of cell-surface changes associated with malignant transformations in vitro

A need exists for new experimental approaches for the direct detection of cell-surface changes associated with malignant transformations. The usual methods of fractionating the cell to obtain plasma-membrane segments are disruptive and are influenced by uncertainties that frustrate most attempts to distinguish between the cell memebrane in the normal and malignant states. Here we describe a non-destructive microprobe technique using a light beam to monitor cell-surface changes in situ. Many investigations of tumor-cell behavior in culture are based on substrate-adherent populations of cells. By choosing the substrate to be optically dense and transparent, and by striking the substrate/cell interface by a light beam from the substrate side at an angle of incidence greater than the critical angle of total-internal reflection, an evanescent electromagnetic wave interacts with the peripheral zone of the substrate-adherent cells. Both the intensity and ellipse of polarization of the reflected wave can be monitored as the malignant transformation takes place, either chemically or virally. This technique should also provide new information concerning the molecular organization of the cell periphery from measurements on living cells.