ABSTRACT
This chapter describes the characteristics of carboxyfluorescein (CF), the techniques for purifying it and encapsulating it in liposomes, and the methods for assaying its release. It provides examples of the use of Fluorescence Self-Quenching (FSQ) in three major categories: release of vesicle contents, liposome-cell interaction in vitro, and liposome stability in vivo. The FSQ method was initially developed to examine the interaction of liposomes with cells. Vesicles containing a high concentration of CF can be used to estimate release of vesicle contents into a cell, with relatively little interference from dye remaining in vesicles bound to the cell. CF is a highly water-soluble derivative of fluorescein. The methods for encapsulating CF are generally the same as those for other small hydrophilic solutes. The release of CF might be due to gradual leakage of dye from all of the vcsicles or to an all-or-none rupture of the permeability barrier in individual vesicles.
