where CF is a flux of the permeating substance, erm,CF is its permeability, and liposome,CF is the mass concentration of CF inside the liposomes. The previously mentioned t,CF was calculated using the calibration curve from the measured fluorescence intensity over time. The unknown quantity liposome,CF , was obtained from the mass balance, considering that the total quantity of CF, which is known, is present in the liposomal lumen, in the membrane, in the bulk outside liposomes. We start with the basic expression: