Distribution of liposome-entrapped cations in tumor-bearing mice

Abstract

The effect of entrapment of 86Rb + and 22Na + in multilamellar, negatively charged phospholipid liposomes on their clearance from the bloodstream and uptake into a variety of tissues in tumor-bearing mice was studied. Although differences were seen between the distribution of free and entrapped ions, these were smaller than might be expected from the uptake of liposomes containing labelled phospholipid. One problem detected was that addition of mouse serum caused a large increase in the efflux of 22Na + from liposomes, suggesting that a large amount of the injected, trapped ions may have been free in the bloodstream within 1–2 hours. It is concluded that if liposomes are to be fully effective in increasing the uptake of entrapped substances into tissues, the type of liposome used as well as the nature of the entrapped substance are important variables.