Application of99mTc Labeling for Fast Comparative Screening of Preformed Liposomes in vivo

Labeling of preformed liposomes with 99mTc is a simple, quick, and highly versatile method, and its potential in the comparative screening of preformed liposomes with regard to their early biodistribution properties, such as the BLOOD/RES ratios at 2 and 30 min postadministration, was investigated. Liposomes differing in lipid composition and size were prepared and labeled under optimum conditions with 99mTc using a slight modijication of a previously described method (1). The amount of SnCl2 used to reduce pertechnetate affected liposome biodistribution. The labeling method employed was capable of detecting anticipated changes in liposome biodistribution caused by alterations in liposome composition or size. It could also reveal the effect of a relative immiscibility of monosialganglioside GM1 with di-myristoy1-phosphatidyl-choline:di-myristoyl-phosphatidyl-glycerol (DMPC:DMPG) on the biodistribution of DMPC:DMPG:GM, liposomes. It is proposed that 99mTc labeling of liposomes provides a tool for fast comparative screening of preformed liposomal preparations according to their early biodistribution.