Effect of Entrapped Markers on the in situ Jejunal Uptake from Liposomal Systems

The effect of entrapped PEG-4000, inulin, and insulin on the in situ uptake from the rat jejunum of liposomes was determined. Each of these markers greatly reduced or completely eliminated jejunal uptake unless the liposomes were repeatedly???washed??? to remove marker from the external bilayer surface. Addition of free marker to a suspension of empty liposomes resulted in complete loss of liposomal uptake. It appears that???inert??? markers can profoundly affect the rate and extent of liposomal uptake from the rat jejunum and the preparative technique employed can greatly affect the behavior of the system.