Influence of the surfactant concentration on the body distribution of nanoparticles

The rapid reticuloendothelial system (RES) uptake of nanoparticles after i. v. injection; especially by the liver, can be reduced and the body distribu tion can be altered by coating them with non-ionic surfactants. In the pres ent work 2-C-14-poly(methyl methacrylate) nanoparticles were coated with po loxamine 908 and polysorbate SO, and the influence of different surfactant concentrations on the body distribution was investigated. These surfactants were chosen because earlier studies showed that poloxamine 908 was very ef fective in decreasing the liver uptake and keeping the nanoparticles in cir culation, whereas polysorbate 80 was the most effective surfactant to direc t the particles to organs that do not belong to the RES. Above nanoparticle s were injected i.v. to rats and the animals were sacrificed after 30 min. Below a surfactant concentration of 0.1% the nanoparticle preparations beha ved like uncoated particles. At a 0.1% concentration a very sudden and sign ificant change in the body distribution occurred with poloxamine 908. The l iver concentration decreased from abo ut 75% of the dose to 13% and stayed at this level at higher surfactant concentrations. This decrease was combin ed with a similar sudden complementary increase in blood and other organ an d tissue concentrations. With polysorbate 80 the decrease in liver concentr ation and increase in the blood and the other organ levels was gradual and became important only above 0.5% surfactant concentration. The results indicate that the type of interaction and the strength of the a dsorptive binding to the nanoparticles are different with different surfact ants. This in turn leads to different body distribution patterns after i.v. injection of surfactant coated nanoparticles.