Preparation, characterisation and biodistribution of 99mTc-labeled liposome encapsulated cyclosporine

The present study investigated the effect of charge (neutral, negative and positive) on liposomal membrane on the distribution of cyclosporine encapsulated in it to various organs. Liposomes were prepared by using different phospholipids by thin film hydration followed by sequential extrusion through polycarbonate membranes to achieve a desired particle size, with high entrapment efficiency and then lyophilised using sucrose as cryoprotectant. The possible in vivo distribution of cyclosporine and its liposomes after direct labeling with reduced technetium-99m has been studied in mice. The blood kinetics and biodistribution study of these labeled complexes shows prolonged circulation of positive and neutral charged liposomes in blood compared to free drug and negative charged liposomal formulation. The biodistribution of the tagged liposomes confirms that increased radioactivity was seen in liver and spleen, with minimal involvement of the kidney. At 4 h post injection the biodistribution data in kidney reveals approximately 1-2% of the injected dose was present for cyclosporine loaded liposomes, which elicits the possibility of reducing the nephrotoxicity, generally seen in free cyclosporine. Interestingly, the biodistribution and gamma imaging studies of the charged cyclosporine liposomes indicated that an appreciable amount of these labeled complexes goes to bone marrow when compared to the free cyclosporine. The findings demonstrate the distribution of these liposomes within various organs and proved that the positively charged liposomes experience increased bone uptake and prolonged circulation half-life. Hence this finding implies the possibility of using these formulations for liver and bone marrow transplantation.