Caleosin-based nanoscale oil bodies for targeted delivery of hydrophobic anticancer drugs

Nanoscale artificial oil bodies (NOBs) could be assembled from plant oil, phospholipids (PLs), and oleosin (Ole) as previously reported. NOBs have a lipid-based structure that contains a central oil space enclosed by a monolayer of Ole-bound PLs. As an oil structural protein, Ole functions to maintain the integrity of NOBs. Like Ole, caleosin (Cal) is a plant oil-associated protein. In this study, we investigated the feasibility of NOBs assembled by Cal for targeted delivery of drugs. Cal was first fused with anti-HER2/neu affibody (ZH2), and the resulting fusion gene (Cal–ZH2) was then expressed in Escherichia coli. Consequently, NOBs assembled with the fusion protein were selectively internalized by HER2/neu-positive tumor cells. The internalization efficiency could reach as high as 90%. Furthermore, a hydrophobic anticancer drug, Camptothecin (CPT), was encapsulated into Cal-based NOBs. These CPT-loaded NOBs had a size around 200 nm and were resistant to hemolysis. Release of CPT from NOBs at the non-permissive condition followed a sustained and prolonged profile. After administration of the CPT formulation, Cal–ZH2-displayed NOBs exhibited a strong antitumor activity toward HER2/neu-positive cells both in vitro and in vivo. The result indicates the potential of Cal-based NOBs for targeted delivery of hydrophobic drugs.