Absorption of 10-hydroxycamptothecin into the coat of magnetoliposomes

The work deals with the binding of 10-hydroxycamptothecin (HCPT) in the coating of so-called magnetoliposomes (MLs). The latter consist of nanometer-sized crystalline magnetite (Fe3O4) cores surrounded by a phospholipid bilayer, which for the present study is built up of either dipalmitoylphosphatidylcholine (DPPC) or mixtures of DPPC with dipalmitoylphosphatidylglycerol (DPPG) (DPPC/DPPG molar ratios of 4/1, 2/1, 1/1 and 1/3). Partitioning of HCPT in the ML coat significantly improves as the DPPG content in the ML coat increases, suggesting the importance of H-bridges between DPPG and HCPT in the absorption process. In contrast to the behaviour of ‘classical’ phospholipid membranes which expand upon drug binding, it is calculated that with the phospholipid bilayer immobilized on the Fe3O4 surface 2.6 ± 0.5 phospholipid molecules have to leave the membrane for insertion of 1 HCPT molecule. The potential of the ML-drug structures as promising theranostics (i.e. nanocolloids with both therapeutic and diagnostic features) is briefly discussed.