Copper-topotecan complexation mediates drug accumulation into liposomes

Area of Science:

• Pharmaceutical Sciences
• Drug Delivery
• Nanotechnology

Background:

• Liposomal formulations enhance drug stability and delivery.
• Topotecan, a camptothecin derivative, is used in cancer therapy.
• Transition metal ions are explored for their role in drug encapsulation.

Purpose of the Study:

• To investigate the role of transition metal ions (Mn, Cu, Zn, Co) in the liposomal encapsulation of topotecan.
• To determine the optimal conditions for topotecan loading into liposomes.
• To characterize the interaction between copper and topotecan for formulation development.

Main Methods:

• Preparation of liposomes (DSPC:CH) with transition metal ion gradients.
• Encapsulation of topotecan into liposomes and measurement of drug loading.
• Characterization of copper-topotecan interactions in solution and liposomes using Cryo-TEM and pH studies.

Main Results:

• Zinc and cobalt ions did not facilitate topotecan loading.
• Manganese ions required a pH gradient and ionophore for minimal topotecan encapsulation.
• Copper ions efficiently encapsulated topotecan, irrespective of pH gradient, forming intravesicular precipitates.

Conclusions:

• Copper ion complexation is a viable method for preparing liposomal topotecan formulations.
• The active lactone form of topotecan is preferentially encapsulated via copper complexation.
• This approach offers a promising strategy for developing stable and effective liposomal camptothecin delivery systems.