Fast high-throughput screening of temoporfin-loaded liposomal formulations prepared by ethanol injection method

Abstract

A new strategy for fast, convenient high-throughput screening of liposomal formulations was developed, utilizing the automation of the so-called ethanol-injection method. This strategy was illustrated by the preparation and screening of the liposomal formulation library of a potent second-generation photosensitizer, temoporfin. Numerous liposomal formulations were efficiently prepared using a pipetting robot, followed by automated size characterization, using a dynamic light scattering plate reader. Incorporation efficiency of temoporfin and zeta potential were also detected in selected cases. To optimize the formulation, different parameters were investigated, including lipid types, lipid concentration in injected ethanol, ratio of ethanol to aqueous solution, ratio of drug to lipid, and the addition of functional phospholipid. Step-by-step small liposomes were prepared with high incorporation efficiency. At last, an optimized formulation was obtained for each lipid in the following condition: 36.4 mg·mL⁻¹ lipid, 13.1 mg·mL⁻¹ mPEG₂₀₀₀-DSPE, and 1:4 ethanol:buffer ratio. These liposomes were unilamellar spheres, with a diameter of approximately 50 nm, and were very stable for over 20 weeks. The results illustrate this approach to be promising for fast high-throughput screening of liposomal formulations.

Keywords::

• Liposome
• ethanol injection method
• temoporfin
• ethosome
• pipetting robot

Acknowledgments

The authors are grateful to biolitec AG for providing temoporfin and to Dipl. Ing. F. Steiniger for help with the Cryo-TEM measurement.

Declaration of interest

The “Thüringer Ministerium für Bildung, Wissenschaft und Kultur” (TMBWK; ProExcellence-Program NanoConSens, B514-09049) is gratefully acknowledged for generous financial support.