The new dual centrifuge "ZentriMix 380R" allows the safe, gentle and extremely simple preparation of small and uniform liposomes in closed vials. The so-called “in-vial homogenization” enables the preparation of sterile formulations with very high entrapping efficiencies (EE) for water-soluble substances. Since very small batches as well as 40 formulations can be prepared at once, the ZentriMix is an attractive screening tool for finding ideal lipid compositions and manufacturing conditions.
The use of the ZentriMix as a screening tool was investigated in a recently published study (https://www.mdpi.com/1999-4923/13/12/2046). For this purpose, dual centrifugation was combined with a simplified procedure to determine the EE-values. With the help of time-resolved fluorescence spectroscopy, it was possible to determine liposomally entrapped calcein without the time-consuming separation of the unentrapped marker. Fortunately, the new EE-determination can be performed with the same sample used to determine liposome size and size distribution (pdi), which further speeds up the screening process. In addition, differential scanning calorimetry (DSC) demonstrated that it is no longer necessary to prepare a molecularly dispersed lipid mixture (so-called lipid film) prior to the preparation of the liposomes; the lipids can simply be used as a macroscopic mixture. This not only saves valuable time, but also organic solvents. A complete screening of the manufacturing conditions of a lipid mixture is now possible in a normal working day (13 sample in triplicates or 40 samples in single determination). The screening results are summarized in a clear liposome screening diagram.