Use of supercritical CO2 for the production and sterilization of liposomes

Liposome sterilization as well as their industrial manufacturing remain a challenge. Indeed, conventional sterilization methods induce physicochemical deteriorations of liposomes or involve flammable and explosive gazes that can generate toxic residues [1]. Regarding liposome production, conventional methods have limitations such as small batch size, high difficulty in scaling up the product, and the use of high volume of organic solvents. Moreover, all these methods involve multiple steps and suffer from poor reproducibility [2-5].
This study aims to assess the potential use of supercritical carbon dioxide (ScCO2) for both production and sterilization of liposomes in a single step.
RESULTS AND DISCUSSION
A response surface A-optimal experimental design was constructed using JMP Pro 15 software (SAS Institute, Cary, USA) to test the main effects of the selected continuous process parameters: temperature (40°C to 80°C), pressure (120 bar to 240 bar) and contact time (30 min to 240 min). Fixed parameters were stirring rate (500 rpm) and 2 mL of lipid dispersion with a lipid concentration of 5 mM. A size of less than 300 nm, a PdI of less than 0.35 and a SAL of 6 log (10−6) were set as liposomes CQAs.
20 experiments of the experimental design were conducted with a formulation composed of SPC/CHOL/DSPE-PEG2000 (65/30/5) at 5 mM. To avoid as much lipid degradation as possible, the shortest possible contact time was desired. Given the interactions between pressure and temperature, and between pressure and contact time, a high pressure of 240 bar was chosen with a short contact time of 30 minutes. These conditions (80°C, 240 bar, 30 min) coincide with the conditions to produce liposomes by PGSS as described by Penoy et al [5]. This condition was then validated for the production and sterilization of liposomes in a single step and transfered to other liposome formulations.
CONCLUSION
In this study, the possibility of using ScCO2 for the production and sterilization of liposomes in a one-step process was evaluated. By applying a QbD strategy, this work allowed to determine the influence of the process parameters to obtain sterile liposomes with compatible physicochemical properties for drug delivery in a completely one-step process without the use of organic solvents and sterilization additives.