Real-time monitoring of membrane composition for liposomal drug formulations in continuous manufacturing.

Purpose: Liposomes are lipid-based vesicles with the ability to entrap drugs. Their applications continue to benefit from advances in technology and manufacturing. When it comes to liposomes, or any nanomedicines, attributes such as membrane composition, size, and drug encapsulation are important to consistently deliver the intended performance of drug products. Newly adopted continuous manufacturing processes present challenges for real-time critical attribute analysis, as most characterization techniques employ a batch-based process. Here, we present a methodology to verify liposome membrane composition in a manner that can be implemented in continuous manufacturing process by detecting changes in surface tension. Methods: 8 capillary tubes (25 µl) were simultaneously submerged in 96 well plates. Wells were loaded with 250 µl of a Doxil-like liposome formulation at a concentration of 16 mg/ml. DSPEPEG ratios varied from 2.6%, 3.9%, 4.5%, 5.3%, 6%, 8%, 9%. Cholesterol molar ratio was kept at 38%, HSPC content varied dependent on DSPEPEG ratio. Three different protocols were evaluated: single 10-second submersion, 45 continuous submersions (500 milliseconds each), and 25 µl prefill followed by 15 submersions. Results: Rise measurements demonstrated significant surface tension differences between 5.3% and all other ratios using the prefill method. In addition, both single and multiple immersion protocols showed capillary rise hysteresis. Conclusions: Preliminary studies verify surface tension can be used to distinguish PEG variations in liposome membrane composition. Additional protocol and method development is required to reduce capillary rise hysteresis and further enable real-time monitoring of membrane composition in continuous manufacturing.