Category: Manufacturing and Bioprocessing
Purpose: Liposomal based delivery systems have demonstrated their potential as versatile platforms to deliver many different compounds including small molecules and various genetic materials. However, achieving the quality target product profile of liposomal formulations is considerably more difficult than traditional formulations and is an area of interest for the pharmaceutical industry and regulatory agencies. Therefore, it is important to identify critical quality attributes and understand how critical process parameters and key material attributes may affect the quality of liposomal products. The critical quality attributes of interest include z-average particle size, polydispersity index, and zeta-potential. In this work, process parameters of a continuous manufacturing system and the material attributes of liposomal formulations were studied for their effect on critical quality attributes using multiple design of experiments (DOE) studies.
Methods: Continuous liposomal processing technology based on the ethanol injection method consisting of an injection port with coaxial turbulent jet in co-flow was used to controllably form liposomes1. Multiple DOE studies applying a full factorial design were used to study the critical quality attributes of liposomes such as the Z-Average particle size, the polydispersity index (PDI), and the zeta-potential. In this study, either hydrogenated soy phosphatidylcholine (HSPC) or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were used as the main lipid in the formulation. The material attributes that were examined in this study include the mole percentage of cholesterol (30 to 50), salt type (sodium chloride, phosphate buffer [pH 7.4]), and phosphate buffer saline [pH 7.4] (PBS)). The mole percentage of charged lipid, 1,2-distearoyl-sn-glycero-3-phosphoglycerol (DSPG-Na), was fixed at 5 percent. The injected lipid concentration was fixed at 10 mM. The process parameters that were examined included liposomal formation temperature (20 to 60°C) and aqueous flow rate (70 to 160 mL/min). The formation temperature and flow rate were set to five levels and three levels, respectively.
Results: Aqueous flow rate and liposome formation temperature both had significant impact on the particle size distribution of the liposomes. Larger particles were formed at the slower flow rates for all three buffers. Liposomes made with PBS as the hydration medium produced larger sized liposomes while sodium chloride produced liposomes with the smallest size. As the mole percent of cholesterol in the formulation increased, the particle size also increased (Figure 1). Low PDI (≈ 0.1) was achieved for most samples but a higher PDI was observed near critical temperatures of the formulations. All developed models had a R2 ≥ 0.95.
Conclusion: The significance of this work is that it identifies key factors in continuous processing of complex dosage forms and establishes relations between process parameters and material attributes on quality attributes of liposomes such as particle size, polydispersity, and zeta potential. This work identifies key zones where monodispersed liposomes can be controllably produced. The models developed from the interactions between material attributes and process parameters illustrates key transition zones for the two liposomal formulations. Furthermore, liposomes with a higher mole percent of cholesterol appear to have a higher transition temperature which could lead to increased stability in physiological conditions. The increased mole percent of cholesterol results in increased bilayer fluidity. Lastly, this work can be used to identify a design space for liposomal formulations containing HSPC and DPPC.
Costa, Antonio P., et al. "Liposome Formation Using a Coaxial Turbulent Jet in Co-Flow." Pharmaceutical research 33.2 (2016): 404-416.
Disclaimer: This abstract reflects the views of the authors and should not be construed to represent the FDA’s views or policies.
Antonio Costa– Assistant Research Professor, University of Connecticut, Storrs Mansfield, Connecticut
Su-Lin Lee– Science Staff, USFDA, Silver Spring, Maryland
Xiaoming Xu– Senior Staff Fellow, U. S. Food and Drug Administration, Silver Spring, Maryland
Celia Cruz– Division Director, FDA/CDER/OPQ/OTR/DPQR, Silver Spring, Maryland
Diane Burgess– Distinguished Professor of Pharmaceutics, University of Connecticut, Storrs Mansfield, Connecticut