Summary
Liposomes are spherical lipid vesicles widely used as drug delivery platforms for both small molecules and biologics. Liposomal formulations are effective for targeted delivery and are increasingly important in pharmaceutical development, with several FDA-approved products on the market.
This application note demonstrates SAXS structural characterization of a liposome-based drug product containing API nanocrystals.
Background
The application of liposomes for targeted drug delivery has had a major impact in many biomedical areas. Liposomes are attractive as a delivery system due to their flexibility in their physicochemical and biophysical properties. The physical characterization of drug-loaded liposomes is important and required by regulatory entities to obtain marketing authorization for a drug product.
Methods & Experimental Design
Sample Information
Formulation: Liposomal drug product with nanocrystalline API
Drug form: API nanocrystals loaded within liposome carrier
Analysis method: Differential SAXS pattern (liposomes vs. blank)
Modeling: Core-shell model with refinement to experimental data
Temperature: Room temperature
SAXS Measurement
Instrument Parameters
- X-ray sourceCu Kα
- InstrumentLaboratory SAXS at DANNALAB
- Q range0.05-4.3 nm⁻¹
Results
At DANNALAB, with the use of Small Angle X-Ray Scattering (SAXS), we are capable of reconstructing the structure of a liposome carrier, either alone or loaded with a drug.
Figure 1. Measured differential SAXS pattern of a liposomal drug formulation containing an API nanocrystal.
Figure 2. Physical model used for the characterization of a liposomal drug formulation. Parameters of the model are refined to achieve the best fit between the measured differential SAXS pattern and the pattern calculated from the model.
From the core-shell model, information can be obtained about the thickness and density of the lipid bi-layers, the PEG corona, and the dimensions of the loaded nanocrystalline drug.
Conclusion
The application of liposomes for targeted drug delivery has had a major impact in many biomedical areas. Liposomes are attractive as a delivery system due to their flexibility in their physicochemical and biophysical properties. The physical characterization of drug-loaded liposomes is important and required by regulatory entities to obtain marketing authorization for a drug product.