Measuring lipid nanoparticle cargo loading with partial specific volume distributions
Challenge
Determining the drug amount in a lipid nanoparticle
(LNP) poses a challenge, as the size and shape of the LNP may not necessarily indicate the
actual drug content within.
Traditional techniques often falter in
distinguishing between empty, partially loaded, or fully loaded LNPs, making accurate
measurement problematic.
Solution
This technique offers precise bulk separation by
identifying key properties like sedimentation and diffusion coefficients and solute
concentrations.
For effective LNP loadings determination, both particle
density discrimination and partial specific volume (PSV) are critical.
Density matching experiments, especially with D2O
density matching, have been introduced. Different LNP loadings produce unique density
profiles, facilitating differentiation.
Buffer density is fine-tuned using various D2O to H2O
ratios.
Changes in sedimentation coefficients are tracked based
on buoyancy.
SVEs under differing D2O:H2O buffer ratios are evaluated
using UltraScan2, resulting in a g(s) distribution.
Normalized G(s) distributions are derived from these
g(s) distributions, leading to the creation of a PSV distribution by extrapolating to S=0.
Experiments like sedimentation as a
function of buoyancy g(s) are used to monitor changes in sedimentation coefficients.
Conclusion
Using variable buffer densities, specific PSV
distributions can be obtained, which are pivotal in determining the loaded cargo in a
mixture of liposomes.
These PSV distributions are instrumental in deducing
properties like molar mass, density, anisotropy, and hydrodynamic radius distributions for
mixtures.
For even greater precision in measurements,
lowering the rotor speed can enhance the diffusion signal, ensuring meticulous and accurate
analysis of LNPs and their drug content.
