Creative Biostructure has developed and commercialized a wide range of high-quality products and innovative services that based on Mempro™ Liposome platform. Mempro™ Liposome Analysis is an important kind of our featured liposome services.
Figure 1. Schematic diagram of loading of [Cu-64]2+ into liposomes. [Cu-64]2+ traps inside the liposome and forms a complex with the encapsulated chelator (DOTA), enhancing the permeability (a); Loading efficiency of liposomes plotted as a function of time by using radio-TLC (b). (A. E. Hansen, et al., 2016)
Liposome membranes are semi-permeable. For some molecules and ions, liposomes allow them to cross the lipid bilayer, while offer a substantial barrier to others. Liposome permeability analysis is a measurement of the diffusion rate of a solute through the lipid bilayer.
Liposome membrane will reach to its highest permeability at phase transition temperature, and the permeability is lower in the gel than in fluid phase. The phase transition temperature of the bilayer is determined by the composition of the liposome. At the phase transition temperature, the permeability of the liposome to molecules such as protons and water increases.
Factors affect the relative permeability of liposome：
The major factor that determine the membrane permeability is polarity. On one hand, non-polar molecules prefer to partition into the membrane interior, permeating faster and easier; on the other hand, polar molecules are diffcult to permeate the membrane. The general sequence of hydrophilic solute permeability is as follows: large poly-electrolytes < cations < small non-electrolytes < water.
2. Fatty acid distribution:
The fatty acid distribution of lipid fraction has effect on the liposome permeability since the saturation degree of fatty acid greatly affect the phase transition temperature. Therefore, using phospholipids with longer chain fatty acids is a helpful way to increase the thickness of the liposomal bilayer and decrease the diffusion rates of all solutes through the membrane, resulting in low permeability of liposome.
3. Intermolecular interactions:
Interaction between the liposomal bilayer and introduced compounds affect membrane permeability as well. Lipids molecules such as cholesterols and sterols may induce the lipid raft formation which stabilize the lipid bilayer, leading to a reduced liposome permeability.
4. Molecular size;
5. Molecule in question;
6. The surrounding conditions;
7. The composition of the liposome.
Methods to determine the fusion and permeability of liposome：
1. Fluorescence Quenching Assays
2. Fluorescence Enhancement Assays
3. Self-Quenching Assays
4. Lipid Mixing Assays
5. Liposome electrokinetic chromatography (LEKC)
Besides permeability analysis, a wide variety of Mempro™ Liposome Analysis services based on our leading Mempro™ Liposome Technology are also available in the related sections. Please feel free to contact us for a detailed quote.
A. E. Hansen, et al. (2015). Positron Emission Tomography Based Elucidation of the Enhanced Permeability and Retention Effect in Dogs with Cancer Using Copper-64 Liposomes. ACS Nano, 9(7): 6985-6995.
M. Yoshimoto, et al. (2013). Liposome clusters with shear stress-induced membrane permeability. Chemistry and Physics of Lipids., 174: 8–16.
Y. Koda, et al. (2008). In vitro stability and permeability studies of liposomal delivery systems for a novel lipophilic endomorphin 1 analogue. International Journal of Pharmaceutics, 356: 37-43.