Characterization of Liposomes as Chemotherapeutic Drug Carriers

The DelsaNano series is a new generation of instruments that use photon correlation spectroscopy (PCS), which determines particle size by measuring the rate of fluctuations in laser light intensity scattered by particles as they diffuse through a fluid, for size analysis measurements and/or electrophoretic light scattering (ELS), which determines electrophoretic movement of charged particles under an applied electric field from the Doppler shift of scattered light, for zeta potential determination.

This series has a broad range of capabilities, including conventional static and automatic titration measurements for both size and zeta potential distributions of suspended particles in a wide range of size and concentration. The DelsaNano also can measure zeta potential of a solid surface or film.

Liposomes as Chemotherapeutic Agent Drug Carriers

Liposome, a small, closed vesicle composed of a lipid bilayer membrane, is attracting attention as a drug carrier for chemotherapeutic agents because of its ability to easily regulate lipid composition, particle diameter, charge, etc., and the ability to facilitate targeting by modifying antitumor peptides and antibodies on particle surface. Its particle diameter is a factor that affects pharmacokinetics.

Factors that Affect Liposome Pharmacokinetics

Liposome particles can accumulate in solid tumors as the result of enhanced permeability and retention (EPR) effect* if its size is about 100-200 nm. Because liposome pharmacokinetics is affected by the surface charge and size of liposome particles, characterization of these parameter is very important.

Measuring Particle Diameter and Zeta Potential of Liposomes

In this study, a zeta potential and particle size analyzer (DelsaNano C) was used to measure the particle diameter and zeta potential of liposomes (Sigma, Liposome Kit (L-á-phosphatidylcholine (egg yolk), 63 µmol; stearylamine, 18 µmol; and cholesterol, 9 µmol)). Samples were dispersed in physiological saline and filtered by using a filter with a 0.2-µm pore size. Then the particle diameter was measured by means of the dynamic light scattering method. The particle diameter distribution is shown in Figure 1. The average particle diameter was 114.6 nm.

Size distribution of liposome particles dispersed in physiological saline.

Figure 1. Size distribution of liposome particles dispersed in physiological saline.

Its zeta potential is shown in Figure 2. The zeta potential was +24.4 mV.

Zeta potential distribution of liposome particles dispersed in physiological saline.

Figure 2. Zeta potential distribution of liposome particles dispersed in physiological saline.

* EPR effect: New blood vessels induced by cancer have higher permeability than normal blood vessels. As a result, macromolecules of a certain particle diameter permeate through its membrane. However, lymphatic ducts are undeveloped in tumor tissues, so excretion is difficult. This phenomenon indicates the accumulation of macromolecules (liposomes) of a certain particle diameter.

This information has been sourced, reviewed and adapted from materials provided by Beckman Coulter, Inc. - Particle Characterization.

For more information on this source, please visit Beckman Coulter, Inc. - Particle Size Characterization.

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