Izon’s qNano is a powerful non-optical method being used by drug delivery researchers to quantify important physical properties (size, surface charge and concentration) of liposomes and synthesized nanoparticles with unsurpassed accuracy.
Accurate characterization of the physical properties of liposome is important in fields like drug delivery as developing effective drugs requires the creation of homogenous liposome particle samples, of known concentration, that are stable and retain their drug payload.
The ability to detect modifications on the surface of the liposome is also key in applications such as targeted drug delivery, whereby changes of the liposomal surface can direct attachment and accumulation at disease specific sites within the body.
qNano is a useful tool for:
Measuring Liposome Polydispersity & Aggregation
Concentration Determination of Liposome Samples
Measuring Liposome Surface Modification
Liposome Measurement on the qNano
A series of liposome formulations were measured and characterized using the qNano instrument from Izon. Information regarding particle-by-particle size distribution, particle concentration and surface charge was obtained. The samples were dispersed in PBS buffer for measurement. In this experiment, all the samples were measured when a positive applied voltage was applied, which indicates a negative surface charge.
Example 1: Measurement of Polydispersity & Aggregation
The example below shows measurement of a liposomal preparation before and after freezing. The ability to accurately measure sample polydispersity and aggregation effects is a key feature of the qNano system. The same measurement principles can be applied to ensure homogenous and stable sizes of liposome particles during development processes of drug delivery systems.
Figure 1. Freezing of the Liposome sample has resulted in aggregation observed through increased liposome size distribution (polydispersity), as well as a decrease in overall particle numbers in the concentration results. (See Example 2, below)
Figure 2. Translocation Duration vs Particle Diameter plot shows that freezing results in an increase in sample size distribution and a decrease in electrophoretic mobility (increased translocation duration).
Example 2: Concentration Determination
A table showing particle concentration and size of different liposome samples is given below. The d90/d10 metric, illustrated below, is a measure of the size dispersity of the sample. The nearer the value is to 1 the more monodisperse the size. Freezing of the liposome preparation results in increased aggregation which increases polydispersity (d90/d10 increases from 1.3 to 2.6).
|
Sample |
Particle concentration |
Size d90/d10 |
|
Liposome |
3.5 x 1013 particles/mL |
1.3 |
|
Liposome (frozen) |
2.9 x 1013 particles/mL |
2.6 |
Example 3: Measurement of Liposomal Surface Modification
The ability to detect modifications on the surface of the liposome is also key in applications such as targeted drug delivery, whereby changes of the liposomal surface can direct attachment and accumulation at the sites of specific diseases. The example below shows accurate measurement of a liposome preparation before and after modification with PEG.
This is detectable as an increase in particle diameter (Figure 3), and electrophoretic mobility (Figures 4 & 5). The latter indicates a reduction in the surface charge of liposome particles upon PEG binding (through lower electrophoretic mobility under the same experimental conditions).
Figure 3. Addition of PEG to the liposome surface is detected as a shift in the size distribution curve.
Figure 4. Scatter plot of translocation duration (time of flight) versus particle diameter shows an increase upon PEGlyation of liposome sample for these parameters.
Figure 5. Increase in Blockade Baseline Duration (time of flight) of PEGylated Liposomes compared to original sample. This indicates a reduction in the surface charge of liposome particles upon PEG binding (which results in lower electrophoretic mobility under the same experimental conditions).
For more information please contact us at info@izon.com
