Together with our leading Mempro™ Liposome platform and rich experience for numerous successful cases, Creative Biostructure guarantees our worldwide clients the best products and unparalleled services for liposome research & development. Size and size distribution analysis of liposomes are crucial parameters for those liposomes are designed for therapeutic use, especially by inhalation or parenteral route.
Figure 1. Schematic representations are on the left while the experimental data is on the right, correspondingly. Transmission electron micrographs (TEM) of FMIO nanoparticles (a); Size distribution of FMIO nanoparticles with an average size equal to 6.65 nm (b); Field-emission gun scanning electron microscopy of the aqueous colloidal system of FMIO nanoparticles (c); DLS measurement of FMIO colloidal dispersion (d); AFM image of ferri-liposome (e); Liposome size determined by DLS with an average size equal to 92.3 nm (f) (G. Mikhaylov, et al., 2011)
The size distribution of liposome is one of the most important properties to determine its behaviour and characteristic. There are an incresing number of methods that can be adopted to measure the size and size distribution of liposome, each with different advantages and disadvantages.
Dynamic light scattering (DLS)
DLS is also as known as photon correlation spectroscopy. This technique is based on the principle of time-depended intensity fluctuations in scattered laser light, as a result of Brownian motion of particles in suspension. DLS method is relatively easy and fast, whereas it does not have access to obtain particle shape information.
Field-flow fractionation (FFF)
FFF utilizes a channel wall that composed of a semi-permeable membrane filter that chosen with a suitable MWCO to determine the size distribution of liposome. Small liposomes elute earlier than large liposomes since they have higher diffusion coefficients in FFF, while small liposomes elute last in HPLC-SEC. Size distribution measurements by flow FFF have a lot of advantages such as convenient, rapid, non invasive, no need for prior calibration, and broad seperation range. The major drawback of this method is the highly cost.
Electron microscopy (EM)
Electron microscopy is widely used in size anylysis of liposomes, providing valuable information. By using molybate or phosphotungstate as the stain, negative staining electron mrcroscopy enable accurate determination of liposome size, and give useful images of individual vesicles to measure the number of lipid bilayers. Freeze fracture electron microscopy is used as a powerful tool in order to observe morphological structure of the liposome. The major disadvantages of EM based techniques include time consuming and expensive.
HPLC-SEC (Size-exclusion chromatography) deliver a better liposome separation effect than conventional SEC. HPLC-SEC are useful in quantification of liposome populations according to a time-depended resolution of hydrodynamic size.
Besides size and size distribution analysis, a variety of liposome analysis services shown in related sections are also available. Creative Biostructure is more than happy to share our advanced Mempro™ Liposome Technology to facilitate your liposome research. Please feel free to contact us for a detailed quote.
R. Garcia-Diez, et al. (2016). Size Determination of a Liposomal Drug by Small-Angle X-ray Scattering Using Continuous Contrast Variation. Langmuir, 32: 772-778.
D. Mastrogiacomo, et al. (2015). Lipid/detergent mixed micelles as a tool for transferring antioxidant power from hydrophobic natural extracts into bio-deliverable liposome carriers: the case of lycopene rich oleoresins. RSC Advances, 5: 3081–3093.
G. Mikhaylov, et al. (2011). Ferri-liposomes as an MRI-visible drug-delivery system for targeting tumours and their microenvironment. Nature Nanotechnology, 6(9): 592-604.