Wyatt Technology FFF-MALS particle measurement system

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Wyatt Technology’s field flow fractionation (FFF) technology combined with multi-angle light scattering (MALS) and quasi-elastic light scattering (QELS) enables rapid measurements of particle size, size distribution and particle count, as well as structure. The combined system performs difficult sizing tasks in key areas of research and development in molecular biology and nanotechnology analyses, including the separation and characterisation of liposomes and nanoparticles.

Liposomes are made of lipid bilayers. The size of a liposome ranges from 20 nm up to several micrometres and may be composed of one or several concentric membranes. Liposomes possess unique properties owing to the amphiphilic character of the lipids, which makes them suitable for drug delivery. Liposomes have attracted attention as potential vehicles for drug delivery to selected cells or tissues in vivo. Therefore, it is of great importance to monitor liposome size and encapsulation during liposome research, formulation, manufacturing and quality control. However, conventional methods to characterise liposomes fail to perform efficiently and to cover the whole size of liposomes.

A method combining the Wyatt Technology Eclipse FFF system with a DAWN HELEOS and online QELS has been used to analyse two liposome samples, one empty and one filled. The results demonstrated that the combined method is capable of determining the degrees of encapsulation and the internal structures of the two liposomes without making assumptions.

The FFF system offers a number of advantages over column separation techniques for many applications. The method is robust and easy to use, involving minimal shearing and enabling a broad separation range, from small proteins (nanometres) to large particles (micrometres). FFF is a non-destructive technique that achieves true particle size distribution and online absolute characterisation of a range of solutions and dispersions. Combined with MALS detectors, the method can determine the absolute size and molar mass distributions as well as the structure and conformation of the particles.