Wyatt Technology Europe’s Eclipse Achieves Accurate and Reliable Characterisation of Micelles

Wyatt Technology Europe, the world leader in absolute macromolecular characterisation instruments and software, announces that its innovative Eclipse asymmetrical Flow Field-Flow Fractionation (AF4) system achieves successful characterisation of micelles suspensions.

Narrow size distribution is vital to guarantee that micelles are stable and can release the active compound only at the final target. The Eclipse is ideally suited to analyse the size distribution with high resolution and the findings of this analysis are detailed in a new, free-of-charge application note which is available to download from the article webpage.

In addition to size, the molar mass should be measured to reveal its loading efficiency for example, how many molecules of the active compound are incorporated in the micelle. Furthermore, the analysis shows whether the micelle composition is homogeneos as a function of size. This method has shown in some cases that micelles with a different ratio of detergent and payload molecules can exist.

Difficult analytical tasks like these cannot be solved using conventional sizing techniques such as Particle Sizers working on the basis of Photon Correlation Spectroscope (PCS), because the resolution of the method is too limited and only hydrodynamic size can be extracted. Size Exclusion Chromatography (SEC) is too limited in resolution in larger sizes and specific interactions with the column matrix could occur as well as sample degradation due to high shear forces. Wyatt Technology Europe’s Eclipse works on a universal basis for all micelle samples and offers valid, unambiguous results compared to other traditional techniques.

Working on the principle of AF4, Wyatt’s Eclipse overcomes the limitations of conventional column chromatography being able to physically and rapidly separate the particulates with ultra-high resolution. Displaying high selectivity, it is able to separate both soluble and colloidal components over a wide size range from a few nanometers to a few micrometers. Each fraction eluting from the channel is characterized according to radius and molar mass. The Eclipse requires only minimal sample preparation and shearing forces are completely absent.

For this particular application, the Eclipse was used in conjunction with Wyatt’s DAWN HELEOS MALS (Multi-Angle Light Scattering) and Optilab rEX instruments to calculate the concentration, molar mass and radius of the eluting fractions. One example compares the size distribution of different preparations of a micelle with increasing amount of drug loading. The analysis shows a bimodal micelle structure for one sample versus a broader, but unimodal micelle peak for the second preparation. This data is useful to monitor and optimize the preparation procedures for loaded micelles.