Micelles and liposomes can serve as vehicles used to solubilize and carry bioactive compounds to their site of action, thus increasing their bioavailability. First experience has been made using vitamins and enzymes as functional food additives. Moreover, micelles could be useful to deliver drugs to a defined site of action, thus reducing frequently occurring side effects of systemic drug administration. Micelles are true nano-materials with a size range of 10 to 30 nm in diameter. Ideally, they should have a narrow size distribution. Furthermore, they have to be stable and should release their active compound only in the target region. Characterization of the micelle suspensions is vital to guarantee these properties and has to cover several aspects. One important point is size distribution, which has to be determined with high resolution. Moreover, molar mass data are important, because the combination of mass and size information allows to elucidate to which extent active compound molecules have been incorporated into the micelle.
Such difficult analytical tasks cannot be approached using conventional sizing techniques applied to an unseparated sample. Designed as an advanced system for macromolecular characterization, the Wyatt Eclipse utilizes the principle of asymmetrical Flow Field-Flow Fractionation (AF4), which physically separates the components with very high resolution. Each fraction eluting from the channel is characterized with respect to radius and molar mass. In this contribution we show how a variety of valuable information on molecular mass and size of micellar and liposomal particles can be retrieved by using a sophisticated system consisting of the Eclipse separation system combined with a Wyatt DAWN HELEOS II MALS detector.
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