Phopholipid bilayers

FIGURE 7.31. (A) Schematic representation of the bilayer membrane formed by PEE37-b-PEO40 and for comparison a similar representation of a phopholipid bilayer. (B) Dispersion in water of PEE37-b-PEO40 showing next to vesicles, rod-like micelles (grey arrow) and spherical micelles (black arrow). Reproduced with permission of the American Association for the Advancement of Science. 

Terao, J., Piskula, M. and Yao, Q. Protective effect of epicatechin, epicatechin gallate, and quercetin on lipid peroxidation in phopholipid bilayers. Arch. Biocem. Biophys. 308, 278-284 (1994). 

Although the drug delivery to the lipid bilayer membrane is just the first step for bioactivities and phopholipid vesicles are rather simple in view of the composite structure of biomembranes, the unambiguous specification of the preferential location of the drug is essential the successive processes of the action are expected to be induced via the delivery site in membranes. We expect more advances in the dynamic NMR study, so that we can get insight into the mechanism of DD in membranes. 

Liposomes are vesicles composed of naturally occurring or synthetic phopholipids. The bilayer structure can be single- or multicompartment. The size can also vary from smaller than 1pm to larger than 10 pm. When negatively charged lipid molecules, which form liposomes, interact with divalent cations, a solid, multilayered, crystallaine structure called cochleate is formed. Because liposomes and cochleates can protect antigens from the GI tract and deliver them to the Peyer s patches, they have been exploited as an effective delivery system for oral vaccination. 

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