Dicetyl phosphate-cholesterol

Figure 6. Average area per molecule of dicetyl phosphate-cholesterol monolayers at various surface pressures...

The concept of ion-dipole interaction between lecithin and cholesterol has been suggested by many workers for the packing of these lipids in myelin or in the cell membrane (18, 19, 52). This concept is not supported by the surface potential measurements of mixed monolayers of lecithin and cholesterol. In contrast to dicetyl phosphate-cholesterol... 

Monolayers of dicetyl phosphate-cholesterol follow the additivity rule for average area per molecule, whereas lecithin—cholesterol mono-layers deviate from it. The reverse is true for the additivity rule of average potential per molecule. Thus, the surface potential indicates that there is no interaction (or complex formation) between lecithin and cholesterol, but there is ion-dipole interaction between dicetyl phosphate and cholesterol as well as between phosphatidic acid and cholesterol. 

Bromination of acetal (98) and dehydrobromination gave unsaturated acetal (99) <83AQ2io>. Hemiacetals, (e.g., (100)), have been synthesized for use as covalent carriers and for the preparation of liposomes containing dicetyl phosphate, cholesterol, and trypsin <87GEP(0)3619883>. Bis-hemiacetal (101) could be obtained by the reaction of hexafluoroacetylacetone and glycol, but this compound decomposes on standing <67NKZ470>. 

Fluorometric and spectrophotometric studies of filipin-cholesterol interaction showed that the stoichiometry of the interaction was 1 1 [150] or 1 1.5 [146,147]. UV spectrophotometry changes have been used to monitor the stoichiometry of the interaction between filipin and free or liposome-bound cholesterol. Analysis of aqueous dispersions suggested that the stoichiometry was 1 1 [171]. Lecithin, dicetyl phosphate-cholesterol liposomes only produced maximal spectral changes of filipin when the sterol polyene ratio was 1 1 [172]. Filipin released trapped ion markers from sterol—phospholipid liposomes. The rate of release was dependent upon cholesterol content of the liposome membrane (maximum at sterol phospholipid ratio of 1 1) and upon the molar fllipin sterol ratio (maximum at fllipin sterol ratio of 1 1). 

Occlusion is a condition that could affect drug transport from niosomes and through the stratum corneum. Such an effect was reported for saturated estradiol niosomal formulations composed of polyoxyethylene alkyl ether surfactants and sucrose ester surfactants with cholesterol and dicetyl phosphate, for which occlusion enhanced the drug human stratum corneum transport [43]. 

Niosomes are non-ionic surfactant vesicles. They have been used to develop a vaccine-delivery system by peroral and oral routes. Ovalbumin was encapsulated in various lyophilized niosome preparations consisting of sucrose esters, cholesterol, and dicetyl phosphate. Encapsulation of ovalbumin into niosomes consisting of 70% stearate sucrose ester and 30% pal-mitate sucrose ester (40%i mono-, 60% di/triester) resulted in a significant increase in antibody titers in serum, saliva, and intestinal washings. ... 

Negatively charged (ingredients egg lecithin-cholesterol—phosphatidic acid-dicetyl phosphate, ratio 33 4.46 10 3.24 mg)... 

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