Preparation of dimethylaminopropyl octadecanamide/stearic acid vesicles incorporating azobenzene and their UV-responsive release property

초록

UV-responsive vesicle was prepared by incorporating azobenzene in the vesicular membrane composed of dimethylaminopropyl octadecanamide (DMAPODA) and stearic acid (SA). Azobenzene intercalated in the vesicular membrane underwent cis-to-trans isomerization under the UV irradiation, confirmed by UV spectroscopy. The phase transition temperature of vesicle was found to be around 51.2 degrees C by differential scanning calorimetry. Using a negative staining technique, the vesicles were found as circular and irregular-shaped particles on the TEM photo. The mean hydrodynamic diameter of vesicles increased from 199.4 to 1597.3 nm when the lipid/azobenzene ratio increased from 100/0 to 100/5. The zeta potential of DMAPODA/SA vesicle decreased from about + 60 mV to - 60 mV when the pH value of medium increased from 3.0 to 10.0, and the inclusion of azobenzene in the vesicular membrane had little effect on the zeta potential. UV irradiation markedly promoted the release of carboxylic fluorescein loaded in vesicle incorporating azobenzene, possibly because the cis-to-trans photoisomerization would disturb the well-ordered crystalline structure of the vesicular membrane.

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