Preparation and photothermal induced release from cubic phase containing gold nanoparticle

Cubic phase containing gold nanoparticles (GNP) were prepared by hydrating the mixture of molten monoolein (MO)/cetyltrimethylammonium bromide (CTAB)/GNP. GNP was prepared by reducing gold ions in an aqueous phase. On the TEM photo, the shape was almost spherical, and the size was in 10 nm–20 nm. GNP was included in the MO cubic phase so that the molar concentration was 1.5 mM and CTAB was included in the cubic phase so that CTAB/GNP molar ratio was 0.089/1 to 13.7/1. Without CTAB, GNP was hardly dispersed and existed as lumps in the cubic phase but the dispersity increased when the CTAB/GNP molar ratio increased. According to the TEM photos, GNP stabilized with CTAB could be embedded in the matrix of MO cubic phase without affecting the integrity. According to the polarizing microphotography and the calorimetric study, GNP and CTAB had little effect on the phase transition temperature of cubic phase. The release degree in 60 min of FITC-dextran from cubic phase containing CTAB/GNP (13.7 mM/1 mM) under near-infrared irradiation was about three times higher than the release degree under no irradiation. The photothermal energy might induce the local phase transition of the cubic phase, leading to a promoted release.