Photothermally triggerable solid lipid nanoparticles containing gold nanospheres

Abstract

Abstract Photothermally triggerable solid lipid nanoparticle (SLN) was prepared by including gold nanoparticle (GNP) in the matrix of SLN. GNP was prepared by reducing gold ions in aqueous phase. The shape of GNP was spherical on TEM photo and the mean diameter, determined by dynamic light scattering, was 54 nm. GNP was dispersed in the melt of dodecanoic acid (DA) using cetyltrimethylammonium chloride as a stabilizer. The mixture melt (around 50 °C) was put in Tween 20 solution (0.5%, 1%, 2%) of the same temperature, emulsified and cooled in an ice bath to obtain SLN containing GNP. Thermograms revealed that Tween 20 solution (0.5%) allowed for the formation of SLN without an appreciable decrease in the melting point. GNP was found in the inside of SLN on TEM photo. The temperature of the SLN suspension of which GNP concentration was 6.6 μM increased from 26 °C to 36.6 °C upon 60 min-near infrared (NIR) irradiation, possibly due to the surface plasmon resonance oscillation of GNP. Despite the temperature during the NIR irradiation was far below the melting temperature of SLN matrix (around 43 °C), the NIR irradiation-induced release degree of Nile red (a fluorescence dye) loaded in the SLN was calculated to be as high as 38%. Since GNP was in close contact with the matrix of SLN, the fatty acid matrix adjacent to GNP could be locally heated, melted and fluidized, leading to a promoted release of the payload.