Spray‐dried microparticles composed of cinnamoyl poly(N‐isopropylacrylamide‐co‐hydroxyethylacrylate) and gold nanoparticle

Abstract

ABSTRACTTemperature‐ and NIR irradiation‐responsive microparticles composed of cinnamoyl poly(N‐isopropylacrylamide‐co‐hydroxyethylacrylate) [CinP(NIPAM‐HEA)] and gold nanoparticle (GNP) were prepared by a spray‐drying method. According to the cloud points determined by an optical method, the HEA content in P(NIPAM‐HEA) had no marked effect on the lower critical solution temperature (LCST). However, the cinnamoyl group content in CinP(NIPAM‐HEA) had a significant effect on the LCST. The LCSTs determined by a calorimetric method was in agreement with those determined by an optical method. The hydrodynamic mean diameter of gold nanoparticle (GNP) prepared by reducing gold ions was about 30 nm and it seemed to be a nanosphere on TEM photo. Spray‐dried CinP(NIPAM‐HEA) microparticles containing GNP was 1.5 μm to 12 μm in diameter on SEM photo. Gold was detected on the energy‐dispersive X‐ray spectrum of the microparticles. The amount of FITC‐dextran released for 12 h from the microparticles was much higher at temperatures above the LCST (at 37 °C and 45 °C) than below the LCST (at 20 °C and 25 °C). The cumulative release amount in 12 h was only about 3% without NIR irradiation, whereas the value was about 26.5% when NIR was irradiated to the microparticle suspension. The photothermal energy generated by GNP was believed to render the thermosensitive copolymers de‐swollen and hydrophobic, allowing for the active release of dye from the microparticles. The NIR irradiation‐responsive GNP‐loaded microparticles could be applied to the development of NIR‐responsive drug carriers which release their contents in response to an external stimulus (i.e., NIR irradiation). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44141.