Photothermally induced release from liposome suspended in mixture solution of gold nanoparticle and thermo-sensitive polymer

Abstract

The release profiles of calcein from dipalmitoylphosphatidylcholine (DPPC) liposome, with/without gold nanoparticle (GNP) and poly(N-isopropylacrylamide-co-butylmethacrylate) (PNIPAM-BMA), were observed as function of temperature and NIR irradiation. DPPC liposome without GNP/copolymer released calcein substantially only when the temperature was higher than the phase transition temperature (PTT, 41 °C) of the liposome membrane. Meanwhile, the liposome with GNP and PNIAPM-BMA released its payload even below PPT (e.g. even at 37 °C). The thermal contraction of the thermo-responsive polymer would be responsible for the release occurred below PPT. On the other hand, under NIR irradiation, DPPC liposome with GNP and PNIPAM-BMA showed a stepwise release. The first step of release is possibly due to the thermal contraction of the polymer and the second step of release is possibly because of the phase transition of the liposome membrane. The photothermal energy generated by GNP could be responsible for the NIR irradiation-triggered release.