Preparation of ZnPC-loaded plasmonic liposome for synergistic effect of photodynamic and photothermal therapy in vitro

Abstract

Phototherapy is a promising strategy for cancer treatment due to its selective and localized therapeutic effect by laser irradiation. There are two major types of phototherapy: photothermal therapy and photodynamic therapy. Photothermal therapy damages malignant cells by using heat converted from light by an agent. On the other hand, photodynamic therapy uses photosensitizer that becomes cytotoxic upon irradiation with laser light at excitation wavelength. For photothermal therapy, biocompatible gold nanoparticles are widely studied as potential agents, as these nanoparticles show high absorption of light and efficient generation of heat by conversion from light energy. Structure of gold nanoparticles is the main factor in changing absorption wavelength, thus synthesizing gold nanoparticles with high absorption in near infrared region (NIR) is important, where the light is known to travel biological tissue deeply. For photodynamic therapy, Zinc Phthalocyanine (ZnPC) is widely used in researches as a photosensitizer, as it is highly active at NIR. However, due to its hydrophobicity, ZnPC must be delivered into cells or tissues by nanocarriers having a hydrophobic region. Among such nanocarriers, liposomes are widely used in clinics. For synergistic phototherapy by combining photothermal and photodynamic therapy, we herein introduce photosensitizerloaded gold-coated liposomes named "plasmonic liposomes". We optimized the synthesis conditions for efficient absorption of light in the NIR region. The plasmonic liposome showed optical tunability, similar to that of the conventional gold nanoshell, by controlling the thickness of gold coating. With this optical tunability and drug loading property of plasmonic liposome, we loaded NIR photosensitizer (ZnPC) in the nanoparticle, and controlled the absorption wavelength peak of plasmonic liposome to the excitation wavelength of photosensitizer. Photothermal effect of gold nanostructure and photodynamic effect of loaded ...