Abstract 1331: Janus nanostructures for magnetic resonance imaging and enhanced photothermal therapy for cancer theranostics
Authors: Sansanaphongpricha Kanokwan , Chen Hongwei , Sun Kai , Wen Bo , Sun Duxin 
Published: July 2016

Abstract
Photothermal therapy (PTT) using nanoparticles has been extensively studied to eliminate cancer cells. PTT is a local therapy with less harmful systemic effect compared to other treatments such as chemotherapy. Iron oxide nanoparticles have been used as a photothermal agent to absorb and convert near infrared (NIR) light to thermal energy resulting in temperature increase. However, to produce high temperature, high-energy laser power is necessary which causes non-specifically damage to normal tissues surrounding tumor tissue. We report herein the new type of nanostructure called “Janus”, which composed of iron oxide and gold nanoparticles in asymmetrical fashion to significantly enhance the PTT effect compared to traditional iron oxide nanoparticles. The higher PTT efficiency of Janus nanostructure is resulted from the coupling effect between iron oxide and gold nanoparticles. In addition, Janus nanostructures also provide a great magnetic resonance imaging (MRI) capability and a photothermal effect, which could be used in cancer theranostics.
The Janus structure (JNS) was generated using 15 nm iron oxide (IONP) and 5 nm gold nanoparticles (AuNP) that were encapsulated in a thermo-cleavable polymer by using seed-mediated self-assembly method. JNS was determined by transmission electron microscope (TEM) and x-rays diffraction elemental mapping (XED). It clearly shows that IONPs and AuNPs rearrange in an asymmetrical structures. TheT2 relaxivity of JNS at different iron concentrations was determined. JNS yield almost 3 times higher R2 relaxation compared to Feridex, which is a commercially available iron oxide nanoparticles for MRI contrast agent. PTT efficiency of JNS was investigated in SUM 159 breast cancer cell line by irradiating the cell with 885 nm laser at 0.45 watt for 10 minutes. Interestingly, JNS generate a significantly higher temperature after 10 minutes of laser irradiation compared to IONPs alone, AuNP alone, and the mixture solution of IONP and AuNP at the same concentration of either iron or gold. We also examined the cell viability by alamar blue assay after photothermal treatment. SUM 159 cells were treated with JNS, IONP micelles alone, AuNP micelles alone, a mixture solution of IONP micelles and AuNP micelles. The cells treated with JNS have significant lower viability among other groups due to higher PTT efficiency.. We anticipate that AuNPs and IONPs could have an electron coupling effect among particles resulting in the enhanced temperature for PTT for cancer treatment. In conclusion, JNS provide a great MR imaging capability and PTT efficiency, which could be potentially applied for cancer treatment.
Citation Format: Kanokwan Sansanaphongpricha, Hongwei Chen, Kai Sun, Bo Wen, Duxin Sun. Janus nanostructures for magnetic resonance imaging and enhanced photothermal therapy for cancer theranostics. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1331.