Delivered by Publishing Technology to: Rice University, Fondren Library IP: 128.42.202.150 On: Mon, 09 Jun 2014 14:55:08 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2012 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Biomedical Nanotechnology Vol. 8, 883–890, 2012 Local Field Enhanced Au/CuS Nanocomposites as Efficient Photothermal Transducer Agents for Cancer Treatment Santana Bala Lakshmanan, Xiaoju Zou, Marius Hossu, Lun Ma, Chang Yang, and Wei Chen ∗ Department of Physics, The University of Texas at Arlington, Arlington, TX 76019-0059, USA Photothermal therapy (PTT) for cancer treatment is the use of heat between 41  C and 45  C to damage cancer cells. As a new type of transducer agent for PPT of cancer, CuS nanoparticles have several advantages over gold nanostructures. The most favorable features are the low cost, simple and easy preparation, and small size for targeting. However, the CuS nanoparticle PTT efficacy needs to be improved for practical applications. In this study, the CuS nano-PTT efficiency was enhanced via the local field enhancement from Au nanoparticle surface plasmon coupling. The results show that absorbance of CuS nanoparticles in Au/CuS nanocomposites is enhanced about 2.2 times by Au nanoparticle surface plasmon coupling. Consequently, the PTT efficacy is enhanced and a power of 0.2 W/cm 2 with a 980 nm laser was sufficient for Au/CuS nano-PTT activation. We have demonstrated for the first time that surface plasmon coupling can be used to enhance CuS nanoparticle PTT for cancer treatment. Keywords: Photothermal Therapy, CuS Nanoparticles, Au/CuS Nanocomposites, Surface Plasmon, Local Field Enhancement, Cancer Treatment. 1. INTRODUCTION Cancer nanotechnology for the developing and application of nanomaterials for cancer detection, imaging, diagnosis and treatment as well as prevention is one of the most topical areas that attract a lot of attentions. 1–10 Photother- mal therapy (PTT) for cancer treatment is the use of heat between 41  C and 45  C to damage cancer cells. 11 The beauty of PTT is its dual mechanism for targeting—that is the targeting of the agents and of the light that is used locally for activation. 11 This targeting strategy can effec- tively reduce the side effects and the risk of damage to the surrounding healthy tissue. 6 12 Gold nanostructures such as nanoparticles, 13 14 nanoshells, 15 nanocages, 16 and hollow nanospheres, 17 nanoplexes, 18 as well as carbon nanotubes 19 have been investigated extensively for PTT therapy in can- cer treatment. CuS nanoparticles have a broad absorption from 700 to 1100 nm, and we first demonstrated that the interaction of CuS nanoparticles with near infrared light can generate heat that can be harnessed for PTT of cancer cells. 20 21 As a new type of agent for photother- mal treatment of cancer, CuS nanoparticles have several advantages over Au nanostructures. 20 The most favorable ∗ Author to whom correspondence should be addressed. features are the low cost, simple and easy preparation, and small size for targeting. Since our first publication on CuS nanoparticle-based PTT, 20 CuX (X = S, Se, and Te) nanoparticle based-PTT has become a hot topic. 21–24 However, the PTT efficiency using CuS nanoparticles as transducers is lower than using Au nanostructures and needs to be improved for practical applications. Here, we investigate the enhancement of CuS nanoparticle-PTT efficacy by Au nanoparticle surface plasmon coupling in Au/CuS nanocomposites for cancer treatment. A surface plasmon is a localized electromagnetic field at the metal- dielectric interface. 25 Surface plasmons can lead to sig- nificant electric field enhancement near the surface and thus increase the rate of any processes that depend on the field intensity. The field enhancement due to surface plasmon resonance is predicted to be ∼1,000 times larger than the incident field and, therefore, it can be used to increase any light excitation or transition processes at the interfaces. 26 27 Surface plasmon resonances in metallic nanoparticles are currently being exploited for a variety of applications including molecular sensing, 28 luminescence enhancement, 27 Raman effect enhancement, 29 and near- field optical microscopy. 30 Because of the localized field amplification that occurs, excitation of surface plasmons in metal nanoparticles placed on a semiconductor might J. Biomed. Nanotechnol. 2012, Vol. 8, No. 6 1550-7033/2012/8/883/008 doi:10.1166/jbn.2012.1486 883