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Nanoparticle-mediated photothermal therapy: A comparative study of heating for different particle types

Authors

  • Varun P. Pattani MS,

    1. Department of Biomedical Engineering, The University of Texas at Austin, 107 W Dean Keeton, C0800 Austin, Texas 78712
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  • James W. Tunnell PhD

    Corresponding author
    1. Department of Biomedical Engineering, The University of Texas at Austin, 107 W Dean Keeton, C0800 Austin, Texas 78712
    • Department of Biomedical Engineering, The University of Texas at Austin, 107 W Dean Keeton, C0800 Austin, Texas 78712.
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  • Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Abstract

Introduction

Near-infrared (NIR) absorbing plasmonic nanoparticles enhance photothermal therapy of tumors. In this procedure, systemically delivered gold nanoparticles preferentially accumulate at the tumor site and when irradiated using laser light, produce localized heat sufficient to damage tumor cells. Gold nanoshells and nanorods have been widely studied for this purpose, and while both exhibit strong NIR absorption, their overall absorption and scattering properties differ widely due to their geometry. In this paper, we compared the photothermal response of both nanoparticle types including the heat generation and photothermal efficiency.

Methods

Tissue simulating phantoms, with varying concentrations of gold nanoparticles, were irradiated with a near-infrared diode laser while concurrently monitoring the surface temperature with an infrared camera. We calculated nanoshell and nanorod optical properties using the Mie solution and the discrete dipole approximation, respectively. In addition, we measured the heat generation of nanoshells and nanorods at the same optical density to determine the photothermal transduction efficiency for both nanoparticle types.

Results

We found that the gold nanoshells produced more heat than gold nanorods at equivalent number densities (# of nanoparticles/ml), whereas the nanorods generated more heat than nanoshells at equivalent extinction values at the irradiance wavelength. To reach an equivalent heat generation, we found that it was necessary to have ∼36× more nanorods than nanoshells. However, the gold nanorods were found to have two times the photothermal transduction efficiency than the gold nanoshells.

Conclusion

For the nanoparticles tested, the nanoshells generated more heat, per nanoparticle, than nanorods, primarily due to their overall larger geometric cross-section. Conversely, we found that the gold nanorods had a higher photothermal efficiency than the gold nanoshells. In conclusion, the ideal choice of plasmonic nanoparticle requires not only per particle efficiency, but also the in vivo particle targeting ability under study. Lasers Surg. Med. 44: 675–684, 2012. © 2012 Wiley Periodicals, Inc.

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