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Article

Synthesis of Near-Infrared-Absorbing Nanoparticle-Assembled Capsules

Supporting Info

Jie Yu,^† Mohammad A. Yaseen,^‡ Bahman Anvari,^‡^§ and Michael S. Wong*^†^#

Departments of Chemical and Biomolecular Engineering, Bioengineering, and Chemistry, Rice University, Houston, Texas 77005

Chem. Mater., 2007, 19 (6), pp 1277–1284

DOI: 10.1021/cm062080x

Publication Date (Web): February 21, 2007

†

Department of Chemical and Biomolecular Engineering, Rice University.

‡

Department of Bioengineering, Rice University.

Current address: Department of Bioengineering, University of California, Riverside, CA.

Corresponding author. E-mail: mswong@rice.edu.

Department of Chemistry, Rice University.

Abstract

Indocyanine green (ICG) is an FDA-approved photosensitizer dye used in clinical settings for optical diagnostics and near-infrared laser-based therapy. However, the rapid clearance and nonspecific vascular plasma binding issues impede ICG performance. Encapsulating ICG within a colloidal matrix is a potential approach to solving these problems, but thus far, there has been limited success. A new strategy, based on the nanoparticle assembly synthesis of stable, non-liposomal nanoparticle/polymer microcapsules, to encapsulate ICG is presented. Nanoparticle-assembled capsules (NACs) are prepared at room temperature, in aqueous solution, and at neutral pH by combining a polyallylamine solution, a phosphate solution, and an aqueous sol of silica nanoparticles; ICG-containing NACs with 0.6−1.0 μm diameter are prepared by adding an ICG solution before the nanoparticle sol. ICG loading is readily controlled with an attainable maximum loading of 23 wt %. There is negligible leakage from the capsules after 24 h at room temperature in phosphate buffer saline solution, with 17% ICG leakage after 8 h at 37 °C. ICG-containing NACs are capable of heat generation in response to near-infrared laser irradiation and are stable to multiple photothermal heating cycles. Fibroblast cells exposed to these capsules remain viable after 2 days of incubation. ICG-containing NACs are a promising material for new photothermal therapy applications and are illustrative of a new approach for encapsulating organic dye compounds.