Cancer Cell Imaging and Photothermal Therapy in the Near-Infrared Region by Using Gold Nanorods

Abstract

Due to strong electric fields at the surface, the absorption and scattering of electromagnetic radiation by noble metal nanoparticles are strongly enhanced. These unique properties provide the potential of designing novel optically active reagents for simultaneous molecular imaging and photothermal cancer therapy. It is desirable to use agents that are active in the near-infrared (NIR) region of the radiation spectrum to minimize the light extinction by intrinsic chromophores in native tissue. Gold nanorods with suitable aspect ratios (length divided by width) can absorb and scatter strongly in the NIR region (650-900 nm). In the present work, we provide an in vitro demonstration of gold nanorods as novel contrast agents for both molecular imaging and photothermal cancer therapy. Nanorods are synthesized and conjugated to anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies and incubated in cell cultures with a nonmalignant epithelial cell line (HaCat) and two malignant oral epithelial cell lines (HOC 313 clone 8 and HSC 3). The anti-EGFR antibody-conjugated nanorods bind specifically to the surface of the malignant-type cells with a much higher affinity due to the overexpressed EGFR on the cytoplasmic membrane of the malignant cells. As a result of the strongly scattered red light from gold nanorods in dark field, observed using a laboratory microscope, the malignant cells are clearly visualized and diagnosed from the nonmalignant cells. It is found that, after exposure to continuous red laser at 800 nm, malignant cells require about half the laser energy to be photothermally destroyed than the nonmalignant cells. Thus, both efficient cancer cell diagnostics and selective photothermal therapy are realized at the same time.

Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

“…26,27 More recently, Huang et al provided an in vitro demonstration of gold nanorods conjugated to anti-EGFR antibodies as novel contrast agents for both NIR cell imaging and photothermal cancer therapy. 28 The effectiveness of nanoparticles as biomedical imaging contrast and therapeutic agents depends on their optical properties. For instance, a high-scattering cross-section is essential for cell imaging applications based on light-scattering microscopy.…”

Optical Properties of Star-Shaped Gold Nanoparticles

“…13 The formation of more complex metal nanostructures, such as metallodielectric gold nanoshells 14 and gold nanocages, 15 shifts the LSPR resonance to the near-infrared (NIR) enabling significant diagnostic and therapeutic biomedical applications. 16,17 Here we describe the synthesis and optical properties of branched star-shaped gold nanoparticles which incorporate polarization-dependent scattering with multiple spectral peaks and strong dielectric sensitivity into a single structure.Due to the symmetric face-centered cubic lattice of gold nanoparticles, the formation of anisotropic structures requires a selective capping agent during growth. For example, roomtemperature synthesis of gold nanorods with 97% yield has recently been demonstrated by seed-mediated growth directed by the surfactant cetyltrimethylammonium bromide (CTAB), 18,19 and the process can be scaled up to 100 mL batches.…”

Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing

“…Using nanoshells with a 110 nm silica core diameter and a 10 nm Au shell, the authors reported significant reduction of human breast carcinoma epithelial cells (SK-Br-3) both in vitro and in a mouse model. Since then there have been many accounts of laser initiated hyperthermia using a variety of nanoparticles with solid Au spheres, cubes, stars, shells and rods all demonstrating successful results in photothermal applications [119,167,189,197,[206][207][208][209][210][211][212].…”