(671g) Gold Nanorods for ANTI-Tumor Applications

Gold nanoparticles have attracted much attention due to their many advantageous properties. They have a size range of 1-100 nm and can be easily incorporated into biological systems. Also researchers have found that gold nanoparticles exhibit stability, low toxicity, facile fabrication and functional flexibility. They have also been investigated for their brilliant colors. Their unique optical properties result from the localized surface plasmon resonance (LSPR) effect. When a light wave front passes the gold nanoparticles, the oscillating electromagnetic field of light will cause a collective movement of the free electrons with respect to the positively charged metallic lattice, resulting in a standing oscillation of the electron density in resonance with the lightâ??s frequency. At this frequency, both the scattering and absorption of gold nanoparticles are strongly enhanced. This enhanced scattering can be used in areas like imaging and disease diagnosis, while the enhanced absorption can be applied in areas like photothermal therapy.

The LSPR band of gold nanoparticles can be tuned by changing their size, shape or structure. Researchers have been trying to tune the frequency to the near-infrared region (650-900nm, NIR region), within which the light has a maximum depth of penetration in tissues and blood. This makes the gold nanoparticles promising candidates for in vivo applications. For example, gold nanoparticles with LSPR frequency in the NIR region, if combined with antibodies or folic acid, can be used for combined imaging and photothermal therapy of cancer. Anti-tumor drugs can also be conjugated onto gold nanoparticles for photothermal-chemotherapy. These novel treatments can overcome the shortages of conventional ones in that functionalized gold nanoparticles can selectively target and kill the tumor cells while having little or no influence on the surrounding healthy cells.

Among different gold nanoparticles, gold nanorods have been of high interest due to their tunability and large red shift towards the NIR region. Using the seed-mediated growth method, the LSPR band of gold nanorods can be tuned to cover the entire NIR region by simply changing the amount of one reactant. Furthermore, gold nanorods can be readily conjugated with different molecules, like polyethylene glycol (PEG), folic acid, antibody, DNA, peptides and anti-tumor drugs, for various applications. In our study, we synthesized gold nanorods of different aspect ratios, tested their cytotoxicity and modified them with different molecules like PEG for future research. This in vitro cell study showed that bare gold nanorods can kill more than half of breast cancer cells (MDA-MB 231) at a concentration as low as 18.75 μg/ml while having a limited influence on human dermal fibroblasts up to 75 μg/ml. Therefore, there is a suitable concentration range of 18.75 â?? 75 μg/ml in which these novel gold nanorods can selectively kill the tumor cells, suggesting they should be further studied for a wide range of medical applications.