If you hold your hand toward the Sun, you will find your fingers are glowing red owing to the preferential penetration of red and near infrared (NIR) light. The totally benign tissue-penetrating NIR light can be absorbed by tumor-homing antennas and converted into heat to kill cancer cells. This new treatment option is called photothermal tumor therapy (PTT). PTT is widely regarded as a promising alternative to chemotherapy that has long been plagued by problems such as the toxic side-effects of the chemotherapy agents and the difficulty to selectively deliver them to the tumor sites. Many antennas including organic dyes, polymers, and inorganic nanoparticles (1 nanometer is one millionth of...

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If you hold your hand toward the Sun, you will find your fingers are glowing red owing to the preferential penetration of red and near infrared (NIR) light. The totally benign tissue-penetrating NIR light can be absorbed by tumor-homing antennas and converted into heat to kill cancer cells. This new treatment option is called photothermal tumor therapy (PTT). PTT is widely regarded as a promising alternative to chemotherapy that has long been plagued by problems such as the toxic side-effects of the chemotherapy agents and the difficulty to selectively deliver them to the tumor sites. Many antennas including organic dyes, polymers, and inorganic nanoparticles (1 nanometer is one millionth of the width of a human hair) have been developed, among which gold nanorods (AuNRs) are considered as one of the most promising candidates. Clinical translations of AuNRs have not been realized yet because the NIR light absorbed by AuNRs has a rather short wavelength range within ~650-850 nanometers. The penetration depth of NIR light in human tissues is limited by the two NIR-transparent windows and increases with increasing wavelength. For ~650-850 nanometers, this depth was found to range from ~0.2-4 mm, which may be acceptable for subdermal carcinomas but falls short to reach deep-seated tumors. In this study, we propose to develop colloidal molecules consisting of AuNRs linked together via biodegradable polymer ligands. We expect to obtain red-shifted NIR absorption due to the quantum confinement effect to treat deep-seated tumors. Our design has the added benefits in that the field couplings among AuNRs will be reinforced to achieve higher photothermal conversion efficiency, and the colloidal molecules will be disassembled and deactivated by enzymatic degradation to minimize potential long-term adverse effects once the PTT is done. If successful, this study will break the upmost limitation of AuNRs and open a new path to develop AuNRs formulations for clinically viable PTT.

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