Direct Synthesis of Water-Soluble Aptamer-Ag2S Quantum Dots at Ambient Temperature for Specific Imaging and Photothermal Therapy of Cancer

Water-soluble Ag2S near-infrared (NIR) fluorescent quantum dots (QDs) are directly synthesized at ambient temperature for specific cancer imaging and photothermal therapy (PTT) using a designed aptamer (Apt43) as template, which consists of the following two fragments: an aptamer S2.2 sequence for specifically recognizing the cancer cells and an 18-cytosine (18-C) extending spacer for growing Ag2S QDs. The synthesized Ag2S QDs (Apt43-Ag2S QDs), which exhibit strong absorption and fluorescence emission in the NIR region and high photothermal conversion capabilities, can specifically recognize MCF-7 cells (human breast cancer cells) and are usable as a highly intensified imaging agent for cancer diagnosis. Moreover, they can be applied as photothermal agents for the in vitro killing of MCF-7 cells and the in vivo ablation of tumors, which were constructed on the bodies of nude mice. MCF-7 cells almost quantitatively die after they are incubated with the QDs (at 100 mu g mL(-1)) for 2 h and irradiated under an 808 nm laser at a power density of 1.0 W cm(-2) for 10 min. The tumors on the nude mice can also be effectively ablated without regrowth during the period of observation (at least 20 d) after PTT.