Tumor microenvironment-triggered fabrication of gold nanomachines for tumor-specific photoacoustic imaging and photothermal therapy† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc00700k Click here for additional data file.

Experimental Section: Materials. Alpha-cyclodextrin (α-CD) was purchased from Sigma Chemical Company. Trisodium citrate (C6H5Na3O7·2H2O) and hydrogen tetrachloroaurate(III) (HAuCl4·4H2O) were purchased from China National Pharmaceutical Group Corporation (Shanghai, China). All the chemicals were of analytical grade and were used without further purification. Sartorius ultrapure water (18.2 MΩ·cm, Milli-Q, Millipore) was used throughout the experiments. DNA oligonucleotides were synthesized and purified by TAKARA Biotechnology (Dalian, China). The human breast cancer cell line (MCF-7) was purchased from KeyGEN Biotechnology Company (Nanjing, China). Instruments. High-resolution transmission electron microscopy (HRTEM) was carried out on a JEM-2100 electron microscope. The absorption spectra were collected on a PharmaSpec UV-1700 UV-vis spectrophotometer (Shimadzu, Japan). All pH measurements were performed with a pH3c digital pH meter (Shanghai LeiCi Device Works, Shanghai, China) equipped with a combined glass-calomel electrode. The sections were observed through a Nikon Eclipse 80i microscope (200×). Photoacoustic images were obtained at 808 nm using a PA tomography system (Endra Nexus 128, Ann Arbor, MI).