Simultaneous Nanothermometry and Deep-Tissue Imaging.

Bright, stable, and biocompatible fluorescent contrast agents operating in the second biological window (1000-1350 nm) are attractive for imaging of deep-lying structures (e.g., tumors) within tissues. Ideally, these contrast agents also provide functional insights, such as information on local temperature. Here, water-dispersible barium phosphate nanoparticles doped with Mn5+ are made by scalable, continuous, and sterile flame aerosol technology and explored as fluorescent contrast agents with temperature-sensitive peak emission in the NIR-II (1190 nm). Detailed assessment of their stability, toxicity with three representative cell lines (HeLa, THP-1, NHDF), and deep-tissue imaging down to about 3 cm are presented. In addition, their high quantum yield (up to 34%) combined with excellent temperature sensitivity paves the way for concurrent deep-tissue imaging and nanothermometry, with biologically well-tolerated nanoparticles.

Silica-Coated TiN Particles for Killing Cancer Cells.

Photothermal therapy (PTT) using plasmonic nanoparticles for cancer treatment is on the verge of clinical application. Titanium nitride (TiN) nanoparticles offer a promising alternative to commonly used gold-based systems at a fraction of the costs. Little is known, however, about the relationship between TiN particle characteristics and their optical properties in colloidal systems. Here, TiN nanoparticles with closely controlled characteristics are prepared by nitridation of TiO2, and their use as PTT agents is explored. Emphasis is placed on the particle surface and core oxygen content, which dominate the TiN optical properties. Colloidal suspensions were studied under UV-vis and near-infrared (NIR) laser irradiation and correlated to particle characteristics. High nitridation temperatures and long residence times lead to increased NIR light absorption. Too high nitridation temperatures, however, lead to particle aggregation that deteriorated their optical properties. This was overcome with SiO2 coating of TiO2 nanoparticles prior to nitridation: the resulting SiO2-coated TiN particles exhibited increased plasmonic performance compared to bare TiN, which is attributed to reduced plasmonic coupling effects. The optimized SiO2-coated TiN had a photothermal efficiency of 58.5% and mass extinction coefficient of 31.6 L g-1 cm-1, outperforming commercial gold nanoshells that are used in clinical trials. The potential of SiO2-coated TiN for photothermal therapy was demonstrated by controllably killing HeLa cells in vitro.