Fluorescent Ruby Nanocrystals For Biocompatible Applications

Chromium-doped aluminum oxide (ruby) micro- and nanocrystals have shown a sharp and strong fluorescence emission that linearly depends on pressure and temperature. They also have an exceptional photostability and a high quantum efficiency. In spite of their widespread use as pressure sensors, only a few earlier studies have used ruby nanocrystals as efficient fluorescent bioimaging probes. However, their use at biocompatible excitation/detection wavelengths and toxicity assessment against human living cells remain unexplored. In this work, we show that ruby nanocrystals can be efficiently excited and detected within the biological transparency window. We also examined the biocompatibility of ruby nanocrystals in human living cells, which exhibited no detectable cytotoxicity. This makes ruby nanocrystals among the best alternative fluorescent probes for promising biological applications.