Luminescent Silica Nanosensors for Lifetime Based Imaging of Intracellular Oxygen with Millisecond Time Resolution.

Intracellular oxygen concentration was quantitatively imaged and rapidly traced with millisecond time resolution. We have demonstrated a new kind of oxygen nanosensors based on a ruthenium complex doped solid silica nanoparticles, which showed high oxygen sensing performance (I0/I100 = 3.29, t95 < 3 s) and ease of surface functionalization. Their sensing performance can be tuned by changing types of oxygen-sensitive probes and particle morphology. The nanosensors showed excellent control in both sensor size (from 30 to 200 nm), monodispersity, morphology, surface chemistry, and batch to batch consistency. Their uniform size distribution and good biocompatibility made them suitable for intracellular studies. Because the sensor surface can be easily functionalized with arbitrary units (such as transmembrane motifs, drugs, organelle-targeting groups, imaging reagent, and multiple sensor probes), these nanosensors provide a general platform to build easy-to-use tools for intracellular applications. The ease of surface functionalization was demonstrated by modifying the sensors outer surface with morpholinopropylamine and (3-carboxypropyl) triphenyl phosphonium, to actively target intracellular lysosomes and mitochondria of the tested cell lines (HeLa, MCF-7, and MCF-10A). Applying the mitochondria-targeting oxygen nanosensor together with our custom-built rapid phosphorescent lifetime imaging system, variations of intracellular oxygen have been quantitatively imaged and traced (in millisecond intervals) in real time and in situ.