Storable, thermally activated, near-infrared chemiluminescent dyes and dye-stained microparticles for optical imaging

Abstract

Optical molecular imaging employs relatively harmless, low-energy light and technically straightforward instrumentation. Self-illuminating, chemiluminescent systems are especially attractive since they have inherently high signal contrast due to the lack of background emission. Currently, chemiluminescence imaging involves short-lived molecular species that are not stored but instead generated in situ, and they typically emit visible light, which does not penetrate far through heterogeneous biological media. Here, we describe a new paradigm for optical molecular imaging using squaraine rotaxane endoperoxides (SREPs), interlocked fluorescent and chemiluminescent dye molecules that have a squaraine chromophore encapsulated inside a macrocycle endoperoxide. SREPs can be stored indefinitely at temperatures below −20 °C, but upon warming to body temperature they undergo a unimolecular chemical reaction and emit near infrared light that can pass through a living mouse. Dye-stained microparticles are easily prepared for in vivo near-infrared optical imaging using commercial imaging stations.