Rational design for enhancing inflammation-responsive in vivo chemiluminescence via nanophotonic energy relay to near-infrared AIE-active conjugated polymer

Abstract H 2 O 2 -specific peroxalate chemiluminescence is recognized as a potential signal for sensitive in vivo imaging of inflammation but the effect of underlying peroxalate-emitter energetics on its efficiency has rarely been understood. Here we report a simple nanophotonic way of boosting near-infrared chemiluminescence with no need of complicated structural design and synthesis of an energetically favored emitter. The signal enhancement was attained from the construction of a nanoparticle imaging probe (∼26 nm in size) by dense nanointegration of multiple molecules possessing unique photonic features, i.e., i) a peroxalate as a chemical fuel generating electronic excitation energy in response to inflammatory H 2 O 2 , ii) a low-bandgap conjugated polymer as a bright near-infrared emitter showing aggregation-induced emission (AIE), and iii) an energy gap-bridging photonic molecule that relays the chemically generated excitation energy to the emitter for its efficient excitation. From static and kinetic spectroscopic studies, a green-emissive BODIPY dye has proven to be an efficient relay molecule to bridge the energy gap between the AIE polymer and the chemically generated excited intermediate of H 2 O 2 –reacted peroxalates. The energy-relayed nanointegration of AIE polymer and peroxalate in water showed a 50-times boosted sensing signal compared to their dissolved mixture in THF. Besides the high H 2 O 2 detectability down to 10 −9  M, the boosted chemiluminescence presented a fairly high tissue penetration depth (>12 mm) in an ex vivo condition, which enabled deep imaging of inflammatory H 2 O 2 in a hair-covered mouse model of peritonitis.