Search

The encapsulation and/or surface modification can stabilize and protect the phosphorescence bio‐probes but impede their intravenous delivery across biological barriers. Here, a new class of biocompatible rhenium (ReI) diimine carbonyl complexes is developed, which can efficaciously permeate normal vessel walls and then functionalize the extravascular collagen matrixes as in situ oxygen sensor. Without protective agents, ReI‐diimine complex already exhibits excellent emission yield (34%, λ em = 583 nm) and large two‐photon absorption cross‐sections (σ 2 = 300 GM @ 800 nm) in water (pH 7.4). After extravasation, remarkably, the collagen‐bound probes further enhanced their excitation efficiency by increasing the deoxygenated lifetime from 4.0 to 7.5 µs, paving a way to visualize tumor hypoxia and tissue ischemia in vivo. The post‐extravasation functionalization of extracellular matrixes demonstrates a new methodology for biomaterial‐empowered phosphorescence sensing and imaging., Biocompatible rhenium (ReI) diimine carbonyl complexes functionalize the extravascular collagen matrixes as in situ oxygen sensor. After tail‐vein delivery and vessel penetration, the probe can bind extravascular collagens and achieve stabilization enhanced two‐photon phosphorescence yields. Increased deoxygenated phosphorescence lifetime from 4.0 to 7.5 µs paves a way to visualize tumor hypoxia and tissue ischemia in vivo.