Degradable Semiconducting Oligomer Amphiphile for Ratiometric Photoacoustic Imaging of Hypochlorite

Upregulation of highly reactive oxygen species (ROS) such as hypochlorite (ClO-) is associated with many pathological conditions including cardiovascular diseases, neuron degeneration, lung injury, and cancer. However, real-time imaging of ClO- is limited to the probes generally relying on fluorescence with shallow tissue penetration depth. We here propose a self-assembly approach to develop activatable and degradable photo acoustic (PA) nanoprobes for in vivo imaging of ClO-. A near-infrared absorbing amphiphilic oligomer is synthesized to undergo degradation in the presence of a specific ROS (ClO-), which integrates a pi-conjugated but ClO- oxidizable backbone with hydrophilic PEG side chains. This molecular architecture allows the oligomer to serve as a degradable nanocarrier to encapsulate the ROS-inert dye and self-assemble into structurally stable nanoparticles through both pi-pi stacking and hydrophobic interactions. The self-assembled nanoprobe exhibits sensitive and specific ratiometric PA signals toward ClO-, permitting ratiometric PA imaging of ClO- in the tumor of living mice.