Mitochondria-Targeted Fluorescent and Photoacoustic Imaging of Hydrogen Peroxide in Inflammation

Hydrogen peroxide (H₂O₂) is a prominent reactive oxygen species with relative stability, which makes it a potential diagnostic marker for pathological states. Excessive H₂O₂ in mitochondria leads to oxidative stress and inflammation. However, precisely monitoring the level of H₂O₂ at specific organelles (e.g., mitochondria) in vivo is still of urgent necessity. Therefore, we rationally designed a mitochondria-targeted near-infrared probe TPP-HCy-BOH for fluorescent/photoacoustic (FL/PA) dual-modal imaging of overproduced H₂O₂ in an inflamed mouse model. TPP-HCy-BOH had a low LOD (0.348 μM), which is comparable to those of recently reported probes for H₂O₂ detection. The high kinetic rate constant (k_obs = 4.72 × 10^-3 s^-1) of TPP-HCy-BOH toward H₂O₂ is superior to recently reported H₂O₂ probes. Compared to control probe HCy-BOH without the mitochondrial targeting moiety, TPP-HCy-BOH successfully images exogenous or endogenous H₂O₂ in mitochondria with an additional 2.4-fold FL increase and 4.7-fold PA increase in HeLa cells or additional 2.1-fold FL increase and 3.3-fold PA increase in RAW 264.7 cells. In LPS-induced acute inflammation in vivo, TPP-HCy-BOH is more competent to image overproduced H₂O₂ with additional 1.6-fold higher sensitivity of FL in abdomen and 2.0-fold higher sensitivity of PA in liver and longer retention time of 0.5 h than HCy-BOH. We anticipate that TPP-HCy-BOH could be employed for the FL/PA dual-modal diagnosis of pathological inflammation in clinic in near future.