Traditional texaphyrin exhibits merits like long absorption wavelength, high light absorption and light quenching coefficients. The paramagnetic cationic manganese located in the center of texaphyrin serving as a fluorescence quenching agent can further enhance the photoacoustic effect of Manganese texaphyrin (MMn) near infrared region.  

Based on the self-developed near-infrared photoacoustic molecular imaging technology, a team led by Dr. LIU Chengbo from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences had realized tumor-specific photoacoustic molecular imaging both in vitro and in vivo. 

Recently, the team and their collaborators from University of Texas at Austin explored the photoacoustic imaging mechanism of paramagnetic metalloporphyrins.  

They found that with the manganese metal being the center, the texaphyrin MMn showed the properties of paramagnetism, strong absorption, no fluorescence emission loss, and specific protein binding synergistic effects. These properties could contribute to a new photoacoustic molecular imaging system and strategy for preliminary exploration and realization of specific 3D photoacoustic molecular imaging of tumors. 

Additionally, MMn could react with reactive oxygen species and other superoxides to effectively inhibit oxidative stress injury within the body, accompanied by changes in near-infrared photoacoustic characteristics. Therefore, MMn can also be used as an indicator and inhibitor for the study of oxidative stress intensity and damage in vivo.  

The next step of the research is continuing to explore the application of MMn in scientifically research of brain to study the oxidative stress response in a variety of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, cerebral ischemia, brain injury, and epilepsy. 

The study entitled "Manganese(II) Texaphyrin: A Paramagnetic Photoacoustic Contrast Agent Activated by Near-IR Light" was published in Journal of the American Chemical Society. 

(a) Molecular structure of MMn and its photoacoustic properties; (b) Photoacoustic signal and stability of MMn within tumors (Image by SIAT)