Hydrogen Sulfide-Responsive MRI Probe for Imaging Colon Cancer in Mice.

Hydrogen sulfide (H2S), a significant gaseous signaling molecule, is highly expressed in colon cancer. However, realizing highly sensitive and specific imaging of H2S in deep colon cancer tissues remains an important challenge. In order to overcome this limitation, we have developed a H2S-responsive magnetic probe (HRMP) with a high sensitivity and specificity. HRMP is synthesized using superparamagnetic iron oxide and Mn-porphyrin, coated with a hydrogen sulfide-responsive polymer. Upon reaction with H2S, the released nanoparticles aggregate, producing an enhanced transverse relaxivity (r2) through the dipolar effect. Incorporation of an ortho azide group ensures that HRMP specifically responds to H2S, reacting swiftly within 2 h to induce a change in T2 relaxation time. Additionally, by precisely tuning the feeding ratio of Mn-porphyrin to iron oxide, HRMP was endowed with high sensitivity, achieving a detection limit as low as 8.7 μM. In studies with HCT116 colon cancer, where H2S is overexpressed, HRMP generated a distinct negative contrast at the tumor site. HRMP shows potential for in vivo imaging of colon cancer, offering promise for the early diagnosis of tumors.