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 (<i>r</i>₂) 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 <i>T</i>₂ 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.