Motivation: The unique microenvironment of tumors making detection of microenvironmental alterations a valuable asset for early diagnosis of tumors. Goal(s): This study focuses on exploring impact of Fe3O4 NPs on changes in the tumor microenvironment's acidity. Approach: By combining them with CEST exogenous contrast agent, we evaluated the feasibility of dual-contrast imaging. Results: In vitro MRI results suggest that Fe3O4 NPs can act as stable reference agents under varying pH conditions, providing negative contrast for T2-weighted MRI. The CEST effect shows a strong correlation with pH, allowing for quantitative assessment of pH shifts in tumor microenvironment, and can be controlled by adjusting Fe3O4 concentration. Impact: These preliminary findings represent an initial stride toward dual-contrast imaging involving CEST and T2 contrast agents, with the potential for further expansion in future in vivo investigations.

Concurrent Dual-Contrast Enhancement Using Fe3O4 Nanoparticles to Achieve a CEST Signal Controllability