Improved Stability and Photothermal Performance of Polydopamine‐Modified Fe3O4 Nanocomposites for Highly Efficient Magnetic Resonance Imaging‐Guided Photothermal Therapy

Abstract Magnetic nanomaterials are a promising class of contrast agents for magnetic resonance imaging (MRI). However, their poor stability and low relaxivity are major challenges hindering their clinical applications. In this study, magnetic theranostic nanoagents based on polydopamine‐modified Fe 3 O 4 (Fe 3 O 4 @PDA) nanocomposites are fabricated for MRI‐guided photothermal therapy (PTT) cancer treatments. Their high transverse relaxivity of 337.8 mM −1 s −1 makes these Fe 3 O 4 @PDA nanocomposites a promising T 2 ‐weighted MRI contrast agent for cancer diagnosis and image‐guided cancer therapy. Due to the good photothermal effect of polydopamine (PDA), the tumors of 4T1 tumor‐bearing mice are completely excised by PTT. Most importantly, the PDA shell also improves the stability of the Fe 3 O 4 @PDA nanocomposites, which contributes to their excellent, long‐term performance in MRI and PTT applications. Their good stability, high T 2 relaxivity, robust biocompatibility, and satisfactory treatment effect give these Fe 3 O 4 @PDA nanocomposites great potential for use in cancer theranostics.