A targeted antiferromagnetic nanoprobe for ultra‐sensitive magnetic resonance imaging detection of sub‐millimeter esophageal tumors

Abstract Early, non‐invasive detection of esophageal cancer at sub‐millimeter resolution is critical for tailoring precise therapeutic strategies. While ultra‐high‐field (UHF) magnetic resonance imaging (MRI) offers exceptional spatial resolution, the lack of optimized contrast agents capable of enhancing sensitivity for detecting microscopic tumors remains a significant challenge. Here, we report a cyclo‐RGD peptide‐conjugated antiferromagnetic nanoparticle (RANP) as a novel targeted T 1 contrast agent, specifically designed to improve in vivo imaging of esophageal tumors at the micrometer scale. The RANP integrates an antiferromagnetic core with low magnetization, minimizing T 2 decaying effects, while the cyclo‐RGD peptide enhances its targeting ability by specifically binding to integrin α v β 3 , a biomarker highly expressed on tumor vasculature. This targeted conjugation improves the probe's selective accumulation at the tumor site and facilitates superior T 1 relaxation of water protons. Under 9 T MRI conditions, the RANP exhibits an r 1 value of 1.88 mM −1 s −1 and a low r 2/ r 1 ratio of 1.84, enabling the detection of primary esophageal tumors as small as 0.8 mm. This study significantly advances the sensitivity of current imaging techniques, pushing the detection limit of in vivo esophageal cancer diagnosis into the sub‐millimeter range. Our results demonstrate the promising potential of RANP‐enhanced UHF MRI for early detection, monitoring, and therapeutic intervention in esophageal cancer, offering a powerful tool for more effective clinical management.