Magnetic Resonance Diagnosis of Early Triple-Negative Breast Cancer Based on the Ionic Covalent Organic Framework with High Relaxivity and Long Retention Time

Patients with triple-negative breast cancer (TNBC) havedismalprognoses due to the lack of therapeutic targets and susceptibilityto lymph node (LN) metastasis. Therefore, it is essential to developmore effective approaches to identify early TNBC tissues and LNs.In this work, a magnetic resonance imaging (MRI) contrast agent (Mn-iCOF)was constructed based on the Mn-(II)-chelated ionic covalent organicframework (iCOF). Because of the porous structure and hydrophilicity,the Mn-iCOF has a high longitudinal relaxivity (r (1)) of 8.02 mM(-1) s(-1) at 3.0 T. For the tumor-bearing mice, a lower dose (0.02 mmol [Mn]/kg)of Mn-iCOF demonstrated a higher signal-to-noise ratio (SNR) value(1.8) and longer retention time (2 h) compared to a 10-fold dose ofcommercial Gd-DOTA (0.2 mmol [Gd]/kg). Moreover, the Mn-iCOF can providecontinuous and significant MR contrast for the popliteal LNs within24 h, allowing for accurate evaluation and dissection of LNs. Theseexcellent MRI properties of the Mn-iCOF may open new avenues for designingmore biocompatible MRI contrast agents with higher resolutions, particularlyin the diagnosis of TNBC.