Macrocyclic Pyclen-Based Hybrid Nanoprobes for Magnetic Resonance Imaging of Sentinel Lymph Node Metastasis

The clinical diagnosis of sentinel lymph node (SLN) metastasis through contrast-enhanced magnetic resonance imaging (MRI) remains challenging. In this work, a pyclen-based amphiphilic gadolinium chelate (GdL) was developed and coassembled with DSPE-PEG2000 to form hybrid micelles for SLN metastasis imaging. The micelles exhibited high relaxivity and kinetic stability, with particle size and relaxivity adjustable by modifying the DSPE-PEG/GdL mass ratio. The DSPE-PEG/GdL micelles (15:1) displayed the highest T 1 relaxivity (23.5 Gd mM –1 s –1 at 1.5 T), which is 5.6-fold greater than that of Gd-DOTA, coupled with high kinetic stability. In a mouse model of breast cancer lymph node metastasis, SLN was successfully distinguished at a much lower dosage (0.75 or 1.5 mg Gd kg –1 BW) compared to the clinical dose of 15.7 mg Gd kg –1 BW, as evidenced by differences in MR signal intensity. Overall, the strategy of coassembling pyclen-based Gd chelates with DSPE-PEG2000 offers a feasible approach for developing effective MR probes for lymph node metastasis imaging.