NaGdF ₄ nanoparticle-based molecular probes for magnetic resonance imaging of intraperitoneal tumor xenografts in vivo

Differently sized NaGdF ₄ nanocrystals with narrow particle size distributions were synthesized by a high temperature approach. Upon ligand exchange, the as-prepared hydrophobic NaGdF ₄ nanocrystals were transferred into water by using asymmetric PEGs simultaneously bearing phosphate and maleimide groups. Further investigations demonstrated that the water-soluble NaGdF ₄ nanocrystals, coated by PEG bearing two phosphate groups on the same side, exhibit not only excellent colloidal stability in water and PBS buffer, but also higher T1 relaxivity than Gd-DTPA (Magnevist). Through "click" reaction between the maleimide residue on particle surface and thiol group from the partly reduced anti-EGFR monoclonal antibody (mAb), NaGdF ₄ -PEG-mAb nanoprobes were constructed, and their biocompatibility and binding specificity were evaluated through in vitro experiments. A series of in vivo experiments were then carried out for detecting intraperitoneal tumor xenografts in nude mice by using magnetic resonance (MR) imaging technique. The results revealed that the NaGdF ₄ -PEG-mAb probes possessed satisfying tumor-specific targeting ability and strong MR contrast enhancement effects.