Gd-functionalised Au nanoparticles as targeted contrast agents in MRI: relaxivity enhancement by polyelectrolyte coating

Monolayer-protected, Gd3+-functionalised gold nanoparticles with enhanced spin-lattice relaxivity (r(1)) were prepared; adsorption of polyelectrolytes on these materials further increased r(1) and ligand exchange with a biotin-derivatised disulfide led to a prototype avidin-targeted contrast agent.