Gold nanoparticles functionalised with stable, fast water exchanging Gd3+ chelates as high relaxivity contrast agents for MRI.

Gold nanoparticles functionalized with Gd(3+) chelates displaying fast water exchange, superb pH stability and inertness towards transmetalation with Zn(2+) have been prepared and characterized as a new high relaxivity (29 mM(-1) s(-1), 30 MHz, 25 °C) contrast agent potentially safe for in vivo MRI applications. The Lipari-Szabo treatment for internal rotation was used to evaluate the effect of linker flexibility on the relaxivity of the gold nanoparticles. The effect of fast water exchange on the relaxivity of gold nanoparticles functionalized with Gd(3+) chelates is also addressed in this communication.