We present a series of hydrogel nanoparticles (nanogels) incorporating either acyclic or cyclic gadolinium chelates as crosslinkers. These crosslinkers are used to formulate polyacrylamide-based nanogels (diameter 50 to 85 nm) yielding contrast agents with enhanced relaxivities (up to 6-fold greater than Dotarem®), because the nanogel structure slows the chelator's tumbling frequency and allows fast water exchange. Importantly, ...
