Advantages of macromolecular to nanosized chemical-exchange saturation transfer agents for MRI applications.

Chemical-exchange saturation transfer (CEST) agents are a new class of MRI contrast agents that offer a number of advantages over conventional Gd(3+) agents. Over the past few years, a variety of small-molecule CEST agents responsive to physiological conditions, such as pH and temperature, have been designed and their imaging applications have been reported. One of the major drawbacks of current small-molecule CEST agents is their relatively low sensitivity.