Abstract
Chemical-exchange saturation transfer (CEST) agents are a new class of MRI contrast agents that offer a number of advantages over conventional Gd3+ 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. The advantages of using macromolecular and nanosized systems with large numbers of exchangeable groups to improve contrast sensitivity are highlighted in this brief review. Although this approach has been shown to amplify contrast sensitivity, other limitations, including relatively small chemical-shift differences between the exchanging species and bulk water and less than optimal proton exchange rates, still exist. By addressing these issues, it is anticipated that CEST agents will find useful applications in the detection of specific biomarkers of disease.
Financial & competing interests disclosure
The authors thank the financial support from the NIH (CA-115531, CA-126608, RR-02584 and EB-04582) and the Robert A. Welch Foundation (AT-584). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.