Gadolinium(III) Di- and Tetrachelates Designed for in Vivo Noncovalent Complexation with Plasma Proteins: A Novel Molecular Design for Blood Pool MRI Contrast Enhancing Agents

Abstract

A new series of gadolinium chelates designed as blood pool contrast enhancing agents for magnetic resonance imaging applications is described. Complexes having four Gd(III) chelate units display a significant increase in molecular relaxivity per gadolinium ion in water (9-13 L x mmol(-1) x (s-1) compared to Gd(III)-DTPA (5 L x mmol(-1) x s(-1). A further jump in relaxivity (25 L x mmol(-1) x sec(-1) in 4% BSA solution was observed in the case of a fatty acid-containing tetrachelate and is attributed to noncovalent binding of the tetrachelate to serum albumin. This agent was successfully used for imaging the rat circulatory system.