Original ArticleCharacteristics of a New MRI Contrast Agent Prepared From Polypropyleneimine Dendrimers, Generation 2Wang, Steven J. MS*‡; Brechbiel, Martin PhD; Wiener, Erik C. PhDAuthor Information From the *Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana–Champaign, Illinois; †The Beckman Institute, University of Illinois at Urbana–Champaign, Illinois; the ‡Biomedical Magnetic Resonance Laboratory, College of Medicine, University of Illinois at Urbana–Champaign, Illinois; the §Department of Molecular and Integrative Physiology, University of Illinois at Urbana–Champaign, Illinois; the ¶Department of Medical Information Science, University of Illinois at Chicago, Illinois; and the ∥National Cancer Institute, National Institutes of Health, Bethesda, Maryland. Received August 8, 2001, and accepted for publication, after revision, April 25, 2003. Supported by grants from the National Institutes of Health PHS 1 R29 C61918, PHS 5 P41 RR05964, and IS10RR06243. Correspondence to: Erik Wiener, PhD, University of Pittsburgh Cancer Institute, Hillman Cancer Center, 5117 Centre Avenue, Room 2.26, Pittsburgh, PA [email protected] Investigative Radiology: October 2003 - Volume 38 - Issue 10 - p 662-668 doi: 10.1097/01.rli.0000084887.47427.75 Buy Metrics Abstract Rationale and objectives: Dendrimer-based magnetic resonance imaging (MRI) contrast agents offer many advantages including high levels of amplification. The objective of this research was to test the adequacy and viability of a new family of dendrimers for use as MRI contrast agents in vitro and in vivo. Methods: Dendrimers based on 1,4-diaminobutane core polypropyleneimine (PPI) generation 2 and ammonia core polyamidoamine dendrimers had the free surface amines conjugated to a diethylenetriaminepentaacetic acid derivative followed by complex formation with gadolinium. Relaxivity measurements were made on an IBM Field Cycling Relaxometer. Biodistribution and pharmacokinetic studies were examined with the radiotracer 153Gd in rats and a counting window of 95 to 105 keV. MRI images were conducted at 4.7 T. Results: The relaxivity of the PPI agent exceeded that of the corresponding generation polyamidoamine (PAMAM) agent. Uptake occurred in the liver, spleen, and kidney. Pharmacokinetic studies showed a biexponential decay with excretion half-lives of 3 hours and 33.6 days respectively. The agent increased the contrast enhancement, 1 hour after injection, of T1-weighted images by 52%. Conclusions: This PPI agent resulted in significant contrast signal enhancement. This family of agent may also provide a valuable contrast agent backbone. © 2003 Lippincott Williams & Wilkins, Inc.