High relaxivity Gd(III)-DNA gold nanostars: Investigation of shape effects on proton relaxation

Matthew W. Rotz, Kayla S.B. Culver, Giacomo Parigi, Keith W. Macrenaris, Claudio Luchinat, Teri W. Odom, Thomas J. Meade*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

87 Scopus citations


Gadolinium(III) nanoconjugate contrast agents (CAs) have distinct advantages over their small-molecule counterparts in magnetic resonance imaging. In addition to increased Gd(III) payload, a significant improvement in proton relaxation efficiency, or relaxivity (r1), is often observed. In this work, we describe the synthesis and characterization of a nanoconjugate CA created by covalent attachment of Gd(III) to thiolated DNA (Gd(III)-DNA), followed by surface conjugation onto gold nanostars (DNA-Gd@stars). These conjugates exhibit remarkable r1 with values up to 98 mM-1 s-1. Additionally, DNA-Gd@stars show efficient Gd(III) delivery and biocompatibility in vitro and generate significant contrast enhancement when imaged at 7 T. Using nuclear magnetic relaxation dispersion analysis, we attribute the high performance of the DNA-Gd@stars to an increased contribution of second-sphere relaxivity compared to that of spherical CA equivalents (DNA-Gd@spheres). Importantly, the surface of the gold nanostar contains Gd(III)-DNA in regions of positive, negative, and neutral curvature. We hypothesize that the proton relaxation enhancement observed results from the presence of a unique hydrophilic environment produced by Gd(III)-DNA in these regions, which allows second-sphere water molecules to remain adjacent to Gd(III) ions for up to 10 times longer than diffusion. These results establish that particle shape and second-sphere relaxivity are important considerations in the design of Gd(III) nanoconjugate CAs.

Original languageEnglish (US)
Pages (from-to)3385-3396
Number of pages12
JournalACS nano
Issue number3
StatePublished - Mar 24 2015


  • contrast agent
  • gadolinium
  • magnetic resonance
  • nanostar
  • nuclear magnetic resonance dispersion
  • relaxivity
  • second-sphere

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)


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