Nanoassembled capsules as delivery vehicles for large payloads of high relaxivity Gd3+ agents

J Am Chem Soc. 2009 Nov 4;131(43):15918-23. doi: 10.1021/ja906981w.


Nanoassembled capsules (NACs) that incorporate a polymer aggregate inside a silica shell may be loaded with agents that are of particular interest for therapeutic or diagnostic applications. NACs formed using the MRI contrast agent GdDOTP(5-) in the internal polymer aggregate are reported herein, the smaller of which show promise as potential MRI contrast agents. Unlike many other nanoencapsulated systems, water access to the inner core of these NACs does not appear to be limited and consequently the water relaxivity per Gd(3+) agent can reach as high as 24 mM(-1) s(-1). Robust, spherical capsules were formed using polyallylamine or poly-L-lysine ranging from 0.2 to 5 microm in diameter. The greatest gains in relaxivity were observed for smaller NACs, for which water accessibility remained high but molecular rotation of the Gd(3+) chelate was effectively restricted. Larger NACs did not afford such large gains in relaxivity, the result of poorer water accessibility combined with less-effective rotational restriction.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Drug Delivery Systems*
  • Microscopy, Electron, Scanning
  • Microscopy, Electron, Transmission
  • Nanocapsules*
  • Organometallic Compounds / administration & dosage*
  • Organophosphorus Compounds / administration & dosage*


  • Nanocapsules
  • Organometallic Compounds
  • Organophosphorus Compounds
  • gadolinium-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetrakis(methylenephosphonic acid)