TY - JOUR
T1 - A chemical strategy for the relaxivity enhancement of GdIII chelates anchored on mesoporous silica nanoparticles
AU - Carniato, Fabio
AU - Tei, Lorenzo
AU - Cossi, Maurizio
AU - Marchese, Leonardo
AU - Botta, Mauro
PY - 2010/9/17
Y1 - 2010/9/17
N2 - Functionalised MCM-41 mesoporous silica nanoparticles were used as carriers of GdIII complexes for the development of nanosized magnetic resonance imaging contrast agents. Three GdIII complexes based on the 1,4,7,10-tetraazacyclododecane scaffold (DOTA; monoamide-, DOTA- and DO3A-like complexes) with distinct structural and magnetic properties were anchored on the silica nanoparticles functionalised with NH2 groups. The interaction between GdIII chelates and surface functional groups markedly influenced the relaxometric properties of the hybrid materials, and were deeply modified passing from ionic - NH3+ to neutral amides. A complete study of the structural, textural and surface properties together with a full 1H relaxometric characterisation of these hybrid materials before and after surface modification was carried out. Particularly for the anionic complex 2 attached to MCM-41, an impressive increase in relaxivity (r1p) was observed (from 20.3 to 37.8 mM-1 s-1, 86.2% enhancement at 20 MHz and 310 K), mainly due to a threefold faster water exchange rate after acetylation of the surface -NH3+ ions. This high r1p value, coupled with the large molar amount of grafted 2 onto the silica nanoparticles gives rise to a value of relaxivity per particle of 29500 mM-1 s-1, which possibly allows it to be used in molecular imaging procedures. Smaller changes were observed for the hybrid materials based on neutral 1 and 3 complexes. In fact, whereas 1 shows a weak interaction with the surface and acetylation induced only some decrease of the local rotation, complex 3 appears to be involved in a strong interaction with surface silanols. This results in the displacement of a coordinated water molecule and in a decrease of the accessibility of the solvent to the metal centre, which is unaffected by the modification of ammonium ions to neutral amides.
AB - Functionalised MCM-41 mesoporous silica nanoparticles were used as carriers of GdIII complexes for the development of nanosized magnetic resonance imaging contrast agents. Three GdIII complexes based on the 1,4,7,10-tetraazacyclododecane scaffold (DOTA; monoamide-, DOTA- and DO3A-like complexes) with distinct structural and magnetic properties were anchored on the silica nanoparticles functionalised with NH2 groups. The interaction between GdIII chelates and surface functional groups markedly influenced the relaxometric properties of the hybrid materials, and were deeply modified passing from ionic - NH3+ to neutral amides. A complete study of the structural, textural and surface properties together with a full 1H relaxometric characterisation of these hybrid materials before and after surface modification was carried out. Particularly for the anionic complex 2 attached to MCM-41, an impressive increase in relaxivity (r1p) was observed (from 20.3 to 37.8 mM-1 s-1, 86.2% enhancement at 20 MHz and 310 K), mainly due to a threefold faster water exchange rate after acetylation of the surface -NH3+ ions. This high r1p value, coupled with the large molar amount of grafted 2 onto the silica nanoparticles gives rise to a value of relaxivity per particle of 29500 mM-1 s-1, which possibly allows it to be used in molecular imaging procedures. Smaller changes were observed for the hybrid materials based on neutral 1 and 3 complexes. In fact, whereas 1 shows a weak interaction with the surface and acetylation induced only some decrease of the local rotation, complex 3 appears to be involved in a strong interaction with surface silanols. This results in the displacement of a coordinated water molecule and in a decrease of the accessibility of the solvent to the metal centre, which is unaffected by the modification of ammonium ions to neutral amides.
KW - Gadolinium
KW - Imaging agents
KW - Mesoporous materials
KW - Nanostructures
KW - Relaxivity
UR - http://www.scopus.com/inward/record.url?scp=77956640642&partnerID=8YFLogxK
U2 - 10.1002/chem.201000499
DO - 10.1002/chem.201000499
M3 - Article
SN - 0947-6539
VL - 16
SP - 10727
EP - 10734
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 35
ER -