Toward design of magnetic nanoparticle clusters stabilized by biocompatible diblock copolymers for T₂-weighted MRI contrast.
We report the fabrication of magnetic particles comprised of clusters of iron oxide nanoparticles, 7.4 nm mean diameter, stabilized by a biocompatible, amphiphilic diblock copolymer, poly(ethylene oxide-b-D,L-lactide). Particles with quantitative incorporation of up to 40 wt % iron oxide and hydrodynamic sizes in the range of 80-170 nm were prepared. The particles consist of hydrophobically modified iron oxide nanoparticles within the core-forming polylactide block with the poly(ethylene oxide) forming a corona to afford aqueous dispersibility. The transverse relaxivities (r2) increased with average particle size and exceeded 200 s(-1) mM Fe(-1) at 1.4 T and 37 °C for iron oxide loadings above 30 wt %. These experimental relaxivities typically agreed to within 15% with the values predicted using analytical models of transverse relaxivity and cluster (particle core) size distributions derived from cryo-TEM measurements. Our results show that the theoretical models can be used for the rational design of biocompatible MRI contrast agents with tailored compositions and size distributions.
Macromolecules and Interfaces Institute, ‡Department of Chemistry, and §Department of Chemical Engineering, Virginia Tech , Blacksburg, Virginia 24061, United States.
Sharavanan
S
Balasubramaniam
Sanem
S
Kayandan
Yin-Nian
YN
Lin
Deborah F
DF
Kelly
Michael J
MJ
House
Robert C
RC
Woodward
Timothy G
TG
St Pierre
Judy S
JS
Riffle
Richey M
RM
Davis
D003287:Contrast Media / Q000138:chemical synthesis / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011091:Polyesters / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization
D003287:Contrast Media; D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; D011091:Polyesters; C000499:ferric oxide; D011092:Polyethylene Glycols; C033616:poly(lactide)