Tuning the magnetic resonance imaging properties of positive contrast agent nanoparticles by surface modification with RAFT polymers.
A novel surface modification technique was employed to produce a polymer modified positive contrast agent nanoparticle through attachment of well-defined homopolymers synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A range of RAFT homopolymers including poly[N-(2-hydroxypropyl)methacrylamide], poly(N-isopropylacrylamide), polystyrene, poly(2-(dimethylamino)ethyl acrylate), poly(((poly)ethylene glycol) methyl ether acrylate), and poly(acrylic acid) were synthesized and subsequently used to modify the surface of gadolinium (Gd) metal-organic framework (MOF) nanoparticles. Employment of a trithiocarbonate RAFT agent allowed for reduction of the polymer end groups under basic conditions to thiolates, providing a means of homopolymer attachment through vacant orbitals on the Gd3+ ions at the surface of the Gd MOF nanoparticles. Magnetic resonance imaging (MRI) confirmed the relaxivity rates of these novel polymer modified structures were easily tuned by changes in the molecular weight and chemical structures of the polymers. When a hydrophilic polymer was used for modification of the Gd MOF nanoparticles, an increase in molecular weight of the polymer provided a respective increase in the longitudinal relaxivity. These relaxivity values were significantly higher than both the unmodified Gd MOF nanoparticles and the clinically employed contrast agents, Magnevist and Multihance, which confirmed the construct's ability to be utilized as a positive contrast nanoparticle agent in MRI. Further characterization confirmed that increased hydrophobicity of the polymer coating on the Gd MOF nanoparticles yielded minimal changes in the longitudinal relaxivity properties but large increases in the transverse relaxivity properties in the MRI.
Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado 80401, USA.
Misty D
MD
Rowe
Chia-Chih
CC
Chang
Douglas H
DH
Thamm
Susan L
SL
Kraft
Joseph F
JF
Harmon
Andrew P
AP
Vogt
Brent S
BS
Sumerlin
Stephen G
SG
Boyes
D003287:Contrast Media / Q000138:chemical synthesis* / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties
D003287:Contrast Media; D011108:Polymers; D005682:Gadolinium