In order to develop thin-walled superparamagnetic nanoparticle suspensions
as a contrast agent for magnetic resonance imaging, phosphorylcholine PC wa
s used to coat iron oxide cores of 5 nm. Weak stable positively charged sus
pensions can be obtained at concentration greater than 3 mmol.l(-1) (corres
ponding to about 3.2 molecules per nm(2)); while the addition of phosphoryl
glycerol PG decreases the electrophoretic mobility.
Raising the pH over 6 leads to flocculation: the binding of PC on iron oxid
es as a function of pH appears to be reversible. By Langmuir analysis, two
adsorption domains may be observed with a maximal density of 3.48 and 6.55
mol.nm(-2), interpreted as a multilayer formation. (C) 1999 Academic Press.