BIOMEDICAL APPLICATIONS OF MAGHEMITE FERROFLUID

The use of cell-targeted ferrofluid in the characterization of modific ations of cell membranes is reviewed. Maghemite ferrofluid was synthes ized by the Massart method, complexed with dimercaptosuccinic acid (FF ). Cell targeting by FF was developed by coupling FF to various biolog ical effecters such as antibodies, lectins, etc, which enabled magneti c cell sorting. Modifications in erythrocyte membranes were studied us ing FF bound to recombinant human annexin V (AN;FF) which is very sens itive, compared to other Anx-based reagents, in the early detection of phosphatidylserine (PS) exposition on the outer leaflet of the plasma membrane. Thus PS exposition on mouse RBC was detected already after a 24-h storage at 4 degrees C and, transiently, 24 h after their infec tion by Plasmodium parasites, at which time the parasites are Still co nfined to the liver, thus leading to the recruitment of young RBC and the accumulation of a species, intermediate between reticulocytes and erythrocytes, and the actual RBC target of plasmodial invasion. AnxFF revealed PS exposition on RBC from sickle cell anemia patients, follow ing various inflammations and already after 20 days of human blood sto rage under blood bank conditions. Such a sensitive detection should be similar to that of macrophages which recognize exposed PS on cells an d bring about the latter's elimination from the circulation. AnxFF bin ding determination was combined with that of cell electrophoretic mobi lity, glycerol resistance and filterability to characterize RBC membra ne modifications in Alzheimer's disease patients which suggested a con tinuous damage and regeneration in RBC of these patients. A logistic a nalysis suggested that several three-parameter combinations could perm it diagnosis of Alzheimer's disease with up to 95% accuracy. THP1 cell s and macrophages, derived themselves by incubation with retinoic acid , were bound to FF and placed in a radio frequency alternating magneti c field. Magnetocytolysis was associated with FF attachment to the cel ls without damage to non-bound cells and without heating of the surrou nding solution ((C) Societe francaise de biochimie et biologie molecul aire / Elsevier, Paris).