EFFECT OF MAGNETITE PARTICLES ON PHOTOINDUCED AND NONPHOTOINDUCED FREE-RADICAL PROCESSES IN HUMAN ERYTHROCYTES

Magnetite (Fe3O4) encapsulated in polystyrene microspheres dramaticall y decreased the time for 50% hemolysis (t(1/2)) of human erythrocytes irradiated (lambda > 300 mm) in the presence of ketoprofen (0.1 mM). T he magnetic microspheres were present at a very low concentration (0.0 02%) such that on average there was only one particle per four erythro cytes. No such effect was seen when nonmagnetic microspheres were empl oyed or when the equivalent concentration of soluble iron (FeCl3) was present. A decrease in t(1/2) was also observed when the magnetic micr ospheres were added after UVA/ketoprofen treatment or when they were p resent during hemolysis initiated by thermolysis of 2,2'-azobis(2-amid inopropane). These findings may be attributed to an increase in the me mbrane concentration of lipid radicals as a result of a magnetic field -induced increase in radicals escaping from triplet radical pairs.