Photochemical decontamination of red cell concentrates with the silicon phthalocyanine Pc 4 and red light

Virus inactivation in red blood cell concentrates (RBCC) is being studied i n order to increase the safety of the blood supply. For this purpose sue ha ve been studying the silicon phthalocyanine (Pc 4), a photosensitizer activ ated with red light. Two approaches were used to achieve enhanced selectivi ty of Pc 4 for virus inactivation. One was formulation of Pc 4 in liposomes that reduce its binding to red cells. The other was the use of a light emi tting diode (LED) array emitting at 700 nm. Vesicular stomatitis virus (VSV ) infectivity served as an endpoint for virus kill in heated RBCC. Red cell hemolysis and circulatory survival in rabbits served as measures for red c ell damage. Treatment of small aliquots of human RBCC with 2 mu M Pc 4 in l iposomes and 10 J/cm(2) of 700 nm LED light in the presence of the quencher s of reactive oxygen species glutathione and trolox resulted in 6 log(10) i nactivation of VSV. Under these conditions hemolysis of treated red cells s tored at 4 degrees C for 21 days was only slightly above that of control ce lls. Rabbit RBCC similarly treated circulated with a half life of 7.5 days compared with 10.5 days of control. It is concluded that Pc 4 used as descr ibed here may be useful for viral decontamination of RBCC, pending toxicolo gical and clinical studies. (C) 1999 Society of Photo-Optical Instrumentati on Engineers. [S1083-3668(99)00503-2].