Sulfophthalocyanines for photodynamic inactivation of viruses in blood products: effect of structural modifications

Transmission of infectious disease through blood transfusions is well known. Ultraviolet irradiation, solvents, and detergents provide a means of sterilizing noncellular blood components. However, these harsh methods are not applicable to cellular blood products. Recently, attempts have been made to sterilize biological fluids using photodynamic treatment and phthalocyanine (Pc) dyes have been advanced as photosensitizers for this purpose. We have evaluated a series of water-soluble Pc, chelated with different central metal ions, substituted to different degrees with sulfonato and t-butyl groups, for their effectiveness to reduce virus infectivity in red blood cell suspensions. Vaccinia virus cytopathogenicity was determined by endpoint serial dilutions in the CV-1 cell line. Anti-viral activity increased with the central metal ion in the following: Ga(III) < Al(III) < Zn(II), and varied inversely with the degree of sulfonation. Furthermore, addition of a t-butyl group onto the trisulfonated dyes (PcS3[t-Bu]) resulted in a 5-40-fold increase in anti-viral potency, suggesting that amphiphilicity enhances the photodynamic activity of the dye. Strong anti-viral photosensitizing properties cannot be the sole selection criterion. Of equal importance is the preservation of blood component integrity. Accordingly, the photohemolytic activity of the dyes was evaluated using the rate of hemolysis as a parameter and a toxicity index was defined. Among the most active dyes, the AlPcS3(t-Bu) complex exhibited the most favorable anti-viral properties combined with a low toxicity index. Our results suggest that trisulfophthalocyanines, bearing an additional t-butyl group to enhance amphiphilicity, are particularly promising dyes for photodynamic blood sterilization.