Selective protection of RBCs against photodynamic damage by the band 3 ligand dipyridamole

BACKGROUND: All studied photosensitizers for virus inactivation impair RBCs . To reduce damage to the RBCs without affecting virucidal activity, select ive protection of the RBCs is necessary. The ability of the band 3 ligand, dipyridamole, to react with singlet oxygen and to increase the selectivity of photosterilization was investigated. STUDY DESIGN AND METHODS: Solutions of dipyridamole were illuminated in the presence of tetrasulfonated aluminum phthatocyanine (AIPcS(4)) and dimethy lmethylene blue (DMMB). Solutions of amino acids, RBCs, and vesicular stoma titis virus (VSV) in RBC suspensions were photodynamically treated in the p resence or absence of dipyridamole. RESULTS: illumination of a solution of dipyridamole in the presence of AIPc S(4) or DMMB resulted in changes in the optical spectrum of dipyridamole. T he photooxidation of dipyridamole was inhibited by azide and augmented by D 2O, which suggests the involvement of singlet oxygen. Photooxidation of ami no acids and photodamage to RBCs was strongly reduced in the presence of di pyridamole. In contrast, photoinactivation of VSV in RBC suspensions was on ly slightly affected by dipyridamole. CONCLUSION: Dipyridamole can improve the specificity of photodynamic steril ization of RBC concentrates, thereby increasing the practical applicability of this photodecontamination method.