Composition of the additive solution affects red blood cell integrity after photodynamic treatment

BACKGROUND AND OBJECTIVES: Photodynamic treatment is a promising technique for pathogen inactivation of red blood cell concentrates. For protocol optimization, the influence of the composition of the storage solution on the integrity of phototreated red cells was studied. MATERIALS AND METHODS: Red blood cells were resuspended in the storage solutions SAG-M or AS-3 to a haematocrit (Hct) of 30%. After addition of the photosensitizer, 1,9-dimethylmethylene blue (DMMB) (25 microm), the suspensions were illuminated with red light, and potassium leakage and delayed haemolysis were determined. In some experiments, the cells were washed after illumination and resuspended in modified storage solutions. RESULTS: Illumination of red cells in the presence of DMMB resulted in an immediate, light-dose-dependent increase in potassium leakage. The illumination conditions used induced no detectable haemolysis immediately after photodynamic treatment. Potassium leakage was higher when the illumination was performed in AS-3. In contrast, delayed haemolysis, measured after overnight storage, was considerably lower when cells were stored in AS-3. This protection was mainly a result of the presence of citrate in AS-3. In addition, other impermeant solutes protected against haemolysis. CONCLUSIONS: The additive solution strongly influences the integrity of red cells after photodynamic treatment. Whereas the solution in which the cells are illuminated has a small effect on red cell integrity, the main influence of the additive solution is during post-treatment storage. Red cell integrity is best maintained when illumination is performed in SAG-M followed by storage in AS-3. The presence of non-permeant solutes, such as citrate, in the solution used for storage, prevents haemolysis of the phototreated, cation-permeable cells by counterbalancing the osmotic activity of haemoglobin