Validity of chromium-51 labelling of human erythrocytes as an assay for their survival after photodynamic therapy in vitro for blood sterilization.

Labelling of human erythrocytes with 51CrO42- is used as an assay for survival of red blood cells (RBC) in the circulation. To ascertain whether the assay is valid for RBC treated with sulfonated aluminium phthalocyanine and red light, a procedure designed for viral deactivation in RBC concentrates, we followed release of 51Cr and haemolysis after photosensitization. The results shows that 51Cr release does not occur until about 3 h prior to haemolysis. The absence of 51Cr loss from cells not committed to lysis indicates that the label technique is valid for determination of survival photosensitized RBC in the circulation.