Physiological effects of pathogen reduction of red blood cell products using antimicrobial blue light

Microbial contamination-associated transfusion-related sepsis though rare, is a significant issue in transfusion medicine. A number of current pathogen reduction technologies utilise ultraviolet or visible light with additional photosensitisers, but have limitations in the treatment of red cell products due to their opacity and sensitivity. Recent advancements have demonstrated the antimicrobial effects of 405-nm blue light for the decontamination of ex vivo animal and human plasma. Lethal oxidative damage occurs through the photo-excitation of endogenous microbial porphyrins at 405-nm, therefore eliminating the need for additional photosensitisers. This research investigated the antimicrobial and physiological effects of 405-nm light on red cell products. Ovine red cell suspensions, seeded with Staphylococcus aureus, were exposed to varying irradiances (1–100 mWcm-2) and doses (21.6-2160 Jcm-2) of 405-nm light to determine germicidal efficiency. Investigation into the effects of the 405-nm light on red cells was also determined through microscopy and hemolysis detection, with further investigation into the potential oxidising effects on hemoglobin through ELISA detection. Results demonstrated successful inactivation of low-level ( < 103 CFUml-1) bacterial contamination in red cell suspensions by 405-nm light treatment, with reduced germicidal potential found upon use of increasing red cell densities. Physiological analysis demonstrated that compatibility with red cell treatment is dependant on the treatment parameters (intensity, treatment time). Low-level illumination showed potential for compatiblity, however, high doses induced varying degrees of hemolysis, Met-hemoglobin formation and reduced viability. Further research is required to fully evaluate the potential of blue light based pathogen reduction in red blood cell products.