Visible violet-blue light for pathogen reduction of blood plasma: assessment of broad spectrum antibacterial efficacy and preliminary compatibility studies

Bacterial contamination of blood products is a major concern in transfusion medicine. Continued efforts to improve blood safety include the use of pathogen reduction technologies (PRTs), which for plasma includes solvent-detergent treatment, or the use of ultraviolet or visible light in combination with photosensitizers. Non-ionizing violet-blue light, in the region of 405nm, has recently demonstrated potential for in situ treatment of ex vivo stored plasma and platelet products, without the need for additional photosensitizers. This study investigates the broad spectrum antibacterial efficacy of 405 nm light for pathogen reduction of plasma samples. Human plasma was seeded with a range of bacteria implicated in transfusion transmitted infections: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae and Yersinia enterocolitica. The organisms were seeded at 102 , 105 and 107 CFU mL1 densities and exposed to a 405 nm light dose of 360 Jcm2 (1-hr at 100 mWcm^-2 ). Broad spectrum antibacterial efficacy was observed, with significant bacterial inactivation achieved for all species (P≤0.05). 98.9 − 100 % inactivation was achieved across all seeding densities for all organisms except E. coli, which achieved 95.1 − 100.0 % inactivation. Preliminary protein analysis, conducted using SDS-PAGE, assessed the compatibility of an effective antibacterial dose with plasma proteins. Protein stability tests provide the first evidence for the compatibility of 405 nm light for the decontamination of plasma, with no visible signs of protein degradation detected for doses ≤ 1.8 kJcm^-2 . Future studies are required to determine the treatment regime that provides the optimal balance of antibacterial efficacy and product stability.