A new proof-of-concept in bacterial reduction: antimicrobial action of violet-blue light (405 nm) in ex vivo stored plasma

Bacterial contamination of injectable stored biological fluids such as blood plasma and platelet concentrates preserved in plasma at room temperature is a major health-risk. Current pathogen-reduction technologies (PRT) rely on the use of chemicals and/or ultraviolet-light, which affects product quality and can be associated with adverse events in recipients. 405nm violet-blue light is antibacterial without the use of photosensitizers, and can be applied at levels safe for human exposure, making it of potential interest for decontamination of biological fluids such as plasma. As a pilot study to test whether 405nm light is capable of inactivating bacteria in biological fluids, rabbit and human plasma were seeded with bacteria and treated with a 405nm light emitting diode (LED) exposure system (patent pending). Inactivation was achieved in all tested samples, ranging from low volumes to pre-bagged plasma. 99.9% reduction of low density bacterial populations (≤103 CFUml-1), selected to represent typical ‘natural’ contamination levels, were achieved using doses of 144 Jcm-2. The penetrability of 405nm light, permitting decontamination of pre-bagged plasma, and the non-requirement for photosensitizing agents, provides a new proof-of-concept in bacterial reduction in biological fluids, especially injectable fluids relevant to transfusion medicine.