Metabolomics evaluation of the photochemical impact of violet-blue light (405 nm) on ex vivo platelet concentrates

Introduction
Microbicidal violet-blue light in the visible spectrum (405 nm) has been under evaluation for pathogen inactivation in ex vivo human plasma and platelets (PLTs) stored in plasma, and results to date have demonstrated that several blood-borne infectious disease-causing pathogens can be successfully reduced to significantly low levels in the light-treated plasma and PLTs.
Method
Towards understanding whether the microbicidal 405 nm light is safe for the treatment of blood components for pathogen inactivation, LC/MS-based metabolomics analyses were performed to evaluate the overall impact of 405 nm violet-blue light treatment on ex vivo PLT concentrates suspended in plasma and on plasma itself, and to identify metabolome changes in PLTs and plasma.
Results
The metabolomics data identified that platelet activating factors (PAFs), agonists and prostaglandins which can influence PLT basic functions such as integrity, activation, and aggregation potential were unaltered, suggesting that 405 nm light illumination is safer with regards to PLT basic functions. Distinct increases in hydroxyl fatty acids and aldehydes as well as decreases in antioxidant metabolites indicated that reactive oxygen species (ROS) were generated at high levels as early as 1h 405 nm light exposure. Distinctly changed endogenous photosensitizer metabolites as early as 1 h light exposure provides good evidence why 405 nm light is an effective microbicidal light through ROS mechanism and needs no external additive photosensitizers for this action.