405-nm Light for Bacterial Reduction in Blood Plasma: Preliminary investigations into antimicrobial efficacy and plasma protein integrity

Pathogen reduction technologies (PRT) for blood products can reduce the incidence of transfusion-transmitted infection and associated wastage of blood products. Visible 405nm-light has been shown to inactivate bacteria in situ in bagged blood plasma without the addition of photo-sensitive chemicals. However, threshold levels for plasma protein compatibility and optimal bactericidal activity are currently unknown. This study investigates different treatment conditions and their suitability for safely inactivating bacteria in blood plasma.

Plasma seeded with Staphylococcus aureus (102–105CFU/ml) was exposed to 405nm-light at low and high irradiances (10, 100mW/cm2) with treatment times ranging between 0.2–7-hr (≤252 Jcm-2). SDS-PAGE was then used to assess the light effect in terms of antimicrobial treatment levels on plasma protein integrity.

High and low intensity treatment regimens achieved significant bacterial inactivation (P=<0.05) with doses of 252 Jcm-2 achieving ≥99.3% reduction. Results suggest that lower irradiances have greater germicidal efficiency, with use of 10mWcm-2 achieving up to 30% greater inactivation than equivalent doses using 100mWcm-2. SDS-PAGE analysis demonstrated no major detrimental impact on protein integrity with any of the treatment conditions investigated. Minimal changes in protein bands (≈28kDa) were observed relative to positive control samples after application of doses >144 Jcm-2.

The results of this study have highlighted the safety potential of 405nm-light treatment on blood plasma. Further research is required to determine the upper and lower threshold treatment levels and functionality of plasma proteins post-exposure for further development of this technology as a PRT tool for application in transfusion medicine.