Non-ionizing 405 nm Light as a Potential Bactericidal Technology for Platelet Safety: Evaluation of in vitro Bacterial Inactivation and in vivo Platelet Recovery in Severe Combined Immunodeficient Mice

Abstract

Bacterial contamination of ex vivo stored platelets is a cause of transfusion-transmitted infection. Violet-blue 405 nm light has recently demonstrated efficacy in reducing the bacterial burden in blood plasma, and its operational benefits such as non-ionizing nature, penetrability, and non-requirement for photosensitizing agents, provide a unique opportunity to develop this treatment for in situ treatment of ex vivo stored platelets as a tool for bacterial reduction. Sealed bags of platelet concentrates, seeded with low-level Staphylococcus aureus contamination, were 405 nm light-treated (3-10 mWcm −2 ) up to 8 h. Antimicrobial efficacy and dose efficiency was evaluated by quantification of the post-treatment surviving bacterial contamination levels. Platelets treated with 10 mWcm −2 for 8 h were further evaluated for survival and recovery in severe combined immunodeficient (SCID) mice. Significant inactivation of bacteria in platelet concentrates was achieved using all irradiance levels, with 99.6-100% inactivation achieved by 8 h (P < 0.05). Analysis of applied dose demonstrated that lower irradiance levels generally resulted in significant decontamination at lower doses: 180 Jcm −2 /10 mWcm −2 (P = 0.008) compared to 43.2 Jcm −2 /3 mWcm −2 (P = 0.002). Additionally, the recovery of light-treated platelets, compared to non-treated platelets, in the murine model showed no significant differences (P = >0.05). This report paves the way for further comprehensive studies to test 405 nm light treatment as a bactericidal technology for stored platelets.

Complete Inactivation of Blood Borne Pathogen Trypanosoma cruzi in Stored Human Platelet Concentrates and Plasma Treated With 405 nm Violet-Blue Light

“…In conclusion, we demonstrated that the blood borne pathogen T. cruzi can be effectively inactivated by over 9.0 log 10 in PL and in PCs using 405 nm light at a dose of 270 Jcm −2 (15 mWcm −2 for 5 h) and that under these light conditions, platelets retained acceptable metabolic indices and aggregation potential. All the experimental evidences that we have accumulated so far (16,17,26), including this report, together form the basis for generating a working hypothesis that 405 nm light treatment could evolve as a simple and gentler but effective PRT system for blood component safety from bacteria, viruses and parasites, provided in-depth studies are under taken in a timely fashion to further evaluate the system.…”

“…We have previously demonstrated that violet-blue light of 405 nm wavelength alone with no added photosensitizers is effective as a bacterial inactivator (16,26); since the light wavelength is in the visible spectra, it also served as a gentle treatment for stored platelets in terms of their survival and recovery as evaluated in a SCID mouse model, while providing safety from bacteria (16). In this system, photons at 405 nm excite endogenous porphyrins (circumventing the need for an external photosensitizer) within microbial cells to a higher energy state by energy transfer; subsequent transition of electrons from the porphyrin's excited state to the ground state is accompanied with the release of toxic reactive oxygen species, including singlet oxygen molecules, which cause damage to the microbial membranes, proteins and nucleic-acids resulting in pathogen inactivation (13,34,35).…”

“…In our previous studies we investigated bacterial inactivation rates under different exposure doses ranging from 36 to 288 J/cm 2 . PCs exposed to 10 mW/cm 2 light for 8 h (288 J/cm 2 ) and injected into SCID mice were found to sustain the same recovery as untreated PC samples (16). In this study, we have applied a higher irradiation of 15 mW/cm 2 light but for a shorter time, up to 5 h, equivalent to a reduced dose of 270 Jcm −2 .…”

“…In this study, we have applied a higher irradiation of 15 mW/cm 2 light but for a shorter time, up to 5 h, equivalent to a reduced dose of 270 Jcm −2 . Doses in this region were sufficient to inactivate ≥99% of tested bacteria and virus from human platelets and plasma (16).…”

“…In parallel, numerous studies have also demonstrated that 405 nm violet-blue light which is in the visible spectrum can effectively inactivate a wide range of pathogens including bacteria, spore-forming bacteria, fungi (13)(14)(15)(16) and some noroviruses in liquid medium as well as in human plasma (17). This 405 nm treatment for pathogen inactivation has added operational advantages of not requiring the addition of photosensitizers or extensive processing and requiring only direct exposure of the storage container (bag) that has the transfusion component (plasma or platelets suspended in plasma).…”