Light‐based methods for whole blood bacterial inactivation enabled by a recirculating flow system

Abstract

Light of certain wavelengths can be used to inactivate pathogens. Whole blood is opaque; thus, the penetration of light is reduced. Here, we overcame this limitation using a thin transparent tube that is illuminated from all angles. Three light-based techniques were evaluated: photodynamic therapy (PDT) using a 660-nm light and antibody-photosensitizer conjugates, ultraviolet, and violet light. We observed a reduction of 55-71% of Staphylococcus aureus after 5 h of exposure (starting concentration 10 CFU mL ) and an 88-97% reduction in methicillin-resistant Staphylococcus aureus (MRSA) (starting 10 CFU mL ). An 83-92% decrease for S. aureus and 98-99.9% decrease for MRSA were observed when combined with an immunocapture approach. Complete blood count with differential analysis did not reveal any significant changes in the blood cell numbers. Genotoxicity studies showed that violet and ultraviolet did not induce any significant level of single strand breaks and alkali labile sites in the peripheral blood mononuclear cells (PBMC). In contrast, ultraviolet did induce a very low level of cyclobutane pyrimidine dimers, a UV damage indicator. PDT generated a significant level of single strand breaks and 8-oxoGua in these cells. The approaches showed promise for whole blood pathogen inactivation with minimal collateral damage to PBMC.

Design of Photosensitizing Agents for Targeted Antimicrobial Photodynamic Therapy

“…With this nano-platform, the authors claimed that the delivery of PS per binding event was 45 times higher than in the case of a PS-IgG immunoconjugate. A Ce6 immunoconjugate was also used for whole blood bacterial inactivation by Kim et al [ 172 ]. The red-absorbing PS was conjugated to a polyclonal antibody to S. aureus and to a penicillin-binding protein 2a monoclonal antibody for MRSA treatment.…”

Anti-Viral Photodynamic Inactivation of T4-like Bacteriophage as a Mammalian Virus Model in Blood

“…The T4-like phage inactivation with MB reached the detection limit of the method (reduction of 8 log 10 PFU/mL) after 30 min of irradiation in PBS ( Figure 4 d) and did not go beyond 3 log 10 PFU/mL of T4-like phage inactivation in plasma even after 270 min of irradiation ( Figure 5 d). Although the MB efficiency in the inactivation of microorganisms is highly dependent on the pH of the solution, PBS (pH 7.4) and plasma (pH 7.35 to 7.45) [ 53 ] have a similar pH, which indicates that other factors can be responsible for the high difference of aPDT’s effectiveness between PBS and plasma. The high organic content of plasma can explain the significantly lower T4-like phage inactivation with MB in plasma but also the MB photobleaching due to the high irradiance used (150 mW·cm −2 ) in the photoinactivation plasma assays.…”

“…Given this fact, the effectiveness of the PSs can be affected and consequently reduced. Furthermore, haemoglobin absorbs light comprising a large fraction of the visible light, and this can also contribute to reducing significantly the number of photons available to be absorbed by the PS and, consequently, reduce the PS efficacy in whole blood [ 53 ].…”

Editorial: Photodynamic Therapy as an Important Tool for Biological Breakthroughs—Photoactive Photosensitizers Applied from Cancer to Microbial Targets

“…Besides this, it is important to highlight that antimicrobial photodynamic therapy (aPDT) has been also explored as an innovative therapeutic approach because it can be used to inactivate a variety of microbial forms (e.g., bacteria [ 6 , 7 , 8 ], fungi [ 9 , 10 , 11 ], and viruses [ 12 , 13 , 14 ]) without causing significant damage to host tissues and without the development of resistance to the photosensitization process [ 15 ].…”