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Tackling Sepsis after transfusions

UV-LED at 265 nm can potentially disinfect human platelet concentrates

Hayashi et al., 2021

Platelets are essential for stopping bleeding under low or high flow rates through surface molecules, including glycoproteins and released molecules in their granules. One way to stop bleeding in thrombocytopenic patients (with fewer platelets) is through platelet concentrates (PCs) transfusion. PCs can also prevent thrombocytopenia in patients receiving chemotherapy.

Most laboratories store PCs at room temperature (20-24˚C) under continuous agitation. But these storage conditions often allow bacterial contamination. Cold can prolong storage duration. However, cold-stored platelets survive for a shorter time after transfusion. Because of that, the shelf-life of PC products is relatively short, between 3 to 5 days.

Thus, it’s critical to find strategies to prevent PCs contamination and avoid sepsis after transfusion. The most widespread are culture-based detection of bacteria and pathogen inactivation procedures. Culture-based bacteria inactivation is highly sensitive, but it’s not perfect since bacteria grow during storage even with a low count. Pathogen inactivation techniques typically use UVA, UVB, or UVC, which can affect platelets in different ways.

Thus, researchers at the Japanese Red Cross Kinki Block Blood Centre, Japan, investigated the application of UV-LED at 265 nm as a novel disinfection method for platelet transfusion safety.

Study Overview

Platelet concentrates

The researchers obtained the PCs from healthy volunteers’ blood. They kept it at 22˚C with agitation before use.

Bacterial inoculation

The investigators cultured bacteria (E.coli, S.aureus, and B cereus) and suspended them in a saline solution, diluted to a predetermined bacterial concentration. After that, they spiked an aliquot of the suspension to 10 mL of PC.

UV-LED irradiation

Next, the researchers placed approximately 2,750µL of the PC-bacteria mixture in a petri dish to obtain a sample depth of 5mm. Then, they irradiated it with a UV-LED setup containing 8 UV-LED units of 3.5 mm square with a peak emission wavelength of 265 nm, a heat sink, and a cooling fan (Figure 1A and 1B). The incident irradiance at the surface of the mixture was 1.05 mW/cm2.

Fig 1. from Hayashi et al., 2021: UV-LED irradiation setup. (a) Samples were placed in a siliconized quartz glass dish (28-mm inner diameter) with a stir bar. Eight UV-LED units (265 nm) were placed on the board face down for irradiation; the distance between the UV-LED and the sample surface before sampling was 17.7 mm. (b) The emission spectrum of the UV-LED used in this study.

The investigators removed 100 uL samples from the dish every 5 or 10 minutes. These samples allowed them to measure platelet counts, glycoprotein surface expression., agonist-induced platelet aggregation, and platelet adherence and aggregation under flow conditions.

Platelet aggregation and adherence under flow conditions

For this experiment, the researchers loaded 50μL