RESEARCH ARTICLE

Photodynamic inactivation of Staphylococcus aureus in plasma using photogem: optimization and mechanistic insights    

Ananya Tewari, Jennifer Machado Soares, Vanderlei Bagnato

2026, 19(1): 3.https://doi.org/10.2738/foe.2026.0003

Abstract

Bacterial contamination of blood plasma, particularly by pathogens such as Staphylococcus aureus (S. aureus), including antibiotic resistant strains (e.g., MRSA), remains a critical challenge in transfusion medicine. Current pathogen reduction technologies face tradeoffs between microbial safety and plasma integrity, often degrading coagulation factors or requiring complex protocols. This study demonstrates a novel photodynamic inactivation (PDI) strategy using the photosensitizer Photogem® activated by 630 nm red light to achieve effective plasma decontamination while preserving functionality. Through systematic optimization of photosensitizer concentration (25–50 μg/mL) and light doses (15–60 J/cm2), we achieved a 3-log CFU/mL reduction of S. aureus in artificial plasma at 50 μg/mL with 60 J/cm2 irradiation, matching FDA sterilization thresholds for blood products. Crucially, plasma components enhanced Photogem® stability, reducing photobleaching rates by 1.5–2.5 × compared to PBS (decay constants: 0.025–0.07 min−1 vs. 0.045–0.1 min−1) through protein mediated molecular interactions. Fractionated light dosing with intermittent oxygenation overcame oxygen diffusion limitations, improving bacterial inactivation by 1-log in plasma. Fluorescence microscopy revealed 2 × greater photosensitizer retention in plasma versus PBS, attributed to albumin binding and porphyrin protein stabilization. This work establishes PDI as a clinically viable alternative to UV-C and solvent-detergent methods, balancing antimicrobial efficacy with plasma protein preservation. Our findings provide foundational data for developing closed system PDI devices to enhance blood product safety in transfusion workflows.

Ananya Tewari, Jennifer Machado Soares, Vanderlei Bagnato. Photodynamic inactivation of Staphylococcus aureus in plasma using photogem: optimization and mechanistic insights. Front. Optoelectron., 2026, 19(1): 3 https://doi.org/10.2738/foe.2026.0003

研究背景

血液制品（尤其是血浆）的细菌污染，特别是金黄色葡萄球菌（包括耐甲氧西林菌株MRSA）的污染，是输血医学中的重大安全挑战。现有病原体减少技术。目前的病原体减少技术面临着微生物安全性和血浆完整性之间的权衡：UV-C会显著降解凝血因子（10%–23%）；溶剂/去污剂法对细菌无效；405 nm光照方案引入了程序复杂性。因此，亟需一种既能高效灭菌又能保留血浆功能的新技术。

主要内容

本研究探索了一种基于光敏剂Photogem®（血卟啉衍生物）和630 nm红光的光动力灭活（PDI）策略，用于血浆中金黄色葡萄球菌的消毒。通过系统优化光敏剂浓度和光剂量，在人工血浆中实现了99.9%（3-log）的细菌减少（50 μg/mL + 60 J/cm²），达到FDA对血液制品的灭菌标准。进一步的研究表明血浆组分通过蛋白结合增强了Photogem®的稳定性，与磷酸缓冲生理盐水（PBS）相比，光漂白速率降低1.5–2.5倍。此外，提出分次光照+间歇供氧方案以克服血浆高粘度的氧扩散限制。

创新点

l 系统优化了Photogem®在血浆中的PDI参数：确定了50 μg/mL + 60 J/cm²为临床可行的灭菌窗口，对金黄色葡萄球菌实现了3-log的细菌减少，并达到FDA标准。

l 揭示了血浆的双重作用：血浆蛋白一方面会清除ROS从而抑制PDI，另一方面通过与光敏剂结合，增强光敏剂的稳定性（减缓光漂白、延长活性）和微生物定位。

l 开发了分次光照+间歇氧合方案：针对血浆高粘度的氧扩散限制，采用10 min间隔的分次光照并补充氧气，使细菌灭活效果提升1-log，解决了连续光照时氧耗竭的问题。

结论

本研究证实，Photogem®介导的光动力灭活是一种有效、可临床转化的血浆消毒技术。通过优化光敏剂浓度（50 μg/mL）和采用分次光照+间歇氧合方案，可在保留血浆功能（凝血因子活性>90%）的前提下实现金黄色葡萄球菌99.9%的减少，满足FDA对血液制品的灭菌要求。研究表明，血浆的分子复杂性可作为优势而非局限性，血浆蛋白可以稳定Photogem®，延长其活性，同时减轻光漂白，这是对损害血浆完整性的传统方法的关键进步，为开发闭环式血浆消毒装置提供了理论和实验基础。

（以上文字包含AI生成内容，仅供参考；请以原文为准。）