Cantelli Andrea, Piro Francesca, Pecchini Pietro, Di Giosia Matteo, Danielli Alberto, Calvaresi Matteo
Dipartimento di Chimica "Giacomo Ciamician", Alma Mater Studiorum - Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy.
Dipartimento di Farmacia e Biotecnologie, Alma Mater Studiorum - Università di Bologna, via Francesco Selmi 3, 40126 Bologna, Italy.
J Photochem Photobiol B. 2020 Mar 13;206:111852. doi: 10.1016/j.jphotobiol.2020.111852.
Photodynamic therapy (PDT) is considered a very promising therapeutic modality for antimicrobial therapy. Although several studies have demonstrated that Gram-positive bacteria are very sensitive to PDT, Gram-negative bacteria are more resistant to photodynamic action. This difference is due to a different cell wall structure. Gram-negative bacteria have an outer cell membrane containing lipopolysaccharides (LPS) that hinder the binding of photosensitizer molecules, protecting the bacterial cells from chemical attacks. Combination of the lipopolysaccharides-binding activity of Concanavalin A (ConA) with the photodynamic properties of Rose Bengal (RB) holds the potential of an innovative protein platform for targeted photodynamic therapy against Gram-negative bacteria. A ConA-RB bioconjugate was synthesized and characterized. Approximately 2.4 RB molecules were conjugated per ConA monomer. The conjugation of RB to ConA determines a decrease of the singlet oxygen generation and an increase of superoxide and peroxide production. The photokilling efficacy of the ConA-RB bioconjugate was demonstrated in a planktonic culture of E. coli. Irradiation with white light from a LED lamp produced a dose-dependent photokilling of bacteria. ConA-RB conjugates exhibited a consistent improvement over RB (up to 117-fold). The improved uptake of the photosensitizer explains the enhanced PDT effect accompanying increased membrane damages induced by the ConA-RB conjugate. The approach can be readily generalized (i) using different photo/sonosensitizers, (ii) to target other pathogens characterized by cell membranes containing lipopolysaccharides (LPS).
光动力疗法（PDT）被认为是一种非常有前景的抗菌治疗方式。尽管多项研究表明革兰氏阳性菌对PDT非常敏感，但革兰氏阴性菌对光动力作用更具抗性。这种差异归因于不同的细胞壁结构。革兰氏阴性菌具有一层含有脂多糖（LPS）的外细胞膜，该膜阻碍了光敏剂分子的结合，从而保护细菌细胞免受化学攻击。伴刀豆球蛋白A（ConA）的脂多糖结合活性与孟加拉玫瑰红（RB）的光动力特性相结合，有望成为一种针对革兰氏阴性菌的靶向光动力治疗的创新蛋白平台。合成并表征了一种ConA-RB生物共轭物。每个ConA单体大约共轭了2.4个RB分子。RB与ConA的共轭导致单线态氧生成减少，超氧化物和过氧化物生成增加。在大肠杆菌的浮游培养物中证明了ConA-RB生物共轭物的光杀伤效果。用LED灯发出的白光照射产生了剂量依赖性的细菌光杀伤作用。ConA-RB共轭物比RB表现出持续的改善（高达117倍）。光敏剂摄取的改善解释了ConA-RB共轭物诱导的膜损伤增加所伴随的增强的PDT效果。该方法可以很容易地推广：（i）使用不同的光/声敏剂，（ii）针对其他以含有脂多糖（LPS）的细胞膜为特征的病原体。
