It is known that multiple cationic charges are required to produce broad-spectrum antimicrobial photosensitizers (PS) for photodynamic inactivation (aPDI) or photodynamic therapy of bacteria and fungi. In the present study we describe the synthesis and aPDI testing of a set of derivatives prepared from the parent pheophytin molecule with different numbers of attached side arms (1–3) each consisting of five quaternized cationic groups (pentacationic), producing the corresponding [Zn²⁺]pheophorbide-a-N(C₂N⁺C₁C₃)₅ (Zn-Phe-N₅⁺, 5 charges), [Zn²⁺]chlorin e₆-[N(C₂N⁺C₁C₃)₅]₂ (Zn-Chl-N₁₀⁺, 10 charges) and [Zn²⁺]mesochlorin e₆-[N(C₂N⁺C₁C₃)₅]₃ (Zn-mChl-N₁₅⁺, 15 charges). Moreover, a conjugate between Zn-Phe-N₅⁺ and the antibiotic vancomycin called Van-[Zn²⁺]-m-pheophorbide-N(C₂N⁺C₁C₃)₅ (Van-Zn-mPhe-N₅⁺) was also prepared. The aPDI activities of all compounds were based on Type-II photochemistry (¹O₂ generation). We tested these compounds against Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Escherichia coli, and the fungal yeast Candida albicans. All three compounds were highly active against MRSA, giving eradication (≥6 logs of killing) with <1.0 μM and 10 J cm⁻² of 415 nm light. The order of activity was Zn-Phe-N₅⁺ > Zn-Chl-N₁₀⁺ > Zn-mChl-N₁₅⁺. In the case of E coli the activity was much lower (eradication was only possible with 50 μM Zn-mChl-N₁₅⁺ and 20 J cm⁻²). The order of activity was the reverse of that found with MRSA (Zn-mChl-N₁₅⁺ > Zn-Chl-N₁₀⁺ > Zn-Phe-N₅⁺). Activity against C. albicans was similar to E. coli with Zn-mChl-N₁₅⁺ giving eradication. The activity of Van-Zn-mPhe-N₅⁺ was generally lower than that of Zn-Phe-N₅⁺ (except for E. coli). Red (660 nm) light was also effective as might be expected from the absorption spectra. An initial finding that Van-Zn-mPhe-N₅⁺ might have higher activity against vancomycin resistant Enterococcus fecium (VRE) strains (compared to vancomycin sensitive strains) was disproved when it was found that VRE strains were also more sensitive to aPDI with Zn-Phe-N₅⁺. The minimum inhibitory concentrations of Van-Zn-mPhe-N₅⁺ were higher than those of Van alone, showing that the antibiotic properties of the Van moiety were lessened in the conjugate. In conclusion, Zn-Phe-N₅⁺ is a highly active PS against Gram-positive species and deserves further testing. Increasing the number of cationic charges increased aPDI efficacy on C. albicans and Gram-negative E. coli.

中文翻译：

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用于抗菌光动力灭活的二氢卟酚衍生物的渐进式阳离子功能化及相关万古霉素缀合物

众所周知，需要多个阳离子电荷来产生广谱抗菌光敏剂（PS），用于细菌和真菌的光动力灭活（aPDI）或光动力治疗。在本研究中，我们描述了由母体脱镁叶绿素分子制备的一组衍生物的合成和 aPDI 测试，这些衍生物具有不同数量的附加侧臂 (1-3)，每个侧臂由五个季铵化阳离子基团（五阳离子）组成，产生相应的 [Zn ²⁺ ]脱镁叶绿酸- a -N(C ₂ N ⁺ C ₁ C ₃ ) ₅ (Zn-Phe-N ₅ ⁺ , 5 个电荷)，[Zn ²⁺ ]氯啉 e ₆ -[N(C ₂ N ⁺ C _{1 )} C ₃ ) ₅ ] ₂ (Zn-Chl-N ₁₀ ⁺ , 10 个电荷) 和 [Zn ²⁺ ]中二氯精 e ₆ -[N(C ₂ N ⁺ C ₁ C ₃ ) ₅ ] ₃ (Zn- m Chl-N ₁₅ ⁺，15次收费）。_{此外，Zn-Phe-N 5} ⁺和抗生素万古霉素之间的缀合物称为 Van-[Zn ²⁺ ]- m -脱镁叶绿酸-N(C ₂ N ⁺ C ₁ C ₃ ) ₅ (Van-Zn- m Phe-N _{5+ ）也准备}^好了。所有化合物的 aPDI 活性均基于 II 型光化学（¹ O ₂生成）。我们针对革兰氏阳性耐甲氧西林金黄色葡萄球菌(MRSA)、革兰氏阴性大肠杆菌和真菌酵母白色念珠菌进行了测试。^{所有三种化合物均对 MRSA 具有高度活性，用 <1.0 μM 和 10 J cm -2}的 415 nm 光即可根除（≥6 个杀死对数）。活性顺序为Zn-Phe-N ₅ ⁺ > Zn-Chl-N ₁₀ ⁺ > Zn- m Chl-N ₁₅ ⁺。就大肠杆菌而言，活性要低得多（只有使用 50 μM Zn- m Chl-N ₁₅ ⁺和 20 J cm ^-2才能根除）。活性顺序与 MRSA (Zn- m Chl-N ₁₅ ⁺> Zn-Chl-N ₁₀ ⁺ > Zn-Phe-N ₅ ⁺ )。Zn- m Chl-N ₁₅ ⁺对白色念珠菌的活性与大肠杆菌相似，可根除。Van-Zn- m Phe-N ₅ ⁺的活性普遍低于Zn-Phe-N ₅ ⁺ (大肠杆菌除外)。正如吸收光谱所预期的那样，红光（660 nm）也有效。最初发现 Van-Zn- m Phe-N ₅ ⁺可能对万古霉素耐药粪肠球菌(VRE) 菌株（与万古霉素敏感菌株相比）具有更高的活性，但当发现 VRE 菌株对 aPDI 也更敏感时，这一发现被推翻了。 Zn-Phe-N ₅ ⁺。Van-Zn- m Phe-N ₅ ⁺的最低抑制浓度高于单独的 Van，表明缀合物中 Van 部分的抗生素特性减弱。总之，Zn-Phe-N ₅ ⁺是一种针对革兰氏阳性菌的高活性 PS，值得进一步测试。增加阳离子电荷的数量可提高 aPDI 对白色念珠菌和革兰氏阴性大肠杆菌的功效。