【JACS】10cm 组织穿透！DNA 靶向声动力疗法攻克深部缺氧细菌感染
文章标题：DNA-Targeted Sonodynamic Activation Enhances Antibacterial Efficacy in Deep and Hypoxic Infections
通讯作者：Junrong Li、Ruiping Zhang、Yao Sun、Jong Seung Kim
文章概要
引言
深部细菌感染一直是临床难以根治的难题，其中铜绿假单胞菌引发的肺部感染尤为棘手，这类致病菌不仅极易产生抗生素耐药性，还能形成致密生物膜，躲避机体免疫与药物的攻击，造成感染反复迁延。目前应用较多的光动力疗法依靠活性氧实现杀菌，不易诱发耐药，但受限于光线的物理特性，组织穿透深度极浅，完全无法作用于肺部这类深部组织。声动力疗法以超声波作为激发源，拥有出色的组织穿透能力，弥补了光动力疗法的短板，不过现阶段主流声敏剂普遍存在活性偏低、缺乏靶向性的问题，再加上活性氧自身寿命短、扩散范围极小，进一步限制了治疗效果。细菌 DNA 裸露在细胞质中，没有核膜保护，是理想的抗菌作用靶点，但专门靶向细菌 DNA 的抗菌声敏剂一直十分匮乏。基于这一现状，研究团队选取已进入二期临床研究的钌基光敏剂TLD1433展开探索，尝试挖掘它全新的声动力活性，希望借助其分子特性实现细菌 DNA 靶向杀伤，同时改善感染病灶的缺氧微环境，构建一套全新的深部缺氧细菌感染治疗方案。
Figure 1. Schematic illustration of TLD1433 as DNA-targeting sonosensitizer for P. aeruginosa-induced pneumonia treatment.
主要实验及结论
研究团队首先完成了超声波作用参数的系统性优化，最终确定1 W cm⁻²、1 MHz为最优工作条件，在此基础上对比了 IR-780、原卟啉 IX、吲哚菁绿、Ru (bpy)₃Cl₂等多种商用及经典声敏剂，实验数据显示，TLD1433 经超声激发后产生活性氧的能力提升约 14.4 倍，远超过所有对照试剂，并且在接近生理环境的高含水体系中，它的声动力活性还能进一步增强。借助电子自旋共振、特异性荧光探针等多种检测手段，团队证实 TLD1433 在超声刺激下主要生成单线态氧，这也是其发挥抗菌作用的核心活性物质。除此之外，该分子还具备类酶催化功能，能够分解病灶内源性过氧化氢生成氧气，短短 500 秒内可使体系溶解氧含量提升约 16 mg L⁻¹，有效缓解生物膜内部的缺氧状态，而新增的氧气又能将单线态氧的生成效率再提升约 2.6 倍，形成良性的协同增效作用。组织仿体穿透实验直观证明，超声激活的 TLD1433 在10 cm 深度的模拟组织中依旧能保留 90% 的活性，远超激光激发的光动力疗法，同时该分子在血清、细菌培养液以及长时间超声照射下都能保持结构稳定，具备开展生物应用的扎实基础。
Figure 2. US-triggered ROS production by TLD1433. (a) ROS formation by TLD1433 under US treatment, monitored using DCFH as a fluorescent probe. (b) Heatmap representation of time-dependent changes in DCFH fluorescence intensity (λem = 525 nm), reflecting ROS generation by TLD1433 or representative commercial sonosensitizers under US treatment. (c) Fluorescence spectra of DCFH in the presence of TLD1433 in DMSO/H2O mixtures with different fractions of H2O under US treatment. (d) Dissolved oxygen levels measured after incubation with TLD1433 or Ru(bpy)3Cl2. (e) Kinetic analysis of DPBF consumption at 422 nm, expressed as −ln(A/_A_0), following the addition of TLD1433 at different H2O2 concentrations. (f) Detection of 1O2 using ESR spectroscopy. (g) Fluorescence imaging of ROS formation at different penetration depths in tissue-mimicking phantoms under US or 530 nm laser excitation. (h) Absorption spectra of TLD1433 after US irradiation of different time.
团队随后围绕TLD1433 的 DNA 靶向能力展开全面验证，紫外光谱、荧光光谱、等温滴定量热以及分子对接等实验结果表明，TLD1433 可以通过 π-π 堆积作用结合细菌 DNA，结合常数达到 8.68×10⁵ M⁻¹，结合后仅会造成 DNA 局部结构改变，不会破坏其整体构象。该分子对 DNA 展现出高度选择性，氨基酸、谷胱甘肽、各类无机离子等体内常见生物物质都不会与其发生明显相互作用，而对照试剂 Ru (bpy)₃Cl₂则几乎不具备 DNA 结合能力。体外抗菌实验以铜绿假单胞菌为主要研究对象，结果显示超声联合 TLD1433 的治疗方案杀菌效果显著优于传统钌配合物和临床抗生素环丙沙星，扫描电镜与透射电镜观察到细菌出现细胞膜破裂、胞质流失等典型损伤。转录组测序分析进一步揭示，该疗法会大幅下调细菌 DNA 复制、基因损伤修复、氧化应激防御以及细胞分裂相关基因的表达，从根源上阻断细菌的生存与增殖。针对临床危害极大的细菌生物膜，30 μM 的 TLD1433 联合超声可实现87% 的生物膜清除率，它能够渗透至生物膜多层结构内部，同步完成补氧与产生活性氧的过程，彻底破坏生物膜结构与内部菌体，团队还初步验证该策略对金黄色葡萄球菌也具备杀伤效果，说明其应用范围存在拓展空间。
Figure 3. DNA binding properties of TLD1433. UV–vis absorption (a) and fluorescence (b) spectra of TLD1433 with ctDNA. (c) Selectivity of TLD1433 toward DNA over other biologically relevant species including: 1. Blank; 2. GSH; 3. d-Val; 4. Gly; 5. l-Ile; 6. Na+; 7. K+; 8. Cl–; 9. ctDNA (n = 3 independent samples per group, data are presented as mean ± s.d.). (d) ITC analysis of the binding between TLD1433 and ctDNA. The raw heat flow as a function of time upon successive injections of TLD1433 into ctDNA solution (Upper panel). The corresponding integrated heat data plotted against the molar ratio of TLD1433 to ctDNA, together with the fitted binding isotherm (Lower panel). (e) Fluorescence spectra of TLD1433 with isolated bacterial DNA from P. aeruginosa. (f) DLS size distributions of isolated P. aeruginosa genomic DNA before and after incubation with TLD1433. (g) Molecular docking study depicting the space, where TLD1433 binds to DNA. (h) Molecular docking analysis of TLD1433 with DNA to show the distances (Å) between selected nonbonded interactions and the key interacting nucleotides.
Figure 4. In vitro evaluation of antibacterial activity against P. aeruginosa. (a) Relative survival rate of P. aeruginosa after different treatments (n = 3 independent biological replicates, data are presented as mean ± s.d.). G1: Ru(bpy)3Cl2; G2: Ru(bpy)3Cl2 plus US irradiation; G3: ciprofloxacin; G4: TLD1433; G5: TLD1433 plus US irradiation. Statistical significance was analyzed using two-tailed Student’s t test. (b) Zeta potential changes of P. aeruginosa after different treatments (n = 3 independent biological replicates, data are presented as mean ± s.d.). One-way ANOVA with Dunnett’s multiple comparisons test. (c) Confocal images of P. aeruginosa stained with DCFH-DA after different treatments (scale bar: 10 μm). (d) SEM and TEM images of P. aeruginosa after different treatments (scale bar for SEM: 0.5 μm; scale bar for TEM: 1 μm).
在细胞与分子实验的基础上，研究人员构建了铜绿假单胞菌肺炎小鼠模型，开展体内疗效与安全性评价。动物实验结果显示，接受 TLD1433 联合超声治疗的小鼠，肺部细菌载量相比空白组下降约6 个数量级，肺部肺泡结构基本恢复完好，肺泡渗出、炎性细胞浸润等肺炎典型病理症状得到明显缓解，血清中 IL-6、TNF-α 等促炎因子水平也显著降低。生存期统计数据显示，该治疗组小鼠最终实现100% 存活率，而空白对照组小鼠存活率仅为 25%。研究团队对小鼠心、肝、脾、肾等重要脏器进行病理切片、血常规和血清生化检测，确认治疗剂量下的 TLD1433 不会对机体造成明显毒副作用，生物相容性良好。为验证临床转化潜力，团队收集了铜绿假单胞菌感染患者的支气管肺泡灌洗液，在 10 cm 组织仿体模拟深部感染的条件下开展离体实验，最终发现这套声动力方案几乎可以完全清除临床样本中的致病菌，细菌染色结果也证实菌体细胞膜已被严重破坏，充分证明该疗法在临床深部缺氧肺部感染中拥有实际应用价值。
Figure 5. In vitro transcriptomics analysis. (a) Volcano plot of differentially expressed genes (DEGs) between the control group and the TLD1433 plus US treatment group (|log2fold change| ≥ 1 and adjusted P < 0.05). (b) PCA of the different groups. (c) Pearson correlation heatmap between the different samples. (d) KEGG enrichment analysis of DEGs after TLD1433 plus US treatment. (e) Hierarchical clustering heatmap of DEGs involved in genome maintenance, redox homeostasis, and cell proliferation.
Figure 6. In vitro assessment of antibiofilm efficacy and mechanistic studies against P. aeruginosa biofilms. (a) Representative images of biofilms visualized by crystal violet staining following the indicated treatments (scale bar: 200 μm). (b) Quantitative analysis of biofilm viability after different treatments (n = 3 biologically independent samples; data are presented as mean ± s.d.). G1: Ru(bpy)3Cl2; G2: Ru(bpy)3Cl2 plus US irradiation; G3: ciprofloxacin; G4: TLD1433; G5: TLD1433 plus US irradiation. Statistical significance was analyzed using two-tailed Student’s t test. Three-dimensional reconstructed fluorescence images of biofilms stained with RDPP (c) and DCFH-DA (d).
Figure 7. In vivo evaluation of sonotherapeutic efficacy in P. aeruginosa-infected pneumonia models. (a) Schematic illustration outlining the in vivo experimental workflow. (b) Diagram depicting the procedure used for bacterial quantification in infected lung tissues. (c) Representative agar plate images showing bacterial colonies recovered from lung tissues. (d) Quantitative analysis of bacterial burden in lung tissues following the indicated treatments (n = 5 biologically independent samples; data are presented as mean ± s.d.). Statistical significance was analyzed using two-tailed Student’s t test. (e) Representative H&E-stained lung sections collected at different time points after treatment (scale bar: 50 μm). Yellow arrows indicate alveolar exudation, and green circles highlight focal inflammatory lesions. (f) Cytokine levels of IL-6 in serum after different treatment groups at different time-points (n = 3 biologically independent samples). (g) Survival curves of mice with bacterial pneumonia after different treatment (n = 15 biologically independent mice per group). G1: PBS; G2: PBS plus US irradiation; G3: Ru(bpy)3Cl2; G4: Ru(bpy)3Cl2 plus US irradiation; G5: ciprofloxacin; G6: TLD1433; G7: TLD1433 plus US irradiation.
Figure 8. Ex vivo evaluation of the sonotherapeutic antibacterial efficacy in P. aeruginosa-positive patient-derived BALF samples. (a) Schematic illustration of the workflow of clinical samples. P. aeruginosa-positive BALF was collected from patients diagnosed with lung bacterial infection, followed by US irradiation, spread-plate culture for bacterial viability assessment and fluorescence staining. (b) Representative agar plate images showing bacterial colonies in BALF samples from five representative patients (P1–P5) after different treatments. (c) Quantitative analysis of bacterial survival ratios in 10 independent P. aeruginosa-positive patient-derived BALF samples (data are presented as mean ± s.d.). Statistical significance was analyzed using two-tailed Student’s t test. G1: PBS; G2: PBS + US; G3: Ru(bpy)3Cl2; G4: Ru(bpy)3Cl2 + US; G5: ciprofloxacin; G6: TLD1433; G7: TLD1433 + US. (d) Fluorescence images of SYTO 9-stained bacteria (scale bar: 10 μm).
总结及展望
这项研究创新性地将已步入临床阶段的钌基光敏剂TLD1433开发为 DNA 靶向型声敏剂，巧妙融合了细菌 DNA 靶向损伤、缺氧微环境调控、超声波深部激活三大核心优势，成功解决了传统光动力疗法穿透深度不足、常规声动力疗法靶向性差、感染部位缺氧制约疗效等多项行业痛点。整套治疗方案在分子、细胞、动物模型以及临床患者样本多个层面，都展现出优异的抗菌、抗生物膜能力，同时兼具可靠的生物安全性。该成果不仅为深部、缺氧型难治性细菌感染，尤其是耐药菌引发的肺部感染，提供了一种全新的非抗生素治疗思路，也为后续设计研发新一代靶向型声敏剂搭建了完整的理论与实验框架。未来研究可以在此基础上进一步优化分子结构，提升声敏剂的靶向效率与治疗性能，同时逐步推进大动物实验与临床试验探索，让这种新型声动力抗菌疗法早日落地临床，助力应对全球日益严峻的细菌抗生素耐药危机。