Two-Photon Ratiometric Fluorescent Mapping of Intracellular Transport Pathways of pH-Responsive Block Copolymer Micellar Nanocarriers
Two-Photon Ratiometric Fluorescent Mapping of Intracellular Transport Pathways of pH-Responsive Block Copolymer Micellar Nanocarriers
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pH 响应嵌段共聚物胶束纳米载体细胞内运输途径的双光子比率荧光图谱
DOI：
10.1002/adhm.201200436
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发表时间：
2013-12-01
影响因子：
10
通讯作者：
Liu, Shiyong
中科院分区：
文献类型：
--
作者：
Liu, Tao;Hu, Jinming;Liu, Shiyong
刺激响应性嵌段共聚物组件（例如胶束和囊泡）作为药物和基因递送纳米载体越来越受欢迎。 [1]响应生物相关环境（例如 pH、酶和氧化还原/氧化电位）而触发有效负载释放，可以提高病理部位的药物生物利用度，特别是在微酸性肿瘤细胞外基质内或细胞摄取时。 [2]特别是，表现出 pH 驱动崩解特征的响应性嵌段共聚物纳米载体与内吞囊泡运输过程中的酸性细胞器（例如内体和溶酶体）密切相关。 [3]人们普遍接受但尚未明确证明，具有适当 p Ka 的 pH 响应性胶束可能会促进内体逃逸和药物释放，这是由于与质子化触发的胶束到单聚体转变相关的渗透膨胀。 [3, 4] 因此，响应性胶束纳米载体经历的细胞内 pH 梯度的时空定量可以进一步阐明内吞转运途径和亚细胞分布。这将有助于优化生物响应药物纳米载体和 pH 可裂解聚合物-药物缀合物的设计。[3c, 5] 荧光聚合物和聚合物组件可以实现细胞动力学和过程的非侵入性实时光学成像。此前，荧光团标记的聚合物胶束、[6] 纳米颗粒 [7] 和单聚体链 [8] 已被用来探测细胞内 pH 梯度或组织 pH 异常，基于单个发射带 [6, 7f, 8a–d] 的 pH 引起的强度变化或两个发射带的比率测定。[7a–e, 8e–h] 请注意，后一种设计通常涉及具有两个反向变化的发射带的荧光共振能量转移原理。 [7a, b, 8e–g] 或将 pH 敏感染料与参考染料组合。[7c–e, 8h] 至于具有嵌段共聚物胶束的 pH 传感支架，Gao 及其同事 [6] 最近报道了用不同斯托克斯位移的荧光团锚定的含聚（叔胺甲基丙烯酸酯）的双亲水性嵌段共聚物（DHBC）制造基于单带强度的 pH 探针。它们在由于酸性细胞器内胶束到单聚体的转变而导致胶束状态和发射开启。 [6]受这项工作的启发，我们设想直接从 pH 响应嵌段共聚物胶束构建自校准和比例荧光 pH 探针可以提供与胶束纳米载体的囊泡运输途径相关的局部微环境的准确和定量信息。要实现这一目标，先决条件是在内吞相关范围 (pH 4.0–7.4) 内可以发生发射强度比的较大变化（即高灵敏度）。[7b, e] 请注意，对于仅涉及单一类型 pH 敏感染料（并与参考染料组合）的聚合物 pH 探针，灵敏且可靠的检测范围最多只能为 2 个 pH 单位。
Stimuli-responsive block copolymer assemblies such as micelles and vesicles have gained increasing popularity as drug and gene delivery nanovehicles.[1] Triggered payload release in response to biologically relevant milieu such as pH, enzymes, and redox/oxidation potentials can boost drug bioavailability at pathological sites, especially within the slightly acidic tumor extracellular matrix or upon cellular uptake.[2] In particular, responsive block copolymer nanocarriers exhibiting pH-actuated disintegration features are closely correlated with acidic cell organelles such as endosomes and lysosomes during endocytic vesicular trafficking.[3] It has been generally accepted but not definitively proven that pH-responsive micelles with appropriate p Ka might facilitate endosomal escape and drug release due to osmotic swelling associated with protonationtriggered micelle-to-unimer transition.[3, 4] Thus, the spatiotemporal quantification of intracellular pH gradients experienced by responsive micellar nanocarriers can further elucidate endocytic transport pathways and subcellular distributions. This will help optimize the design of bioresponsive drug nanocarriers and pH-cleavable polymer–drug conjugates.[3c, 5] Fluorescent polymers and polymeric assemblies can allow for the noninvasive and real-time optical imaging of cellular dynamics and processes. Previously, fluorophore-labeled polymeric micelles,[6] nanoparticles,[7] and unimer chains [8] have been utilized to probe intracellular pH gradients or tissue pH abnormalities, either based on pH-incurred intensity changes of a single emission band [6, 7f, 8a–d] or ratiometric assay of two emission bands.[7a–e, 8e–h] Note that the latter design typically involves the fluorescence resonance energy transfer principle with two inversely varying emission bands [7a, b, 8e–g] or combines a pH-sensitive dye with a reference dye.[7c–e, 8h] As for pH-sensing scaffold with block copolymer micelles, Gao and co-workers [6] recently reported the fabrication of singleband intensity-based pH probes from poly (tertiary amine methacrylate)-containing double-hydrophilic block copolymers (DHBCs) anchored with fluorophores of varying Stokes shift.They exhibit quenched fluorescence in the micellar state and emission turn-on due to micelle-to-unimer transition within acidic organelles.[6] Inspired by this work, we envisage that the construction of self-calibrating and ratiometric fluorescent pH probes directly from pH-responsive block copolymer micelles could provide accurate and quantitative information about local microenvironment associated with the vesicular trafficking pathway of micellar nanocarriers. To accomplish this, a prerequisite would be that large changes in emission intensity ratios (ie, high sensitivity) can occur over the endocytically relevant range (pH 4.0–7.4).[7b, e] Note that for polymeric pH probes only involving a single type of pH-sensitive dye (and in combination with a reference dye), the sensitive and reliable detection range can be only up to 2 pH units.