Metalloporphyrin-based phosphorescent nanoprobes are being developed for two-photon microscopy of oxygen. In these molecular constructs, the generation of porphyrin triplet states following two-photon excitation is induced by the intramolecular Förster-type resonance energy transfer from a covalently attached 2P antenna. In the earlier developed prototypes, electron transfer between the antenna and the metalloporphyrin strongly interferred with the phosphorescence, reducing the sensitivity and the dynamic range of the sensors. By tuning the distances between the antenna and the core, and adjusting their redox potentials, the unwanted electron transfer could be prevented. An array of phosphorescent Pt porphyrins (energy transfer acceptors) and 2P dyes (energy transfer donors) was screened using dynamic quenching of phosphorescence, and the FRET-pair with the minimal ET rate was identified. This pair, consisting of Coumarin-343 and Pt meso-tetra-(4-alkoxyphenyl)porphyrin, was used to construct a probe in which the antenna fragments were linked to the termini of G3 poly(arylglycine) (AG) dendrimer with PtP core. The folded dendrimer formed an insulating layer between the porphyrin and the antenna, simultaneously controlling the rate of oxygen quenching (Stern-Volmer oxygen quenching constant). Modification of the dendrimer periphery with oligoethyleneglycol residues made the probe's signal insensitive to the presence of proteins and other macromolecular solutes.

中文翻译：

---

基于金属卟啉的树枝状纳米探针的设计用于氧气的双光子显微镜

基于金属卟啉的磷光纳米探针正在开发用于氧气的双光子显微镜。在这些分子结构中，双光子激发后卟啉三重态的产生是由共价连接的 2P 天线的分子内 Förster 型共振能量转移引起的。在早期开发的原型中，天线和金属卟啉之间的电子转移强烈干扰了磷光，降低了传感器的灵敏度和动态范围。通过调整天线和核心之间的距离，并调整它们的氧化还原电位，可以防止不需要的电子转移。使用磷光的动态猝灭筛选了一系列磷光 Pt 卟啉（能量转移受体）和 2P 染料（能量转移供体），并确定了具有最小 ET 率的 FRET 对。这对由 Coumarin-343 和 Pt meso-tetra-(4-alkoxyphenyl)porphyrin 组成，用于构建探针，其中天线片段连接到具有 PtP 核心的 G3 聚(芳基甘氨酸) (AG) 树枝状聚合物的末端. 折叠的树枝状大分子在卟啉和天线之间形成绝缘层，同时控制氧猝灭的速率（Stern-Volmer 氧猝灭常数）。用低聚乙二醇残基修饰树枝状大分子使探针的信号对蛋白质和其他大分子溶质的存在不敏感。用于构建探针，其中天线片段连接到具有 PtP 核心的 G3 聚（芳基甘氨酸）（AG）树枝状聚合物的末端。折叠的树枝状大分子在卟啉和天线之间形成绝缘层，同时控制氧猝灭的速率（Stern-Volmer 氧猝灭常数）。用低聚乙二醇残基修饰树枝状大分子使探针的信号对蛋白质和其他大分子溶质的存在不敏感。用于构建探针，其中天线片段连接到具有 PtP 核心的 G3 聚（芳基甘氨酸）（AG）树枝状聚合物的末端。折叠的树枝状大分子在卟啉和天线之间形成绝缘层，同时控制氧猝灭的速率（Stern-Volmer 氧猝灭常数）。用低聚乙二醇残基修饰树枝状大分子使探针的信号对蛋白质和其他大分子溶质的存在不敏感。