Here, we propose a zwitterionic near-infrared (NIR) fluorophore-tryptophan (Trp) conjugate with a cleavable linker as a minimal-sized versatile platform (MP) for the preparation of peptide ligand-based off-on type molecular probes. The zwitterionic NIR fluorophore in MP undergoes fluorescence quenching via a photoinduced electron transfer mechanism when in close proximity to tryptophan, and nonspecific binding with serum proteins is minimized by the zwitterionicity of the fluorophore. The linker can be cleaved inside cancer cells in response to tumor-associated stimuli. As a proof-of-concept experiment, ATTO655 was covalently linked with Trp via a diarginine linker to form an MP. A cyclic peptide consisting of Arg-Gly-Asp-d-Phe-Lys (cRGD) was used as a cancer-targeting ligand and was conjugated to the MP to form cRGD-MP. The NIR fluorescence of cRGD-MP could be selectively turned on inside the target cancer cells, thereby enabling specific fluorescence imaging of integrin αvβ3-overexpressing cancer cells in vitro and in vivo.

中文翻译：

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使用肽靶向配体进行近红外荧光成像的微型平台。

在这里，我们建议两性离子的近红外（NIR）荧光团-色氨酸（Trp）与可裂解的接头作为最小尺寸的通用平台（MP），用于制备基于肽配体的关闭型分子探针。MP中的两性离子NIR荧光团在靠近色氨酸时会通过光诱导的电子转移机制进行荧光猝灭，并且通过荧光团的两性离子化作用，与血清蛋白的非特异性结合得以最小化。响应于肿瘤相关刺激，接头可在癌细胞内裂解。作为概念验证实验，ATTO655通过精氨酸接头与Trp共价连接，形成MP。由Arg-Gly-Asp-d-Phe-Lys（cRGD）组成的环状肽用作靶向癌症的配体，并与MP偶联形成cRGD-MP。