Highly Sensitive Detection of Caspase-3/7 Activity in Living Mice Using Enzyme-Responsive 19F MRI Nanoprobes
Highly Sensitive Detection of Caspase-3/7 Activity in Living Mice Using Enzyme-Responsive 19F MRI Nanoprobes
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DOI：
10.1021/acs.bioconjchem.8b00167
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发表时间：
2018-05-01
影响因子：
4.7
通讯作者：
Kikuchi, Kazuya
中科院分区：
文献类型：
--
作者：
Akazawa, Kazuki;Sugihara, Fuminori;Kikuchi, Kazuya
活体哺乳动物深层组织中酶活性的高灵敏度成像提供了有关其生物学功能和开发新药的有用信息;然而，这种成像具有挑战性。F-19磁共振成像（MRI）适用于无内源性背景信号的酶活性的非侵入性可视化。虽然已经开发了各种酶响应的F-19 MRI探针，但由于其灵敏度低，大多数不能用于体内成像。最近，我们开发了独特的纳米颗粒，称为火焰，由液体全氟化碳核心和坚固的二氧化硅外壳组成，并在体内展示了其出色的灵敏度。在这里，我们报告了一种高度功能化的纳米探针，FLAME-DEVD 2，具有OFF/ON F-19 MRI开关，用于基于顺磁弛豫增强效应检测caspase-3/7活性。为了提高caspase-3对肽的切割效率，我们设计了一种新的Gd 3+络合物缀合肽，DEVD X（X = 1，2），其是串联重复X次的底物肽序列，并证明DEVD 2显示出比DEVD 1更快的切割动力学。通过将这一新概念纳入信号激活策略，FLAME-DEVD 2显示出响应于半胱天冬酶-3活性的高F-19 MRI信号增强率。在静脉注射FLAME-DEVD 2和凋亡诱导剂后，通过F-19 MRI成功地成像了活小鼠脾脏中的caspase-3/7活性。该成像平台显示了在体内高灵敏度检测酶活性的巨大潜力。
Highly sensitive imaging of enzymatic activities in the deep tissues of living mammals provides useful information about their biological functions and for developing new drugs; however, such imaging is challenging. F-19 magnetic resonance imaging (MRI) is suitable for noninvasive visualization of enzymatic activities without endogenous background signals. Although various enzyme-responsive F-19 MRI probes have been developed, most cannot be used for in vivo imaging because of their low sensitivity. Recently, we developed unique nanoparticles, called FLAMES, that are composed of a liquid perfluorocarbon core and a robust silica shell, and demonstrated their outstanding sensitivity in vivo. Here, we report a highly functionalized nanoprobe, FLAME-DEVD 2, with an OFF/ON F-19 MRI switch for detecting caspase-3/7 activity based on the paramagnetic relaxation enhancement effect. To improve the cleavage efficiency of peptides by caspase-3, we designed a novel Gd3+ complex-conjugated peptide, DEVD X (X = 1, 2), which is a substrate peptide sequence tandemly repeated X times, and demonstrated that DEVD 2 showed faster cleavage kinetics than DEVD 1. By incorporating this novel concept into a signal activation strategy, FLAME-DEVD 2 showed a high F-19 MRI signal enhancement rate in response to caspase-3 activity. After intravenous injection of FLAME-DEVD 2 and an apoptosis-inducing reagent, caspase-3/7 activity in the spleen of a living mouse was successfully imaged by F-19 MRI. This imaging platform shows great potential for highly sensitive detection of enzymatic activities in vivo.