Cheng Zhiliang, Tsourkas Andrew
Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
Sci Rep. 2014 Nov 7;4:6958. doi: 10.1038/srep06958.
To date, numerous analytical methods have been developed to monitor phospholipase A2 (PLA2) activity. However, many of these methods require the use of unnatural PLA2 substrates that may alter enzyme kinetics, and probes that cannot be extended to applications in more complex environments. It would be desirable to develop a versatile assay that monitors PLA2 activity based on interactions with natural phospholipids in complex biological samples. Here, we developed an activatable T1 magnetic resonance (MR) imaging contrast agent to monitor PLA2 activity. Specifically, the clinically approved gadolinium (Gd)-based MR contrast agent, gadoteridol, was encapsulated within nanometer-sized phospholipid liposomes. The encapsulated Gd exhibited a low T1-weighted signal, due to low membrane permeability. However, when the phospholipids within the liposomal membrane were hydrolyzed by PLA2, encapsulated Gd was released into bulk solution, resulting in a measureable change in the T1-relaxation time. These activatable MR contrast agents can potentially be used as nanosensors for monitoring of PLA2 activity in biological samples with minimal sample preparation.
迄今为止，已开发出多种分析方法来监测磷脂酶A2（PLA2）的活性。然而，这些方法中的许多都需要使用可能会改变酶动力学的非天然PLA2底物，以及无法扩展到更复杂环境应用的探针。开发一种基于与复杂生物样品中的天然磷脂相互作用来监测PLA2活性的通用检测方法将是很有必要的。在此，我们开发了一种可激活的T1磁共振（MR）成像造影剂来监测PLA2活性。具体而言，将临床批准的基于钆（Gd）的MR造影剂钆特醇包裹在纳米级磷脂脂质体中。由于膜通透性低，包裹的Gd呈现出低T1加权信号。然而，当脂质体膜内的磷脂被PLA2水解时，包裹的Gd被释放到本体溶液中，导致T1弛豫时间发生可测量的变化。这些可激活的MR造影剂有可能用作纳米传感器，以在最少样品制备的情况下监测生物样品中的PLA2活性。
