Fillion Adam J, Bricco Alexander R, Lee Harvey D, Korenchan David, Farrar Christian T, Gilad Assaf A
Department of Chemical Engineering, Michigan State University, East Lansing, Michigan, USA.
Department of Biomedical Engineering, Michigan State University, East Lansing, Michigan, USA.
bioRxiv. 2023 Mar 8:2023.03.08.531737. doi: 10.1101/2023.03.08.531737.
Chemical Exchange Saturation Transfer (CEST) magnetic resonance imaging (MRI) has been identified as a novel alternative to classical diagnostic imaging. Over the last several decades, many studies have been conducted to determine possible CEST agents, such as endogenously expressed compounds or proteins, that can be utilized to produce contrast with minimally invasive procedures and reduced or non-existent levels of toxicity. In recent years there has been an increased interest in the generation of genetically engineered CEST contrast agents, typically based on existing proteins with CEST contrast or modified to produce CEST contrast. We have developed an method for the evolution of peptide sequences to optimize CEST contrast and showed that these peptides could be combined to create biosensors for CEST MRI. A single protein, superCESTide 2.0, was designed to be 198 amino acids. SuperCESTide 2.0 was expressed in and purified with size-exclusion chromatography. The magnetic transfer ratio asymmetry (MTR ) generated by superCESTide 2.0 was comparable to levels seen in previous CEST reporters, such as protamine sulfate (salmon protamine, SP), Poly-L-Lysine (PLL), and human protamine (hPRM1). This data shows that novel peptides with sequences optimized for CEST contrast that utilizes a more comprehensive range of amino acids can still produce contrast when assembled into protein units expressed in complex living environments.
化学交换饱和转移（CEST）磁共振成像（MRI）已被确认为传统诊断成像的一种新型替代方法。在过去几十年中，已经进行了许多研究以确定可能的CEST剂，例如内源性表达的化合物或蛋白质，它们可用于通过微创程序产生对比，并且毒性水平降低或不存在。近年来，人们对基因工程CEST造影剂的产生越来越感兴趣，这些造影剂通常基于具有CEST对比的现有蛋白质或经过修饰以产生CEST对比。我们已经开发了一种用于肽序列进化以优化CEST对比的方法，并表明这些肽可以组合以创建用于CEST MRI的生物传感器。一种单一蛋白质，即SuperCESTide 2.0，设计为含有198个氨基酸。SuperCESTide 2.0在[具体表达系统未给出]中表达，并用尺寸排阻色谱法纯化。SuperCESTide 2.0产生的磁转移率不对称性（MTR ）与先前的CEST报告分子（如硫酸鱼精蛋白（鲑鱼鱼精蛋白，SP）、聚-L-赖氨酸（PLL）和人鱼精蛋白（hPRM1））中观察到的水平相当。该数据表明，具有为CEST对比而优化的序列且利用更广泛氨基酸范围的新型肽，当组装成在复杂生活环境中表达的蛋白质单元时，仍可产生对比。
