利用 RESCA 对 Affibody 分子进行氟-18 辐射标记的优化方法。

IF 4.4 Q1 CHEMISTRY, INORGANIC & NUCLEAR

EJNMMI Radiopharmacy and Chemistry Pub Date : 2024-10-26 DOI:10.1186/s41181-024-00304-9

Francesco Lechi, Jonas Eriksson, Luke R. Odell, Olivia Wegrzyniak, John Löfblom, Fredrik Y. Frejd, Bo Zhang, Olof Eriksson

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引用次数: 0

摘要

背景：近年来，Al[18F]F 作为正电子发射断层扫描（PET）放射性同位素的标记剂受到越来越多的关注，因为它可以利用化学螯合作用快速高效地标记氟-18。抑制络合剂（RESCA）作为螯合剂的引入也表明，基于螯合剂的放射性标记反应可以在温和的条件下进行，使放射性标记过程比大多数传统的放射性氟化方法更加简便。本研究的目的是以 Z09591 和 Z0185 这两种分别靶向 PDGFRβ 和 TNFα 的 Affibody 蛋白为模型化合物，建立以 RESCA 为络合剂对 Affibody 分子进行 Al[18F]F 标记的优化条件：在不同温度（恒温至 60 °C）和不同反应时间（12 至 60 分钟）下测试了 RESCA 结合物 Z09591 的 Al[18F]F 标记，然后对 RESCA-Z0185 实施了最佳条件。优化的合成方法是：将 1.5-2.5 GBq 回旋加速器产生的氟-18 捕获在 QMA 滤芯上，然后用生理盐水洗脱，与 12 nmol AlCl3 反应生成 Al[18F]F。将 NaOAc 溶液中相应的 RESCA 结合物 Affibody 分子（14 nmol）加入 Al[18F]F 溶液中，在 60 °C 下反应 12 分钟。混合物在 NAP5 尺寸排除柱上纯化，然后通过 HPLC 进行分析。整个过程耗时约 35 分钟，重复性很高，表明该方法高效可靠。纯化后的标记化合物保留了各自靶点的生物功能：我们提出了一种对 RESCA 结合物 Affibody 分子进行 Al[18F]F 标记的通用优化方法，该方法可广泛应用于这类基于多肽的成像剂。此外，在 37 ℃ 或更高温度下进行标记可提高放射化学产率。对相应示踪剂的体外和体内评估结果表明，这些示踪剂具有良好的结合能力和适度的脱氟，而脱氟通常被认为是RESCA共轭示踪剂的潜在缺点。

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Optimized method for fluorine-18 radiolabeling of Affibody molecules using RESCA

Background

In recent years, the interest in Al[¹⁸F]F as a labeling agent for Positron Emission Tomography (PET) radiotracers has risen, as it allows for fast and efficient fluorine-18 labeling by harnessing chelation chemistry. The introduction of Restrained Complexing Agent (RESCA) as a chelator has also shown that chelator-based radiolabeling reactions can be performed in mild conditions, making the radiolabeling process attractively more facile than most conventional radiofluorination methods. The aim of the study was to establish optimized conditions for Al[¹⁸F]F labeling of Affibody molecules using RESCA as a complexing agent, using Z₀₉₅₉₁ and Z₀₁₈₅, two Affibody proteins targeting PDGFRβ and TNFα, respectively, as model compounds.

Results

The Al[¹⁸F]F labeling of RESCA-conjugated Z₀₉₅₉₁ was tested at different temperatures (rt to 60 °C) and with varying reaction times (12 to 60 min), and optimal conditions were then implemented on RESCA-Z₀₁₈₅. The optimized synthesis method was: 1.5–2.5 GBq of cyclotron produced fluorine-18 were trapped on a QMA cartridge and eluted with saline solution to react with 12 nmol of AlCl₃ and form Al[¹⁸F]F. The respective RESCA-conjugated Affibody molecule (14 nmol) in NaOAc solution was added to the Al[¹⁸F]F solution and left to react at 60 °C for 12 min. The mixture was purified on a NAP5 size exclusion column and then analyzed by HPLC. The entire process took approximately 35 min, was highly reproducible, indicating the efficiency and reliability of the method. The labeled compounds demonstrated retained biological function for their respective targets after purification.

Conclusions

We present a general and optimized method for Al[¹⁸F]F labeling of RESCA-conjugated Affibody molecules, which can be widely applied to this class of peptide-based imaging agents. Moreover, radiochemical yields were improved when the labeling was conducted at 37 °C or above. In vitro and in vivo assessment of the respective tracers was promising, showing retained binding capacity as well as moderate defluorination, which is usually regarded as a potential downside for RESCA-conjugated tracers.