Development of efficiently conjugatable hybrid bimodal synthons with radionuclide and fluorescent dye applicable in combined PET/OI

成像模式正电子发射断层扫描（PET）和光学荧光成像（OI）目前没有组合用于肿瘤成像应用，尽管组合方法可以提供重要的优势：PET能够高灵敏度地可视化整个身体的肿瘤组织，而在随后的治疗性手术干预期间的光学荧光成像允许可靠地识别肿瘤边界，封闭的小转移瘤和也转化的恶性淋巴结，因此具有提高治疗效率的潜力，对于这样的组合成像方法，必须开发允许通过两种成像模式可视化的混合标记物。不存在能够有效引入两种标记的杂交双峰互补子在一些实施方案中，缀合的肿瘤-亲和配体（放射性核素和荧光染料）在肿瘤-亲和配体的单个位置中被标记，并且此外表现出足够高的稳定性，与缀合的肿瘤-亲和配体的生物分布的仅微小改变相结合。因此，本项目的目标是开发这种混合双峰双光子。对于这种发展，不同的荧光团（发射从可见光到近红外光谱的光）和螯合剂（可以用68 Ga和64 Cu标记）将被组合，并且所获得的双光子将被功能化，使得它们与生物分子的有效和化学选择性缀合变得可行。这些杂合体的化学合成之后，将对其进行放射性标记并证明其具有足够的稳定性。此外，将在亲水性方面对杂合双链子进行化学优化，以使引入肿瘤-亲和配体中的杂合双链子对所获得的缀合物的生物分布的影响最小化。将不同的开发的杂合双光子与肿瘤-仿射模型物质缀合将在体外评价结合物的放射性标记和结合亲和力（GRPR结合肽二聚体）以及结合物对其靶受体的放射性标记和结合亲和力。最后通过小动物PET/CT和小动物荧光成像评估所获得的双重标记的肿瘤-亲和配体在荷瘤小鼠体内的药代动力学和肿瘤累积，以显示杂合双链体在生物分子衍生化和随后的诊断肿瘤PET和荧光成像中的适用性。

The imaging modalities Positron Emission Tomography (PET) and Optical Fluorescence Imaging (OI) are currently not used in combination for tumor imaging applications, although a combined approach could offer important advantages: PET enables the highly sensitive visualization of tumorous tissues throughout the body whereas optical fluorescence imaging during a following curative surgical intervention allows for the reliable identification of tumor boundaries, enclosed small metastases and also transformed malignant lymph nodes and thus has the potential to increase the therapeutic efficiency.For such a combined imaging approach, hybrid markers have to be developed which allow for a visualization by both imaging modalities.So far, there are no hybrid bimodal synthons available which enable the efficient introduction of both markers (radionuclide and fluorescent dye) in a single position of a tumor-affine ligand and furthermore exhibit a sufficiently high stability combined with an only minor alteration of the biodistribution of the conjugated tumor-affine ligand. Thus, the aim of this project is to develop such hybrid bimodal synthons.For this development, different fluorophores (emitting light extending from the visible to the near-infrared spectrum) and a chelator (which can be labeled with 68Ga und 64Cu) are to be combined and the obtained synthons are to be functionalized so that their efficient and chemoselective conjugation to biomolecules becomes feasible. The chemical syntheses of these hybrid synthons are to be followed by their radiolabeling and demonstration of sufficient stability. Furthermore, the hybrid synthons will be chemically optimized regarding hydrophilicity to minimize the influence of the introduced hybrid synthons into tumor-affine ligands on the biodistribution of the obtained conjugates.As proof-of-concept, different of the developed hybrid synthons are to be conjugated to a tumor-affine model substance (GRPR-binding peptide dimer) and the radiolabeling and binding affinity of the conjugates to their target receptor are to be evaluated in vitro. The obtained, dually labelled tumor-affine ligands are finally to be evaluated regarding their pharmacokinetics and tumor accumulation in vivo in tumor-bearing mice via small animal PET/CT and small animal fluorescence imaging to show the applicability of the hybrid synthons in biomolecule derivatization and subsequent diagnostic tumor PET and fluorescence imaging.