Development of new peptide based NIR probe conjugates for specifically and selectively detecting amyloid early biomarkers

FluPepDye旨在提供新的选择性NIR荧光环肽，用于特异性检测不同淀粉样蛋白病理学的早期生物标志物，并将淀粉样蛋白结合荧光团转化为有用的研究或临床工具，以帮助淀粉样蛋白相关疾病的早期和可靠诊断。该项目主要关注阿尔茨海默病（AD）中涉及的淀粉样β（1-42）肽（Aβ1-42），旨在将所采用的可调节方法扩展到其他淀粉样蛋白，如α-突触核蛋白，tau和hIAPP，参与其他病理学。虽然已知有超过20种淀粉样蛋白疾病（如神经退行性疾病和II型糖尿病）涉及超过30种淀粉样蛋白，但目前没有任何早期诊断工具可用于这些疾病。在疾病的特定症状出现之前，对退化类型进行早期和精确的诊断至关重要，因为当临床症状出现时，靶器官和细胞（神经退行性疾病中的神经元和糖尿病中的胰腺β细胞）的破坏是不可逆的。在神经退行性疾病的框架中使用非侵入性NIR探针在生物成像领域中已经做出了一些努力，特别是用于AD诊断。尽管其在体内应用中具有有利的特征，但其转化为临床实践仍然具有挑战性，并且仍然需要进一步的光学改进和技术进步。据我们所知，它们中没有一个被设计并被证明仅对一种类型的淀粉样蛋白具有特异性。此外，能够在神经变性的临床前阶段选择性地仅检测可溶性寡聚体的探针迄今尚未报道。本研究计画将著重于设计、合成及评估新的肽基近红外探针共轭物。这些新的荧光分子被认为具有合适的发射波长，具有开启光学特性，对一种特定的淀粉样蛋白及其可溶性早期聚集体的选择性，在生物环境中的高稳定性，以及良好的跨膜渗透性。新的基于肽的探针缀合物将由三个元件组成：作为识别元件的环肽，其将驱动对特定淀粉样蛋白和低聚物种类的选择性，作为用于通过钯催化的交叉偶联反应缀合的锚元件的色氨酸，以及作为提供定制的NIR荧光的示踪元件的荧光探针。这些探针将在生物物理测定中进行评价，以获得有关其荧光特性、结合亲和力、选择性、代谢稳定性和膜渗透性的信息。

FluPepDye aims to provide new selective NIR-fluorescent cyclopeptides for specifically detecting early biomarkers of distinct amyloid pathologies and to translate amyloid-binding fluorophores into useful research or clinical tools for aiding the early and reliable diagnosis of amyloid-related diseases. The project principally focuses on Amyloid β(1-42) peptide (Aβ1-42), involved in Alzheimer’s Disease (AD), and it aims to extend the employed modulable approach to other amyloidogenic proteins such as α-synuclein, tau and hIAPP, involved in other pathologies. While more than 20 amyloid diseases (such as neurodegenerative diseases and type II Diabetes) are known and involve more than 30 amyloid proteins, no early diagnostic tools are currently available for any of these diseases. It is crucial to establish early and precise diagnostics of the type of degeneration before specific symptoms of the disease appear, because when the clinical symptoms are present, the destruction of the target organs and cells (neurons in neurodegenerative diseases and pancreatic β-cells in diabetes) is irreversible. Several efforts have been made in the field of bioimaging using non-invasive NIR probes in the frame of neurodegenerative diseases, particularly for AD diagnosis. Despite their favourable features for their in vivo application, their translation into the clinical practice remains challenging and further optical improvements and technological evolutions are still needed. To our knowledge, none of them has been designed and proven to be specific for only one type of amyloid protein. Furthermore, probes able to detect selectively only soluble oligomers at the pre-clinical stage of neurodegeneration have not been reported to date. This research project will focus on the design, synthesis and evaluation of new peptide based NIR probe conjugates. These new fluorescent molecules are conceived to have suitable emission wavelengths with turn-on optical properties, selectivity for one specific amyloid protein and its soluble early aggregate species, high stability in biological environments, and good permeability across membranes. The new peptide-based probe conjugates will be composed by three elements: a cyclopeptide as recognition element that will drive the selectivity for a specific amyloid protein and for oligomer species, a tryptophan as anchor element for conjugation by palladium catalysed cross-coupling reactions and a fluorescent probe as tracer element providing tailored NIR fluorescence. These probes will be evaluated in biophysical assays to get information on their fluorescent properties, their affinity of binding, their selectivity, their metabolic stability, and their membrane permeability.