CHEMOKINE RECEPTORS BASED NANOAGENTS IMAGING ATHEROSCLEROSIS

描述(由申请人提供)：在过去的十年中，动脉粥样硬化病变的分子成像取得了显著的进展。大多数研究都集中在基于多肽的探针上，这种探针是单价的，从体循环中迅速清除，导致靶向效率和对比度较低。因此，由于药物动力学和多价性的可调性，越来越多的人致力于使用基于纳米颗粒的分子探针进行靶向斑块成像。在各种纳米平台中，核壳聚合物纳米颗粒因其灵活的结构设计和精确的官能团控制而备受关注。在动脉粥样硬化病变上上调的一系列生物标志物中，趋化因子受体是很有希望的靶点，因为它们在疾病的初始和发展中起着关键作用。最近，我们开发了靶向趋化因子受体的梳状纳米颗粒，与新的多肽结合，并用64Cu标记，用于动脉粥样硬化的PET成像。这些靶向纳米制剂在实验小鼠ApoE-/-模型中表现出了敏感性和靶向性。在拟议的项目中，我们将优化针对一组趋化因子受体的病毒巨噬细胞蛋白-II(vMIP-II)结合的梳状纳米粒和针对CCR5的D-丙氨酸-多肽T-酰胺(DAPTA)结合的梳状纳米粒的构建。我们的初步PET成像显示，在ApoE-/-小鼠的主动脉弓中，64Cu-vMIP-comb和64Cu-DAPTA-comb特异积聚。然而，靶向效率和目标背景比仍需进一步提高。因此，我们将增加每个梳状纳米颗粒上连接的vMIP-II肽的数量，并优化聚乙二醇化以提高靶向效率，减少血液循环，最大限度地减少非特异性结合。首选的vMIP-Comb将用于检测动脉粥样硬化早期的敏感性和特异性。对于DAPTA-COMB，我们将遵循相同的策略来优化纳米结构，用于CCR5+细胞系的体外筛选。候选DAPTA-Com将在有显著损害的ApoE-/-小鼠身上进行评估(特定目标1)。然后，我们将使用候选的vMIP-comb和DAPTA-comb来确定它们是否可以检测到动脉粥样硬化负荷或进展的变化。我们将进一步分析动脉粥样硬化病变中与放射性标记纳米颗粒相关的特定细胞类型。 并将两种纳米试剂所获得的PET信号与病理检查相关联，包括斑块面积和巨噬细胞面积(特异性目标2)。我们期望靶向纳米颗粒将提供对斑块趋化因子受体的灵敏和特异的检测，并作为有用的工具来检测动脉粥样硬化斑块的负担和进展。

DESCRIPTION (provided by applicant): Remarkable progress has been made over the past decade in the molecular imaging of atherosclerotic lesion. The majority of studies have focused on the peptide based probes, which is monovalent and rapidly cleared from systemic circulation, leading to low targeting efficiency and contrast ratio. Thus, more and more efforts are toward using nanoparticle based molecular probe for targeted plaque imaging due to the tunable pharmacokinetics and multivalency. Of various nanoplatforms, core-shell polymeric nanoparticles are of particular interest owing to the flexible design of structures with accurate control of functional groups for multi- applications. Among an array of biomarkers upregulated on atherosclerotic lesion, chemokine receptors are promising targets owing to their critical roles in the initialization and progression of disease. Recently, we have developed chemokine receptors targeted Comb nanoparticles conjugated with novel peptides and labeled with 64Cu for atherosclerosis PET imaging. These targeted nanoagents demonstrated the sensitivity and targeting specificity in experimental mouse ApoE-/- model. In the proposed project, we will optimize the construction of viral macrophage protein-II (vMIP-II) conjugated Comb nanoparticles targeting a group of chemokine receptors and D-ala-peptide T-amide (DAPTA) conjugated Comb nanoparticles specifically targeting CCR5. Our preliminary PET imaging showed specific accumulation of 64Cu-vMIP-Comb and 64Cu-DAPTA-Comb at the aortic arch in ApoE-/- mice. However, the targeting efficiency and target-to-background ratio need further improvement. Thus, we will increase the number of vMIP-II peptide conjugated on each Comb nanoparticle and optimize the pegylation for enhanced targeting efficiency and reduce the blood circulation for minimized non-specific binding. The preferred vMIP-Comb will be used to determine the sensitivity and specificity in early stage of atherosclerosis. For DAPTA-Comb, we will follow the same strategy to optimize the nanostructure for in vitro screening in CCR5+ cell line. The candidate DAPTA-Com will be evaluated in ApoE-/- mice with significant lesion (Specific Aim 1). Then we will use the candidate vMIP-Comb and DAPTA-Comb to determine whether they can detect variation in atherosclerosis burden or progression. We will further analyze the specific cell type associated with radiolabeled nanoparticles in atherosclerotic lesion and correlate the PET signals obtained with the two nanoagents to the pathological examination including plaque area and macrophage area (Specific Aim 2). We anticipate that the targeted nanoparticles will provide sensitive and specific detection of chemokine receptors at plaque and serve as useful tools to detect the burden and progression of atherosclerotic plaque.