Novel Microparticle Contrast Agent for Near Infrared Molecular Imaging

描述（由申请人提供）：分子成像技术已证明在临床前研究中的有效性，主要用于药物发现和基础科学。由于易于使用的造影剂和具有成本效益的成像设备的可用性，光学成像已成为该领域的市场领导者。最近，近红外（NIRF）成像已经看到了许多高灵敏度的造影剂，其通常由荧光团耦合到肽，抗体或纳米颗粒的发展。光学成像的两个潜在缺点与造影剂的目标与背景比以及清除造影剂所需的时间有关。我们提出了一种新的微粒造影剂的光学成像炎症。Targeson开发了一种气体封装的微泡，目前用作超声成像的造影剂。微泡具有2.5 μ m的平均直径，并且配体（抗体、肽和糖缀合物）可以容易地偶联到微泡的表面以用于分子成像的目的。微泡造影剂可用于对管腔血管内皮上表达的分子靶点进行成像;靶向与炎症和血管生成相关的各种分子的微泡已在小鼠研究中证明有效。微泡的靶特异性部分是由于微泡被限制在血管内空间，使其成为纯粹的血管内示踪剂。未保留在靶部位的微泡在给药后几分钟内被清除到肝脏、脾脏和肺部，提供异常低的背景对比信号。此外，高强度超声可以很容易地破坏微泡。这导致气体核的溶解和脂质壳的碎裂。在超声分子成像的背景下，该属性使用户能够在相同的成像设置中连续施用造影剂;通过组织的超声辐照在扫描之间清除靶组织内的药剂。我们假设，一个微泡轴承近红外荧光报告可能是一个有效的造影剂的光学成像内皮分子的目标。微泡相对于单分子造影剂的大尺寸使得荧光团的有效载荷显著更大，并且由于微泡的血管内限制而可以产生更大的特异性。另外，从靶组织清除微泡的能力可以使得能够在相同成像设置内对多个分子靶进行高通量光学成像。我们的目标是用抗促炎分子靶点P-选择素的抗体衍生化我们的微泡平台，并在微泡的表面上和2）壳内缀合NIRF报告子。我们将评估这些微泡的能力，结合重组P-选择素在体外和体内的活体显微镜。最后，我们将使用NIRF全身光学成像评估这些药物检测炎症小鼠模型中P-选择素表达的功效。该项目的成功完成将导致用于光学成像的造影剂，其可以显著增加吞吐量，并且易于向现有的光学成像用户销售。 公共卫生相关性：能够检测分子组分的探针有可能加速药物发现，加强基础研究，并提高临床环境中疾病检测的灵敏度。光学成像广泛用于研究应用，并提供了一种不需要电离辐射的具有成本效益和可再现的成像技术。本文所述的光学成像造影剂将使临床前研究环境中光学成像的通量和多功能性大幅增加。

DESCRIPTION (provided by applicant): Molecular imaging techniques have demonstrated efficacy in the setting of preclinical research, primarily for drug discovery and basic science. Optical imaging has emerged as a market leader in the field, owing to the availability of easy-to-use contrast agents and cost-effective imaging equipment. Recently, near-infrared (NIRF) imaging has seen the development of numerous highly sensitive contrast agents, which generally consist of a fluorophore coupled to a peptide, antibody, or nanoparticle. Two potential drawbacks to optical imaging are related to the target-to-background ratio of the contrast agents, and the time required for clearance of the contrast. We propose to investigate a novel micro particle contrast agent for optical imaging of inflammation. Targeson has developed a gas-encapsulated micro bubble that is currently used as a contrast agent for ultrasound imaging. The micro bubbles have a mean diameter of 2.5 um, and ligands (antibodies, peptides, and glyococonjugates) can be readily coupled to the surface of the micro bubble for the purpose of molecular imaging. The micro bubble contrast agent is useful for imaging molecular targets expressed on the luminal vascular endothelium; micro bubbles targeted to various molecules of relevance to inflammation and angiogenesis have demonstrated efficacy in mouse studies. The target specificity of the micro bubble is in part due to the confinement of the micro bubble to the intravascular space, rendering it a purely intravascular tracer. Micro bubbles that are not retained at the target site are cleared to the liver, spleen and lungs within minutes after administration, providing an exceptionally low background contrast signal. Additionally, micro bubbles can be readily destroyed by high-intensity ultrasound. This results in dissolution of the gas core and fragmentation of the lipid shell. In the context of ultrasound molecular imaging, this property enables users to administer sequential contrast agents in the same imaging setting; agents within the target tissue are cleared between scans by insonation of the tissue. We hypothesize that a micro bubble bearing a NIRF reporter could be an efficacious contrast agent for optical imaging of endothelial molecular targets. The large size of the micro bubble relative to single-molecule contrast agents enables a significantly larger payload of fluorophore, and may yield greater specificity owing to the intravascular confinement of the micro bubble. Additionally, the ability to clear the micro bubbles from the target tissue may enable high-throughput optical imaging of multiple molecular targets within the same imaging setting. We aim to derivatize our micro bubble platform with an antibody against the pro-inflammatory molecular target P-selectin, and conjugate a NIRF reporter 1) on the surface and 2) within the shell of the micro bubble. We will assess the ability of these micro bubbles to bind recombinant P-selectin in vitro and in vivo by intravital microscopy. Finally, we will assess the efficacy of these agents to detect P-selectin expression in a mouse model of inflammation using NIRF whole body optical imaging. Successful completion of this project will result in a contrast agent for optical imaging that could enable a significant increase in throughput, and be readily marketed to existing optical imaging users. PUBLIC HEALTH RELEVANCE: Probes able to detect molecular components have the potential to accelerate drug discovery, enhance basic research, and improve the sensitivity of disease detection in a clinical setting. Optical imaging is widely used in research applications, and provides a cost-effective and reproducible imaging technique that does not require ionizing radiation. The optical imaging contrast agents described here will enable a substantial increase in the throughput and versatility of optical imaging in the preclinical research setting.