Novel Microparticle Contrast Agent for Near Infrared Molecular Imaging

描述（由申请人提供）：分子成像技术在临床前研究中已经证明了有效性，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造影剂的发展，这些造影剂通常由与肽，抗体或纳米颗粒偶联的荧光团组成。光学成像的两个潜在缺陷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。我们建议研究一种用于炎症光学成像的新型微颗粒造影剂。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。微泡的平均直径为2.5微米，配体（抗体、肽和糖缀合物）可以很容易地偶联到微泡的表面，用于分子成像。微泡造影剂可用于成像管腔血管内皮上表达的分子靶点；针对与炎症和血管生成相关的各种分子的微泡已经在小鼠研究中证明了有效性。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。在给药后几分钟内，未保留在靶部位的微泡被清除到肝、脾和肺，提供异常低的背景对比度信号。此外，微气泡可以很容易地被高强度超声波破坏。这导致气体核的溶解和脂质壳的破碎。在超声分子成像的背景下，这一特性使用户能够在相同的成像设置中使用顺序的造影剂；目标组织内的病原体在扫描之间通过组织超声清除。我们假设携带NIRF报告因子的微泡可能是内皮分子目标光学成像的有效造影剂。相对于单分子造影剂，微泡的大尺寸使得荧光团的有效载荷显著增加，并且由于微泡在血管内的限制，可能产生更大的特异性。此外，从目标组织中清除微泡的能力可以在相同的成像设置中实现多个分子目标的高通量光学成像。我们的目标是用一种针对促炎分子靶点p -选择素的抗体衍生出我们的微泡平台，并在微泡的表面和外壳内偶联一个NIRF报告因子1)。我们将通过活体显微镜评估这些微气泡在体外和体内结合重组p -选择素的能力。最后，我们将利用NIRF全身光学成像技术评估这些药物在小鼠炎症模型中检测p -选择素表达的功效。该项目的成功完成将产生一种用于光学成像的造影剂，可以显著提高吞吐量，并很容易向现有的光学成像用户销售。

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.