Intracellular In vivo Imaging

迄今为止，体内分子成像剂特异性靶向细胞表面或细胞外基质。 微环境然而，大多数癌细胞的高度特异性变化， 癌细胞与正常细胞的分化发生在细胞内。因此， 是开发能够报告胞质内变化的药物， 在体内成像。实现这一目标的第一步是将成像剂靶向于靶向区。 需要对细胞表面标记物具有亲和力的细胞表面。那么配体必须是 通过内吞作用内化，然后结合到适当的位点， 激活。这些要求对合成化学提出了很高的要求 因为分子构建体必须具有多种功能。我们正在开发 智能可激活的光学结构， 内化到细胞质中。使用一系列商业上可获得的染料， 靶向化合物，然后修饰成在特定的细胞内条件下发荧光 如较低的pH值和特定酶活性的存在下，我们正在取得进展， 朝着细胞内体内成像的目标前进。这项工作正在进行中， 与东京大学化学系的Urano教授合作。来 过去一年，我们在这一领域取得了相当大的进展，证明有可能 基于BODIPY和罗丹明主链，产生高度可活化的光学成像剂。 我们还在开创性地努力创造多模态成像剂;可以在 光学照相机以及PET、MR或放射性核素照相机。正在设计的代理人是 高度生物相容性和元素已经用于人类。就目前而言， 我们用罗丹明绿色标记的半乳糖基血清白蛋白（GSA）（GSA-RhG）， 在癌细胞内迅速内化，并且可以作为人类使用的试剂。我们 开发了活化的荧光分子成像剂，并取得了许多成功， 当年然而，我们继续寻求一种只在癌症中激活的解决方案， 而不是在其他正常细胞中。同时对多个目标成像的能力 引导我们探索多激发和多发射相机。我们曾希望一个单一的 激发光将能够激活不同波长的多个荧光团， 事实证明这是不现实的。相反，我们使用多波长激发光， 新的大师相机这使我们能够同时成像近距离的4个目标 红外线，具有很好的临床应用前景

To date, in vivo molecular imaging agents specifically target the cell surface or microenvironment. However, most of the highly specific changes of cancer cells that differentiate cancers cells from normal cells occur intracellularly. The challenge, therefore, is to develop agents that report intracytoplasmic changes yet still are capable of being imaged in vivo. The first step in achieving this goal is to target the imaging agent to the cell surface which requires affinity for a cell surface marker. The ligand must then be internalized by endocytosis and then bind to the appropriate site whereupon it activates. These requirements place large demands on synthetic chemistry since the molecular construct must have multiple functionalities. We are developing smart activatable optical constructs which only fluoresce when they are internalized to the cytoplasm. Using a series of commercially available dyes that are bound to targeting compounds and then modified to fluoresce under specific intracellular conditions such as lower pH and in the presence of specific enzymatic activity we are making progress toward the goal of intracellular in vivo imaging. This work is being performed in collaboration with Prof. Urano from the University of Tokyo Chemistry Department. Over the past year we have made considerable advances in this area by proving that it is possible to create highly activatable optical imaging agents based on the BODIPY and Rhodamine backbones. We are also pioneering efforts to create multimodal imaging agents; agents that can be seen on both optical cameras as well as PET, MR or radionuclide cameras. The agents being designed are highly biocompatible and elements have already been used in humans. For intance, the agent Galactosylserum Albumin (GSA) which we have labeled with Rhodamine Green (GSA-RhG) is internalized rapidly within cancer cells and may be viable as an agent for human use. We are developing activated fluorescent molecular imaging agents and have a number of successes over the year. However, we continue to pursue a solution that will activate only within cancer cells and not within other, normal cells. The ability to image multiple targets simulanteously led us to explore multiexcitation and multiemission cameras. We had hoped that a single excitation light would be able to activate multiple fluorophores at differing wavelengths but this proved to be unrealistic. Instead, we use multiple wavelength excitation light using a new Maestro camera. This has allowed us to simultaneously image up to 4 targets in the near infrared and is very promising for clinical application