Magnetic Particle Microscopy of Living Organisms

该项目的目标是开发一种新的三维成像技术，利用磁性纳米粒子示踪剂，在活生物体、组织和细胞培养物中观察和研究细胞和亚细胞水平的生物过程。智力成果：光学显微镜和成像技术的进步改变了生物学。然而，由于光在组织内的散射和吸收，光学显微镜的穿透深度是有限的。因此，以高分辨率和来自所需高强度照明的最小光损伤询问超过（0.5至0.8）mm的组织和3D细胞培养物一直是具有挑战性的。相比之下，磁场穿透生物样品而不会散射或伤害细胞，为本文提出的磁性纳米颗粒显微镜的新成像模式提供了机会。细胞和细胞器可以用磁性纳米颗粒示踪剂标记，然后可以以高对比度和分辨率成像。磁性纳米粒子显微镜是基于磁性粒子成像（MPI）的原理。简而言之，建立磁场分布，使得样品内除了小的无场点之外的任何地方的示踪剂颗粒都是磁饱和的。因此，当施加交流激励场时，仅从无场点内的纳米颗粒引起响应。通过扫描样品内的无场点以在空间上选择纳米颗粒并感应地测量它们的响应来构建纳米颗粒浓度的3D图像。对MPI的研究集中在毫米级分辨率扫描仪的开发上，其视野涵盖整个人类或小动物身体。拟议中的研究旨在将磁粒子成像扩展到亚细胞分辨率。实验目标是在相关生物样本中证明25 µm。将实施磁场组件，以提供近两个数量级更精细分辨率所需的高磁场梯度。系统硬件将采用低噪声电子器件设计，以确保最大的信噪比。此外，定制尺寸的纳米颗粒示踪剂和生物相容性涂层将被精确设计以满足成像要求。模块化合成方法将允许核心和生物相容性涂层独立和系统地定制，并进行精确控制。成像能力将在胚胎斑马鱼中得到证明，并通过同步光学显微镜进行验证。为鉴定磁性纳米粒子成像而提出的实验也将推进正在进行的研究，以确定影响纳米粒子摄取的物理和化学性质，从而深入了解其毒性。该项目形成了跨学科和跨机构的合作，桥接工程，化学和生物学，以满足对成像技术的需求，探索微生物学和医学的新科学前沿。细胞和亚细胞分辨率的成功演示将建立一种新的显微镜手段，使用磁性纳米粒子示踪剂，研究光学不透明的活组织中的细胞行为。除了基础生物学，这项工作将推进精确工程纳米粒子的合成技术，并为纳米粒子与生命系统的相互作用带来新的见解。此外，它将为临床皮肤和乳腺癌筛查的医学成像中设想的应用奠定基础。PI将涉及2名研究生和4名本科生的研究。参与的学生将获得全面的技术教育，不仅获得各自专业领域的专业知识，还获得互补研究领域的方法和材料知识。项目中合适的子主题将被整合到PI教授的跨学科和特定学科课程中。研究结果将在相关的高影响力期刊上发表，并在区域、国家和国际技术会议上介绍。此外，如数据管理计划所述，最终数据将存档并向公众提供。PI将通过与小学、初中和高中科学教师合作开发年级适当的教学材料，为K-12教育服务。PI还将参加Science Pubs，这是一项非正式的科学教育计划，旨在让公众参与讨论纳米颗粒在医学和生物学中的合成，应用和影响。

The goal of this project is to develop a new three-dimensional imaging technique, using magnetic nanoparticle tracers, to observe and study biological processes at the cellular and sub-cellular level in live organisms, tissue and cell cultures.Intellectual Merit:Advances in optical microscopy and imaging have transformed biology. However, the penetration depth of optical microscopy is limited due to the scattering and absorption of light within tissue. Thus, interrogating tissue and 3D cell cultures beyond (0.5 to 0.8) mm with high resolution and minimal photodamage from the required high-intensity illumination has been challenging. Magnetic fields, in contrast, penetrate biological samples without scattering or harm to the cells, providing the opportunity for a new imaging modality from magnetic nanoparticle microscopy as proposed here. Cells and cellular organelles may be labeled with magnetic nanoparticle tracers, which can then be imaged with high contrast and resolution. Magnetic nanoparticle microscopy is based on the principles of magnetic particle imaging (MPI). Briefly, a magnetic field distribution is established such that tracer particles everywhere within the sample except a small field free point are magnetically saturated. As a result, when an ac excitation field is applied, a response is elicited only from nanoparticles within the field free point. A 3D image of the nanoparticle concentration is constructed by scanning the field free point within the sample to spatially select the nanoparticles and measure their response inductively. Research on MPI has focused on the development of millimeter-scale resolution scanners with a field of view encompassing the whole human or small animal body. The proposed research seeks instead to scale magnetic particle imaging for sub cellular resolution. The experimental goal is to demonstrate 25 µm in a relevant biological specimen. A magnet field assembly will be implemented to provide the high field gradient needed for nearly two orders of magnitude finer resolution. The system hardware will be designed with low noise electronics to ensure maximal signal-to-noise ratio. Further, nanoparticle tracers of custom size and biocompatible coatings will be precision engineered with to meet the imaging requirements. A modular synthetic approach will allow the core and biocompatible coatings to be independently and systematically tailored, with exquisite control. Imaging capabilities will be demonstrated in embryonic zebrafish and verified via concurrent optical microscopy. Experiments proposed to qualify magnetic nanoparticle imaging will also advance ongoing research in identifying physical and chemical properties of nanoparticles that influence their uptake and thereby provide insight to their toxicity.Broader Impact: This project forges an interdisciplinary and inter-institutional collaboration, bridging engineering, chemistry and biology, to meet the need for an imaging technology to explore new scientific frontiers in microbiology and medicine. The successful demonstration of cellular and sub cellular resolution will establish a new means of microscopy, using magnetic nanoparticle tracers, to investigate cell behavior in optically opaque, living tissue. Beyond fundamental biology, this effort will advance synthesis techniques for precisely engineered nanoparticles and bring new insight to nanoparticle interactions with living systems. Further, it will lay the foundation for applications envisioned in medical imaging of clinical skin and breast cancer screening. The PIs will involve 2 graduate and 4 undergraduate students in research. The participating students will gain a well-rounded technical education acquiring not only expertise in their respective areas of specialization but also knowledge of methods and materials in complementary areas of research. Suitable sub-topics within the project will be integrated in to cross disciplinary and discipline-specific courses taught by the PIs. The research findings will be published in relevant high-impact journals and presented at regional, national and international technical meetings. In addition, as discussed in the data management plan, final data will be archived and made available to the public. The PIs will serve K-12 education by developing grade-level appropriate instruction materials in collaboration with elementary, middle and high school science teachers. The PIs will also participate in Science Pubs, an informal science education program to engage the public in discussion on the synthesis, applications and implications of nanoparticles in medicine and biology.