In Vivo Monitoring of Oxygenation in Implants: Applications to Tissue Engineering

描述(由申请人提供)：长期监测生物医学植入物水平上的氧浓度，并优化其可用性是诊断学、组织工程和生物技术的关键问题。EPR可检测氧敏感探针的最新进展，具有极好的灵敏度、准确性和远程可访问性，为实时监测体内氧合开辟了一个新时代。然而，对于许多应用，这些探针需要被封装在半透膜后面。我们开发了一种纳滤器受限的可植入模型设备，具有基于EPR的双重氧气传感器和药物输送能力，并在包含骨髓前体细胞的组织工程构建中测试了其跟踪氧合的能力。使用植入物附近氧气扩散的定量模型，我们还证明了我们的氧传感器提供了报告的局部pO2与微血管密度之间的比例关系，并得到了实验结束时的现场观察的支持。此外，我们还合成了一类新型的生物材料，通过静电纺丝将EPR敏感的纳米晶体直接加入到聚己内酯微纤维支架中。利用EPR成像，我们显示了该支架内氧气的体内分布，并发现所测定的平均PO2与其皮下位置相一致。此外，我们还证实了该支架支持骨髓前体细胞的增殖和内皮分化的能力。在此，我们建议进一步验证、改进设计，扩大该装置的应用范围。该项目除了考虑设备的开发和使用的后勤外，还将考虑其与组织的接口设计，目的是开发一种工具，用于研究和优化依赖于附近新生血管的植入物氧合。具体目标：1.确定组织工程结构中的氧合作用取决于它们的血管形成。2.测试有滤器限制的种植体内的氧合作用对附近血管生成的药物调节敏感的假设。3.用组织工程方法刺激种植体周间隙新生血管也能提高种植体的氧合能力。植入氧探头的使用进展将很容易转化为新的临床应用，如监测组织工程结构中的可用氧，改善灌流，优化细胞包裹，或更好地发挥氧或葡萄糖传感器的功能。 公共卫生相关性：我们建议开发一种方法和植入性设备，用于对生物医学植入物中的局部氧气浓度进行微创活体监测。这将有助于监测氧气依赖传感器、微囊化细胞、组织工程结构以及再生医学的其他分支。

DESCRIPTION (provided by applicant): Long term monitoring of oxygen concentrations at the level of biomedical implants, and optimizing its availability are key issues in diagnostics, tissue engineering and biotechnology. Recent advances in the use of EPR detectable, oxygen-sensitive probes with excellent sensitivity, accuracy and remote accessibility, opened a new era of opportunity for real-time monitoring of oxygenation in vivo. However, for many applications these probes need to be encapsulated behind a semi-permeable membrane. We developed a nanofilter-limited, implantable model device with dual EPR-based oxygen sensor and drug delivery capabilities, and we tested its capacity to track oxygenation in a tissue engineered construct containing bone marrow progenitor cells. Using a quantitative model of oxygen diffusion in the vicinity of implants, we also demonstrated that our oxygen sensor provides a proportional relationship between the reported local pO2 and microvascular density, supported by in situ observations at the end of the experiment. Furthermore, we synthesized a novel class of biomaterials, incorporating by electrospinning the EPR sensitive nano-crystals directly into a poly-caprolactone microfibrillar scaffold. Using EPR imaging, we showed the in vivo distribution of oxygen within this scaffold and found that the determined average pO2 was compatible with its subcutaneous location. In addition, we demonstrated the capacity of this scaffold to support proliferation and endothelial differentiation of bone marrow progenitor cells. Here we propose to further validate, improve the design and expand the applications of this device. This project will take into consideration, besides the development of the device and the logistics of its use, also the design of its interface with the tissue, with the goal to develop a tool for studying and optimizing implant oxygenation as dependent on nearby neovascularization. Specific Aims: 1. Determine oxygenation within tissue engineering constructs as dependent on their vascularization. 2. Test the hypothesis that oxygenation within a filter-limited implant is sensitive to pharmacological modulation of nearby angiogenesis. 3. Demonstrate that stimulation of neovascularization in peri-implant space using tissue engineering methods could also improve implant oxygenation. The progress in the use of implanted oxygen probes will be readily translated into novel clinical applications such as monitoring available oxygen in tissue engineering constructs, with improved perfusion, optimized cell encapsulation, or better functioning of oxygen or glucose sensors. PUBLIC HEALTH RELEVANCE: We propose to develop a method and an implantable device for minimally invasive, in vivo monitoring of local oxygen concentrations in biomedical implants. These will be useful for monitoring oxygenation in oxygen- dependent sensors, in encapsulated cells, in tissue engineering constructs, and for other branches of regenerative medicine.