EAGER: Carbon dioxide (CO2) microbubbles-based ultrasonically responsive pressure sensor

测量心脏腔室内或心血管系统其他特定位置的血压的能力对于心脏病的早期诊断和治疗至关重要。理想情况下，这些测量应该是非侵入性的。测量压力的一种方法是将直径约为1微米的非常小的气泡（称为“微泡”）注入血液中。微泡通过响应于超声波束而快速收缩和膨胀来工作。膨胀和收缩的频率可以用来测量气泡附近的压力。然而，使用这种方法很难检测到可能表明健康问题的非常小的压力变化。该研究项目涉及探索一种新的方案来涂覆这些气泡，使它们更稳定，对局部血压的变化更敏感。研究人员正在制作和表征一个涂层材料库，然后测试涂层将增强气泡对周围压力的响应的想法。如果成功，这种方法可以使涂层微泡在一系列超声诊断中的使用成为可能。该研究项目还涉及对学生和青年研究人员进行实验方法培训，并正在开展若干外联活动，包括研究开放日和面向公众的科学讲座。在该项目中，研究人员正在开发结合联合收割机微流体、流变学、聚合物合成和石墨烯化学的方法，以生产和表征聚乙二醇-氧化石墨烯（PEG-GO）封装的二氧化碳微泡，并操纵它们的压力敏感性。该研究利用了最近关于交联PEG-GO水凝胶的合成和流变学以及PEG-GO水凝胶涂层在控制微泡的压力响应中的作用的工作。通过系统地改变PEG的分子量和每个GO的反应性官能团的平均数量和类型，合成具有不同性质的PEG-GO材料库。使用核磁共振光谱、红外光谱、热重分析、扫描电子显微镜、原子力显微镜和流变学方法对样品进行表征，以确定结构-性能关系。初步结果表明，水凝胶将稳定二氧化碳微泡。研究人员假设，涂层将通过涂层渗透率随环境压力变化而变化，对压力-气泡尺寸关系产生协同效应。这种修改应该产生气泡尺寸对压力变化的显著响应，这应该允许检测非常小的压力变化。研究人员正在使用微流体平台来生成PEG-GO封装的二氧化碳气泡，然后使用成像来确定它们对压力变化的响应。

The ability to measure blood pressure inside the chambers of the heart or at other specific places in the cardiovascular system is essential to the early diagnosis and treatment of heart disease. Ideally, these measurements should be non-invasive. One approach to measuring pressure involves injecting very small gas bubbles, about one micrometer in diameter, called "microbubbles" into the blood. Microbubbles work by rapidly contracting and expanding in response to an ultrasound beam. The frequency of the expansion and contraction can be used to measure the pressure near the bubble. However, it is difficult to detect the very small changes in pressure that can signal health problems using this approach. This research project involves exploring a novel scheme for coating these bubbles to make them both more stable and more sensitive to changes in the local blood pressure. The researchers are making and characterizing a library of coating materials, and then testing the idea that the coatings will create an enhanced response of the bubble to the surrounding pressure. If successful, this approach could enable the use of coated microbubbles in a range of ultrasound diagnostics. The research project also involves training of students and young researchers in experimental methods, and several outreach activities are being pursued, including research open houses and science lectures for the general public. In this project researchers are developing approaches to combine microfluidics, rheology, polymer synthesis, and graphene chemistry to produce and characterize polyethylene glycol-graphene oxide (PEG-GO) encapsulated carbon dioxide microbubbles and to manipulate their pressure sensitivity. The research leverages recent work on the synthesis and rheology of cross-linkable PEG-GO hydrogels and on the role of the PEG-GO hydrogel coating in controlling the pressure response of the microbubbles. A library of PEG-GO materials with different properties are being synthesized by systematically varying the molecular weight of the PEG and the average number and type of reactive functional groups per GO. Samples are being characterized using nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, atomic force microscopy, and rheometry methods to determine structure-property relationships. Preliminary results suggest that the hydrogel will stabilize carbon dioxide microbubbles. The researchers hypothesize that the coating will produce a synergistic effect on the pressure-bubble size relationship through the variation of the coating permeability as the ambient pressure changes. This modification should produce a dramatic response of bubble size to pressure changes, which should allow detection of very small changes in pressure. The researchers are using microfluidic platforms to generate PEG-GO encapsulated carbon dioxide bubbles and then using imaging to determine their dissolution in response to pressure changes.