Vibrational Photoacoustic Microscopy for Bond-selective Tissue Analysis

描述（由申请人提供）：我们研究的长期目标是通过无标记显微镜的发展，对健康和疾病中的分子功能进行新的理解。在这个R21应用程序中，我们开发了一种新的方法，称为振动光声（VPA）显微镜的3-D振动成像的组织与视野和穿透深度都在毫米级。我们的方法是基于激发的分子泛音振动和声学检测所产生的压力波在组织中。我们的方法在以下几个方面是有意义的：（i）泛音激发提供化学键的选择性和光谱信息，在一个标记的方式。(ii)声学检测消除了近红外光谱中遇到的组织散射问题，并在一次扫描中实现了深度分辨信号收集。(iii)我们的方法提供了几毫米的组织穿透深度，这是现有的振动显微镜无法访问。通过激发约8300 cm-1的C-H键拉伸的第二泛音，其中血液干扰最小，我们已经证明了初步的VPA成像的组织幻影和动脉粥样硬化斑块在动脉中的穿透深度在毫米尺度。这些结果表明，开发VPA显微镜和内窥镜用于活体动物和最终患者中脂质相关疾病的无标记分子成像和光谱分析的巨大潜力。两个具体目标是（1）开发用于体内分子成像和定量分析的高速VPA显微镜，以及（2）开发用于动脉粥样硬化斑块原位深度分辨表征的VPA光谱学和内窥镜。VPA显微镜的成功开发应该提供一个新的平台，使无标记的分子成像和光谱分析的生物标本离体和体内。对疾病的诊断，如动脉粥样硬化，VPA光谱辅助主成分分析应允许病变阶段的确定，由于在整个深部组织中识别不同的病理生理成分的能力。此外，我们的内窥镜发展有望将VPA方法推向斑块的活体成像。

DESCRIPTION (provided by applicant): A long term goal of our research is pursuing new understanding of molecular functions in health and disease via development of label-free microscopy. In this R21 application, we develop a new method termed vibrational photoacoustic (VPA) microscopy for 3-D vibrational imaging of tissues with a field of view and a penetration depth both in the mm scale. Our method is based on excitation of molecular overtone vibration and acoustic detection of the resultant pressure waves in the tissue. Our approach is significant in the following aspects: (i) Overtone excitation provides chemical bond selectivity and spectroscopic information in a label-free manner. (ii) Acoustic detection eliminates the tissue scattering problem encountered in near-infrared spectroscopy and enables depth-resolved signal collection in one scan. (iii) Our method provides a tissue penetration depth of a few mm, which is not accessible with existing vibrational microscopies. By excitation of the second overtone of the C-H bond stretch around 8300 cm-1, where blood interference is minimal, we have demonstrated preliminary VPA imaging of tissue phantoms and atherosclerotic plaques in arteries with a penetration depth in mm scale. These results show the great potential of developing VPA microscopy and endoscopy for label-free molecular imaging and spectroscopic analysis of lipid-related disorders in live animals and eventually in patients. The two specific aims are (1) developing high-speed VPA microscopy for in vivo molecular imaging and quantitative analysis and (2) developing VPA spectroscopy and endoscopy for in situ, depth resolved characterization of atherosclerotic plaques. Successful development of VPA microscopy should provide a new platform enabling label-free molecular imaging and spectroscopic analysis of biological specimen ex vivo and in vivo. Towards diagnosis of diseases such as atherosclerosis, VPA spectroscopy aided with principal component analysis should allow determination of lesion stages owing to the capability of identifying different pathophysiological compositions throughout deep tissues. Furthermore, our endoscopy development is expected to push the VPA method towards intravital imaging of plaques.