Vibrational Photoacoustic Microscopy for Bond-selective Tissue Analysis

描述(由申请人提供)：我们研究的一个长期目标是通过开发无标记显微镜来寻求对分子功能在健康和疾病中的新理解。在R21的应用中，我们开发了一种名为振动光声显微镜(VPA)的新方法，用于对具有毫米级视野和穿透深度的组织进行三维振动成像。我们的方法是基于分子泛音振动的激发和组织中产生的压力波的声学检测。我们的方法在以下方面具有重要意义：(I)泛音激发以一种无标记的方式提供了化学键的选择性和光谱信息。(Ii)声学探测消除了近红外光谱学中遇到的组织散射问题，并能够在一次扫描中进行深度分辨信号收集。(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达到的。通过激发C-H键的第二泛音，在血液干扰最小的8300厘米-1附近，我们已经展示了组织模体和动脉中动脉粥样硬化斑块的初步VPA成像，穿透深度在毫米尺度上。这些结果表明，发展VPA显微镜和内窥镜在活体动物以及最终在患者中进行脂质相关疾病的无标记分子成像和光谱分析方面具有巨大的潜力。这两个具体目标是：(1)开发高速VPA显微镜，用于活体分子成像和定量分析；(2)开发VPA光谱和内窥镜，用于原位、深度分辨表征动脉粥样硬化斑块。VPA显微镜的成功开发将提供一个新的平台，使生物样品的体外和体内无标记分子成像和光谱分析成为可能。对于动脉粥样硬化等疾病的诊断，VPA光谱辅助主成分分析应该能够确定病变的分期，因为它能够识别整个深层组织的不同病理生理成分。此外，我们内窥镜的发展有望将VPA方法推向活体斑块成像。 公共卫生相关性：(由申请人提供)：由于目前成像工具的空间分辨率和/或化学选择性有限，心血管疾病中易损斑块的活体成像是困难的。我们发展了一种名为振动光声显微镜的新方法，用于在毫米尺度上对具有视场和穿透深度的组织进行三维振动成像。成功开发的血管内振动光声探头具有以无标记方式检测易损斑块的潜力。

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. PUBLIC HEALTH RELEVANCE: (provided by applicant): Intravital imaging of vulnerable plaques in cardiovascular diseases is difficult due to limited spatial resolution and/or chemical selectivity of current imaging tools. We develop a new method termed vibrational photoacoustic microscopy for 3-D vibrational imaging of tissues with a field of view and a penetration depth both in the mm scale. Successful development of an intravascular vibrational photoacoustic probe holds the potential of detecting vulnerable plaques in a label free manner.