Nanyang Technological University, School of Chemical and Biomedical Engineering, Singapore.
J Biomed Opt. 2022 Jul;27(7):070901. doi: 10.1117/1.JBO.27.7.070901. Epub 2022 Jul 22.
Deep tissue noninvasive high-resolution imaging with light is challenging due to the high degree of light absorption and scattering in biological tissue. Photoacoustic imaging (PAI) can overcome some of the challenges of pure optical or ultrasound imaging to provide high-resolution deep tissue imaging. However, label-free PAI signals from light absorbing chromophores within the tissue are nonspecific. The use of exogeneous contrast agents (probes) not only enhances the imaging contrast (and imaging depth) but also increases the specificity of PAI by binding only to targeted molecules and often providing signals distinct from the background.
We aim to review the current development and future progression of photoacoustic molecular probes/contrast agents.
First, PAI and the need for using contrast agents are briefly introduced. Then, the recent development of contrast agents in terms of materials used to construct them is discussed. Then, various probes are discussed based on targeting mechanisms, molecular imaging applications, multimodal uses, and use in theranostic applications.
Material combinations are being used to develop highly specific contrast agents. In addition to passive accumulation, probes utilizing activation mechanisms show promise for greater controllability. Several probes also enable concurrent multimodal use with fluorescence, ultrasound, Raman, magnetic resonance imaging, and computed tomography. Finally, targeted probes are also shown to aid localized and molecularly specific photo-induced therapy.
The development of contrast agents provides a promising prospect for increased contrast, higher imaging depth, and molecularly specific information. Of note are agents that allow for controlled activation, explore other optical windows, and enable multimodal use to overcome some of the shortcomings of label-free PAI.
由于生物组织对光的高度吸收和散射，利用光进行深层组织无创高分辨率成像是具有挑战性的。光声成象（PAI）可以克服纯光学或超声成象的一些挑战，提供高分辨率的深层组织成象。然而，来自组织内光吸收色素的无标记 PAI 信号是非特异性的。外源性对比剂（探针）的使用不仅增强了成像对比度（和成像深度），而且通过仅与靶向分子结合，并且通常提供与背景不同的信号，增加了 PAI 的特异性。
我们旨在综述光声分子探针/对比剂的当前发展和未来进展。
首先，简要介绍了 PAI 和使用对比剂的必要性。然后，讨论了用于构建对比剂的材料的最新发展。然后，根据靶向机制、分子成像应用、多模态用途以及在治疗诊断应用中的用途，讨论了各种探针。
正在使用材料组合来开发高特异性的对比剂。除了被动积累之外，利用激活机制的探针显示出更大可控性的潜力。几种探针还能够与荧光、超声、拉曼、磁共振成像和计算机断层扫描同时进行多模态使用。最后，靶向探针也被证明有助于局部和分子特异性的光诱导治疗。
对比剂的发展为提高对比度、增加成像深度和提供分子特异性信息提供了有希望的前景。值得注意的是，允许控制激活、探索其他光学窗口并实现多模态使用的试剂可以克服无标记 PAI 的一些缺点。
