Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, 14853, USA.
Optical and Biomedical Engineering Laboratory, School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Perth, WA, 6009, Australia.
Nat Commun. 2018 May 25;9(1):2079. doi: 10.1038/s41467-018-04357-8.
Optical tweezers are an invaluable tool for non-contact trapping and micro-manipulation, but their ability to facilitate high-throughput volumetric microrheology of biological samples for mechanobiology research is limited by the precise alignment associated with the excitation and detection of individual bead oscillations. In contrast, radiation pressure from a low-numerical aperture optical beam can apply transversely localized force over an extended depth range. Here we present photonic force optical coherence elastography (PF-OCE), leveraging phase-sensitive interferometric detection to track sub-nanometer oscillations of beads, embedded in viscoelastic hydrogels, induced by modulated radiation pressure. Since the displacements caused by ultra-low radiation-pressure force are typically obscured by absorption-mediated thermal effects, mechanical responses of the beads were isolated after independent measurement and decoupling of the photothermal response of the hydrogels. Volumetric imaging of bead mechanical responses in hydrogels with different agarose concentrations by PF-OCE was consistent with bulk mechanical characterization of the hydrogels by shear rheometry.
光学镊子是一种非常有价值的非接触式捕获和微操作工具，但由于与单个珠子振动的激发和检测相关的精确对准，其在生物样品高通量体积微流变学中的应用受到限制。相比之下，低数值孔径的光学光束的辐射压力可以在扩展的深度范围内施加横向局部力。在这里，我们提出了光子力光学相干弹性成像（PF-OCE），利用相敏干涉检测来跟踪嵌入粘弹性水凝胶中的珠子的亚纳米级振动，这些振动是由调制的辐射压力引起的。由于超低压射力引起的位移通常被吸收介导的热效应所掩盖，因此在独立测量和水凝胶光热响应解耦后，珠子的机械响应被隔离。通过 PF-OCE 对不同琼脂浓度水凝胶中的珠子机械响应的体积成像与通过剪切流变仪对水凝胶的整体力学特性进行的体积成像一致。
