Shi Junhui, Wong Terence T W, He Yun, Li Lei, Zhang Ruiying, Yung Christopher S, Hwang Jeeseong, Maslov Konstantin, Wang Lihong V
Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
Nat Photonics. 2019 Sep;13:609-615. doi: 10.1038/s41566-019-0441-3. Epub 2019 May 13.
Mid-infrared (MIR) microscopy provides rich chemical and structural information about biological samples, without staining. Conventionally, the long MIR wavelength severely limits the lateral resolution owing to optical diffraction; moreover, the strong MIR absorption of water ubiquitous in fresh biological samples results in high background and low contrast. To overcome these limitations, we propose a method that employs photoacoustic detection highly localized with a pulsed ultraviolet (UV) laser on the basis of the Grüneisen relaxation effect. For cultured cells, our method achieves water-background suppressed MIR imaging of lipids and proteins at UV resolution, at least an order of magnitude finer than the MIR diffraction limits. Label-free histology using this method is also demonstrated in thick brain slices. Our approach provides convenient high-resolution and high-contrast MIR imaging, which can benefit diagnosis of fresh biological samples.
中红外（MIR）显微镜无需染色就能提供有关生物样品丰富的化学和结构信息。传统上，由于光学衍射，较长的MIR波长严重限制了横向分辨率；此外，新鲜生物样品中普遍存在的水对MIR有强烈吸收，导致背景高且对比度低。为了克服这些限制，我们提出了一种基于格林艾森弛豫效应、利用脉冲紫外（UV）激光进行高定位光声检测的方法。对于培养细胞，我们的方法实现了在紫外分辨率下对脂质和蛋白质进行水背景抑制的MIR成像，其分辨率至少比MIR衍射极限精细一个数量级。使用该方法的无标记组织学也在厚脑切片中得到了证明。我们的方法提供了便捷的高分辨率和高对比度MIR成像，这有助于对新鲜生物样品进行诊断。
