Laser Research Centre, Faculty of Physics, Vilnius University, Vilnius, Lithuania; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada; Department of Physics, University of Toronto, Toronto, Ontario, Canada.
Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada; Department of Physics, University of Toronto, Toronto, Ontario, Canada.
Biophys J. 2023 Oct 3;122(19):3924-3936. doi: 10.1016/j.bpj.2023.08.016. Epub 2023 Aug 22.
Second-harmonic generation (SHG) in biological tissues originates predominantly from noncentrosymmetric fibrillar structures partially oriented within a focal volume (voxel) of a multiphoton excitation microscope. This study is aimed to elucidate fibrillar organization factors influencing SHG intensity, as well as achiral, R, and chiral, C, nonlinear susceptibility tensor component ratios. SHG response is calculated for various configurations of fibrils in a voxel using the digital nonlinear microscope. The R and C ratios are calculated using linear incident and outgoing polarization states that simulate polarization-in polarization-out polarimetric measurements. The investigation shows strong SHG intensity dependence on parallel/antiparallel fiber organization. The R and C ratios are strongly influenced by the fiber chirality, tilting of the fibers out of the image plane, and crossing of the fibers. The computational modeling provides the basis for the interpretation of polarimetric SHG microscopy images in terms of the ultrastructural organization of fibers in each voxel of the samples. The modeling results are employed in the accompanying paper to investigate the ultrastructures with parallel/antiparallel fibers and two-dimensional and tree-dimensional crossing fibers in biological and biomimetic structures.
二次谐波产生（SHG）在生物组织中主要源自于在多光子激发显微镜的焦体积（体素）内部分取向的非中心对称纤维状结构。本研究旨在阐明影响 SHG 强度的纤维状组织因素，以及非手性、R 和手性、C 非线性介电张量分量比。使用数字非线性显微镜，针对体素中各种纤维构型计算了 SHG 响应。使用模拟偏振-偏振出偏振测量的线性入射和出射偏振态计算了 R 和 C 比。研究表明，SHG 强度强烈依赖于纤维的平行/反平行组织。纤维的手性、纤维出离图像平面的倾斜以及纤维的交叉都会强烈影响 R 和 C 比值。计算模型为解释样品每个体素中纤维的超微结构组织的偏振 SHG 显微镜图像提供了基础。建模结果用于随附论文中研究具有平行/反平行纤维以及二维和三维交叉纤维的生物和仿生结构的超微结构。
