Biology subjects

Krouglov, S.

Publications and source records attributed to Krouglov, S..

3 recordsLinked to original sources

bioRxiv2023

Polarimetric response of second harmonic generation in microscopy of partially oriented chiral fibrillar structures

Polarimetric second harmonic generation (SHG) microscopy is employed to study partially oriented fibrillar structures. The polarimetric SHG parameters are influenced by three-dimensional (3D) configuration of C6 symmetry fibrilar structures in the focal volume (voxel) of a microscope. The achiral and chiral susceptibility tensor components ratios (R and C, respectively) are extracted from the linear polarization-in polarization-out (PIPO) measurements. The analytical derivations along with the polarimetric SHG microscopy results obtained from rat tail tendon, rabbit cornea, pig cartilage and meso-tetra (4-sulfonatophenyl) porphine (TPPS4) cylindrical aggregates demonstrate that SHG intensity is affected by parallel/antiparallel arrangements of the fibers, and R and C ratio values change by tilting the fibers out of image plane, as well as by crossing the fibers in 2D and 3D. The polarimetric microscopy results are consistent with the digital microscopy modeling of fibrillar structures. These results facilitate the interpretation of polarimetric SHG microscopy images in terms of 3D organization of fibrilar structures in each voxel of the samples. Statement of SignificancePolarimetric second harmonic generation (SHG) microscopy is used to study partially oriented C6 symmetry chiral fibrillar structures. The linear polarization-in polarization-out (PIPO) SHG imaging is performed on rat tail tendon, rabbit cornea, pig cartilage tissues and meso-tetra (4-sulfonatophenyl) porphine (TPPS4) cylindrical aggregates. The study demonstrates that SHG intensity is affected by parallel/antiparallel arrangements of the fibers, and the achiral and chiral susceptibility component ratio values change by tilting the fibers out of image plane, as well as by crossing the fibers in 2D and 3D. The polarimetric microscopy results are consistent with the digital microscopy modeling of fibrillar structures. These results facilitate the interpretation of polarimetric SHG microscopy images in terms of 3D organization of fibrillar structures in each voxel of the samples.

biophysics↗

bioRxiv2022

Digital polarimetric second harmonic generation microscopy of partially oriented fiber structures

Second harmonic generation (SHG) in biological tissue originates predominantly from noncentrosymmetric fibrillar structures partially oriented within the focal volume (voxel) of a multiphoton excitation microscope. The 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 digital nonlinear microscope. The R and C ratios are calculated using linear incident and outgoing polarization states that simulate polarization-in polarization-out (PIPO) polarimetric measurements. The investigation shows strong SHG intensity dependence on parallel/antiparallel fiber organization. The R and C ratio is strongly influenced by the fiber chirality, tilting of the fibers out of image plane and crossing of the fibers. The study facilitates interpretation of polarimetric SHG microscopy images in terms of ultrastructural organization of fibers in the imaged structures. Statement of SignificanceSecond harmonic generation microscopy is widely used for imaging non-centrosymmetric biological structures such as collagen. The ultrastructure of collagen can be determined with polarimetric SHG microscopy. The coherent nonlinear response of biological structures depends on the 3D orientations and positions of the collagen fibers in the focal volume of the microscope. Here, we show how different fiber organizations and 3D orientations in the focal volume can affect the polarimetric SHG responses. The results are important for understanding and interpreting images obtained with polarimetric SHG microscopy.

biophysics↗

bioRxiv2022

Wide-Field Stokes Polarimetric Microscopy for Second Harmonic Generation Imaging

We employ wide-field second harmonic generation (SHG) microscopy together with nonlinear Stokes polarimetry for quick ultrastructural investigation of large sample areas (700 m x 700 m) in thin histology sections. The Stokes vector components for SHG are obtained from the polarimetric measurements with incident and outgoing linear and circular polarization states. The Stokes components are used to construct the images of polarimetric parameters and deduce the sample maps of achiral and chiral nonlinear susceptibility tensor components ratios and cylindrical axis orientation in fibrillar materials. The imaged histology sections with polarimetric wide-field SHG microscopy provide large area maps of ultrastructural information about the collagenous tissue, which can be used for rapid histology investigations.

biophysics↗