title: Glycerol-mediated nanostructure modification leading to improved transparency of porous polymeric scaffolds for high performance 3D cell imaging.
abstract: Glycerol is among the most commonly used optical clearing agents for tissues clearance largely due to refractive index (RI) matching between glycerol and the submerged tissues. Here we applied glycerol as structure modifier at both macroscopic (as porogen) and nanoscopic (as nanostructure ameliorant) scales to fabricate transparent porous scaffolds made from poly(ethylene glycol) (PEG) as well as other widely used biomaterials (e.g., PLGA, PA, or gelatin), whose nanostructures, in the scale of light wavelength, dominantly improved the optical transmittance of the scaffolds even when immersed in RI mismatched medium (e.g., culture medium or water). We further exploited the clearing mechanisms based on Mie scattering theory, illustrating that conformational changes of polymer chains induced by solvent effects of glycerol enhanced the anisotropy (i.e., directional alignment) of the nanostructures, leading to reduced crystallinity and scattering of the resulted PEG scaffolds. Our findings represent the first and systematic demonstration with both experimental and theoretical evidence in effectively clearing porous polymeric scaffolds by mechanisms other than RI matching, which could tackle the limitations of current optical imaging of cells cultured within three-dimensional (3D) opaque porous scaffolds, such as poor visibility, low spatial resolution, and small penetration depth.
authors.affiliation: Department of Biomedical Engineering, School of Medicine and ‡Department of Physics, Tsinghua University , Beijing 100084, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Zhao
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Shen
authors.forename: Jingyu
authors.initials: J
authors.lastname: Wang
authors.forename: Xiaokang
authors.initials: X
authors.lastname: Li
authors.forename: Yang
authors.initials: Y
authors.lastname: Zeng
authors.forename: Bingjie
authors.initials: B
authors.lastname: Wang
authors.forename: Yonghong
authors.initials: Y
authors.lastname: He
authors.forename: Yanan
authors.initials: Y
authors.lastname: Du
mesh_terms: D016880:Anisotropy; D001672:Biocompatible Materials / Q000737:chemistry; D045744:Cell Line, Tumor; D005990:Glycerol / Q000737:chemistry*; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008027:Light; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry*; D061848:Optical Imaging / Q000379:methods; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D012031:Refractometry; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D054457:Tissue Scaffolds / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D012997:Solvents; D014867:Water; D011092:Polyethylene Glycols; D005990:Glycerol