1.2 Nanoscale 3D Mapping of Cellulose Nanofibril Organization in Plant Cell Walls
- Mathias Nero
- Postdoc,
- KTH
- Co-author(s): Mads Allerup Carlsen, Marianne Liebi, and Tom Willhammar
- Supervisor (PhD-students/postdocs): Anastasia Riazanova
- The mechanical performance of plant cell walls is largely governed by the orientation and hierarchical organization of cellulose nanofibrils. These crystalline polysaccharides form anisotropic, helicoidal, and layered arrangements that enhance stiffness, toughness, and function. A quantitative three-dimensional understanding of fibril orientation is crucial for linking nanoscale organization to macroscopic properties and guiding bio-inspired material design. However, reliable nanoscale characterization of soft biopolymers remains challenging due to their high sensitivity to radiation damage and intrinsically weak scattering from light elements. Here, we present a method based on scanning electron diffraction (SED) for nanoscale mapping of cellulose organization at low electron doses, combined with tailored data analysis. In SED, a nearly parallel electron probe (<10 nm) is rastered across the specimen, recording a diffraction pattern at each probe position, enabling determination of local crystallographic orientations with high spatial resolution. To overcome the inherent two-dimensional limitation of SED, tilt-series acquisition is employed, enabling three-dimensional scanning electron diffraction (3D-SED). This approach allows mapping of fibril orientation in three dimensions and reveals fibrillar chirality. Applying 3D-SED to native birch and oat husk cell walls uncovers their chiral structures. In the layered secondary cell wall of birch, a left-handed S1 layer transitions continuously into a right-handed S2 layer with a larger pitch. In contrast, oat husk exhibits a multilayered cell wall with alternating fibril chirality between layers. These findings demonstrate that 3D-SED offers quantitative insights into the three-dimensional organization of crystalline nanofibrils in complex, electron-beam-sensitive biomaterials.
- Time of presentation: 9.20