New AFM techniques for analysing mechanical properties of plant cell walls

Researchers at the ARC Centre of Excellence in Plant Cell Walls have developed two new AFM techniques for assessing mechanical properties of plant cell walls and interactive forces between cellulose fibres.

Schematic diagram of indentation experiments using Lolium multiflorum cells confined within PDMS microwells. The zoomed-in sketch represents the complex layered structure of the cell surface, where the multi-regime nature of the elastic response originates.
Schematic diagram of indentation experiments using Lolium multiflorum cells confined within PDMS microwells. The zoomed-in sketch represents the complex layered structure of the cell surface, where the multi-regime nature of the elastic response originates.

Professor Jason Stokes’ research group at the Australian Research Council Centre of Excellence in Plant Cell Walls are investigating how plant cell walls respond to mechanical stress and how structure at different length scales influences properties and utilisation of cell walls in diverse applications. As the largest source of renewable carbon, plant cell walls have a critical future role in providing transport fuels, raw materials for industrial processes, food security, and functional foods (including dietary fibres) to improve human health.

Determining the mechanical properties of plant cell walls can lead to the development of new cellulose-based materials and foods with optimised digestive properties. With technical support provided by ANFF-Q Professional Officer Dr Kinnari Shelat, the research team used the atomic force microscopy (AFM) facilities at ANFF-Q to develop two new techniques for assessing these properties: the multi-regime nanoindentation analysis technique and the ‘dip and drag’ AFM technique.

The multi-regime nanoindentation analysis allows researchers to probe cell wall deformations at different scales, gather structural information, and identify weak and tough spots within the wall. Indeed, the failure of the wall may be due to the presence of such weak spots rather than the overall toughness of the wall.

The ‘dip and drag’ AFM technique gives information about the interactive forces between cellulose fibres, which tells researchers how the chemistry of different wall components may impact the strength of the links and therefore determine the toughness of the wall.

“The ANFF-Q is enabled to combine the need for AFM equipment, as well as the use of micro-fabrication facilities … We use a number of AFM techniques and instruments, including JPK’s NanoWizard, Asylum Research’s Cypher, and MFP-3D … We are fully utilising the power of combining AFM with other imaging techniques such as CLSM, SEM and TEM to ascertain complex properties of plant walls,” said Dr Gleb Yakubov, a postdoctoral researcher with the team.

These techniques will pave the way for future studies on food systems aimed at understanding the relationship between cell wall composition and microstructure, which ultimately determines the fate of foods within the digestive system. The team aims to uncover the key design rules that will enable the development of foods—both through food processing technologies and through agricultural means—with optimum breakdown patterns. Ultimately, this will promote healthier dietary choices and enhance the nutritional value of common foods.

 

A dual illumination (bright-field and reflected light) optical micrograph of a L. multiflorum cell (b) confined within a PDMS micro-well (a). An AFM cantilever (d) is positioned above the cell so that the tip (e) is positioned approximately above the apex of the cell. The cell wall (c) can be clearly visualised as a shell surrounding the cell. Credit: Dr Gleb Yakubov.
A dual illumination (bright-field and reflected light) optical micrograph of a L. multiflorum cell (b) confined within a PDMS micro-well (a). An AFM cantilever (d) is positioned above the cell so that the tip (e) is positioned approximately above the apex of the cell. The cell wall (c) can be clearly visualised as a shell surrounding the cell. Credit: Dr Gleb Yakubov.