Determination of the Elastic Properties of Tomato Fruit Cells with an Atomic Force Microscope

Abstract

Since the mechanical properties of single cells together with the intercellular adhesive properties determine the macro-mechanical properties of plants, a method for evaluation of the cell elastic properties is needed to help explanation of the behavior of fruits and vegetables in handling and food processing. For this purpose, indentation of tomato mesocarp cells with an atomic force microscope was used. The Young's modulus of a cell using the Hertz and Sneddon models, and stiffness were calculated from force-indentation curves. Use of two probes of distinct radius of curvature (20 nm and 10,000nm) showed that the measured elastic properties were significantly affected by tip geometry. The Young's modulus was about 100 kPa ± 35 kPa and 20 kPa ± 14 kPa for the sharper tip and a bead tip, respectively. Moreover, large variability regarding elastic properties (>100%) among cells sampled from the same region in the fruit was observed. We showed that AFM provides the possibility of combining nano-mechanical properties with topography imaging, which could be very useful for the study of structure-related properties of fruits and vegetables at the cellular and sub-cellular scale.

Nanometrology of Biomass for Bioenergy: The Role of Atomic Force Microscopy and Spectroscopy in Plant Cell Characterization

“…Force measurements using AFM (Zdunek and Kurenda, 2013) and derivative technologies such as quantitative force-volume mapping (QFM) (Radmacher et al, 1996) and peak-force (Adamcik et al, 2011) allow nanomechanical mapping with nanometer scale lateral resolution, and measurements of forces down to few piconewtons. These techniques are currently used for mechanical characterization in cell biology (living cells) and structural biology, including testing of cartilage (Heu et al, 2012), bones (Spitzner et al, 2015), soft tissues (Burgert and Keplinger, 2013), and wood (Farahi et al, 2017).…”

Single Cell Wall Nonlinear Mechanics Revealed by a Multiscale Analysis of AFM Force-Indentation Curves

“…Different methods have been designed over the past decades to characterize the single-cell-wall elastic modulus through global compression (7,8) or bending strain (9) experiments. The mechanical properties of single plant cells were also tracked down locally, with nanotipped indentation systems provided by an atomic force microscope (AFM) (10)(11)(12)(13)(14)(15)(16)(17) or by cellular force microscopes (18,19).…”

“…The mechanical characterization of a single plant cell with an AFM cantilever depends on the tip shape. As for animal cells, large spherical indenters are better suited to capture the internal pressure of the cell, whereas sharp conical or pyramidal tips are more appropriate for characterizing the local mechanics of the wall (15,17). This latter tip geometry has been chosen in this work to study single-cell-wall mechanics from Arabidopsis thaliana root calli.…”

Scientific basis of nanotechnology, implications for the food sector and future trends

“…By probing the surface of samples with a nanometrical tip, AFM has been used to probe molecular interactions via force spectroscopy (Morris, Woodward, & Gunning, 2011). Moreover, AFM has been demonstrated as an ideal platform to develop advanced techniques for nanomechanical characterization of samples (Passeri, Rossi, Tamburri, & Terranova, 2013), the potential of which for the analysis of Young's modulus, complex elastic modulus, hardness, tip-sample adhesion force has been only marginally explored in food derived samples (Goode, Bowen, Akhtar, Robbins, & Fryer, 2013;Morton et al, 2003;Scramin et al, 2011;Zdunek & Kurenda, 2013). As an example, Fig.…”