1
|
Mendová K, Otáhal M, Drab M, Daniel M. Size Matters: Rethinking Hertz Model Interpretation for Cell Mechanics Using AFM. Int J Mol Sci 2024; 25:7186. [PMID: 39000293 PMCID: PMC11241038 DOI: 10.3390/ijms25137186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Revised: 06/17/2024] [Accepted: 06/25/2024] [Indexed: 07/16/2024] Open
Abstract
Cell mechanics are a biophysical indicator of cell state, such as cancer metastasis, leukocyte activation, and cell cycle progression. Atomic force microscopy (AFM) is a widely used technique to measure cell mechanics, where the Young modulus of a cell is usually derived from the Hertz contact model. However, the Hertz model assumes that the cell is an elastic, isotropic, and homogeneous material and that the indentation is small compared to the cell size. These assumptions neglect the effects of the cytoskeleton, cell size and shape, and cell environment on cell deformation. In this study, we investigated the influence of cell size on the estimated Young's modulus using liposomes as cell models. Liposomes were prepared with different sizes and filled with phosphate buffered saline (PBS) or hyaluronic acid (HA) to mimic the cytoplasm. AFM was used to obtain the force indentation curves and fit them to the Hertz model. We found that the larger the liposome, the lower the estimated Young's modulus for both PBS-filled and HA-filled liposomes. This suggests that the Young modulus obtained from the Hertz model is not only a property of the cell material but also depends on the cell dimensions. Therefore, when comparing or interpreting cell mechanics using the Hertz model, it is essential to account for cell size.
Collapse
Affiliation(s)
- Katarína Mendová
- Department of Mechanics, Biomechanics and Mechatronics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 16000 Prague, Czech Republic;
| | - Martin Otáhal
- Department of Natural Sciences, Faculty of Biomedical Engineering, Czech Technical University in Prague, Náměstí Sítná 3105, 27201 Kladno, Czech Republic;
| | - Mitja Drab
- Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, 1000 Ljubljana, Slovenia;
| | - Matej Daniel
- Department of Mechanics, Biomechanics and Mechatronics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 16000 Prague, Czech Republic;
| |
Collapse
|
2
|
Schrader M, Schrinner K, Polomsky L, Ivanov D, Kampen I, Schilde C, Krull R, Kwade A. Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions. Front Bioeng Biotechnol 2023; 11:1254136. [PMID: 37731767 PMCID: PMC10507416 DOI: 10.3389/fbioe.2023.1254136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 08/08/2023] [Indexed: 09/22/2023] Open
Abstract
In biotechnological processes, filamentous microorganisms are known for their broad product spectrum and complex cellular morphology. Product formation and cellular morphology are often closely linked, requiring a well-defined level of mechanical stress to achieve high product concentrations. Macroparticles were added to shake flask cultures of the filamentous actinomycete Lentzea aerocolonigenes to find these optimal cultivation conditions. However, there is currently no model concept for the dependence of the strength and frequency of the bead-induced stress on the process parameters. Therefore, shake flask simulations were performed for combinations of bead size, bead concentration, bead density and shaking frequency. Contact analysis showed that the highest shear stresses were caused by bead-bottom contacts. Based on this, a newly generated characteristic parameter, the stress area ratio (SAR), was defined, which relates the bead wall shear and normal stresses to the total shear area. Comparison of the SAR with previous cultivation results revealed an optimum pattern for product concentration and mean product-to-biomass related yield coefficient. Thus, this model is a suitable tool for future optimization, comparison and scaling up of shear-sensitive microorganism cultivation. Finally, the simulation results were validated using high-speed recordings of the bead motion on the bottom of the shake flask.
Collapse
Affiliation(s)
- Marcel Schrader
- Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Kathrin Schrinner
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
- Institute of Biochemical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Laura Polomsky
- Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dimitri Ivanov
- Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ingo Kampen
- Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Carsten Schilde
- Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Rainer Krull
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
- Institute of Biochemical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| | - Arno Kwade
- Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany
- Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany
| |
Collapse
|
3
|
Overbeck A, Michel S, Kampen I, Kwade A. Temperature influence on the compression and breakage behaviour of yeast cells. Lett Appl Microbiol 2023; 76:ovad089. [PMID: 37528062 DOI: 10.1093/lambio/ovad089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 07/13/2023] [Accepted: 07/31/2023] [Indexed: 08/03/2023]
Abstract
Industrial biotechnology uses microbial cells to produce a wide range of products. While the genetic and molecular properties of these organisms are well understood, less is known about their mechanical properties. Previous work has established a test procedure for single yeast cells using a nanoindentation instrument equipped with a flat-punch probe, which allows single cells (Saccharomyces cerevisiae) to be compressed between two parallel surfaces. The resulting force-displacement curves clearly showed the bursting of the cells and were used to determine characteristics such as burst force and burst energy. Other studies have investigated the influence of growth conditions and measurement conditions on the mechanical characteristics. The recent study examined the mechanical characteristics according to the temperature during compression. Temperature from 0°C to 25°C has no significant effect on the micromechanical properties. Increasing the temperature up to 35°C causes a reduction in the strength of the cells. At even higher temperatures, up to 50°C, the burst force and burst energy increase significantly. A deformation geometry model was used to calculate the cell wall tensile strength as a function of temperature. The results of these studies may facilitate the identification of efficient conditions for cell disruption and product recovery in downstream biotechnological processes.
Collapse
Affiliation(s)
- Achim Overbeck
- Institute for Particle Technology, Technische Universität Braunschweig, Volkmaroder Straße 5, D-38104 Braunschweig, Germany
| | - Stephanie Michel
- Institute for Particle Technology, Technische Universität Braunschweig, Volkmaroder Straße 5, D-38104 Braunschweig, Germany
| | - Ingo Kampen
- Institute for Particle Technology, Technische Universität Braunschweig, Volkmaroder Straße 5, D-38104 Braunschweig, Germany
| | - Arno Kwade
- Institute for Particle Technology, Technische Universität Braunschweig, Volkmaroder Straße 5, D-38104 Braunschweig, Germany
| |
Collapse
|