Micromechanical Analysis of Biological Cell Membranes

By AZoNano.com Staff Writers

Topics Covered

Introduction
Experimental Setup
Measurement
Results
Conclusion
About FemtoTools

Introduction

A trend from qualitative analyses of organisms as whole and quantitative observations of their smallest subunit, for instance, the single cell, can be witnessed in several biological research fields. As the physiological functions of biological samples are often closely linked to their mechanical properties, a new field called mechanobiology has emerged.

This trend increases demand for high precision microforce sensing equipment which facilitates quantitative micromechanical testing of biological samples immersed in liquids.

Characterization of biomembranes, which separate the biological structures from their immediate surroundings, is often required in the analysis of the behavior and functions of those structures. Biomembranes are of different types, for instance, the zona pellucida (ZP) is an extracellular biomembrane enveloping an oocyte.

To gain insight into the mechanical properties of mouse ZP and the differences in the mechanical properties of ZP prior to and after fertilization, biomembrane force sensing is performed on mouse oocytes and embryos. The results provide proof for protein cross-linking that biologists have put forward as the mechanism through which ZP hardening takes place.

Experimental Setup

During the micromechanical testing of samples immersed in a liquid, it is not possible to observe the sample from above because of the diffraction of the air-liquid interface. The use of a FT-FS1000 Mechanical Probe from FemtoTools, in conjunction with a high-resolution, inverted microscope, as shown in Figure 1, enables the quantitative micromechanical testing of samples submerged in liquids.

Figure 1. FT-FS1000 Mechanical Probe integrated into an inverted microscope

The combination of a FT-FS1000 Mechanical Probe and a FT-S Microforce Sensing Probe, which is shown in Figure 2, is employed for the micromechanical analysis of the cell membrane of mouse oocytes/embryos. A standard injection pipette tip is attached to the microforce sensing probe utilizing UV curable glue. It is possible to directly perform the pipette attachment through the use of the FT-FS1000 Mechanical Probe, which is delivering a high positioning resolution and force feedback in the event of the gluing task. This facilitates the mounting f the pipette without causing damage to the sensitive microforce sensing probe.

Figure 2. FT-S Microforce Sensing Probe

A holding pipette is used to keep the mouse oocytes/embryos in place. The microforce sensing probe and the holding pipette tip are aligned horizontally. This setup in conjunction with an inverted microscope enables the simultaneous visualization of the sample and the high-resolution micromechanical investigation.

Measurement

Figure 3. Mechanical investigation of the ZP of a mouse oocyte

For the measurement of the mechanical properties of the cell membrane of oocytes/embryos and their change subsequent to the fertilization of the oocytes (become embryos), it is necessary to precisely align them into the optical path of the microscope and versus each other. Once aligned, the FT-WFS02 Micromechanical Testing software is used to carry out fully automated micromechanical characterization. The measurement process involves the mechanical deformation of the ZP until it gets punctured to measure the applied force and deformation.

Results

The mechanical testing of the ZP of mouse oocyte/embryo has concluded that embryo membranes withstand much larger deformations when compared to oocyte membranes before being punctured. The forces required to puncture embryo membranes are nearly two times more than the forces for oocyte membranes, as illustrated in Figure 4. These results quantitatively describe the mechanical property differences caused by mouse ZP hardening.

Figure 4. Results of the mechanical investigation of the ZP of a mouse oocyte

Conclusion

This experiment has important implications for reproductive biologists who work with in vitro fertilization and for biologists developing transgenic organisms for biological research studies. The experiment results provide proof for protein cross-linking that biologists have suggested as the mechanism through which ZP hardening takes place.

About FemtoTools

FemtoTools is a Swiss high-tech company that offers award-winning, ultra high-precision instruments for mechanical testing and robotic handling in the micro- and nanodomains. This new generation of instruments meets the challenging requirements of semiconductor technology microsystem development, materials science, micromedicine and biotechnology.

FemtoTools’ microrobotic handling and measurement instruments feature highly sensitive microforce sensing probes and force sensing microgrippers that are the result of a specially developed microelectromechanical system (MEMS)-based manufacturing process. The unmatched sensitivity and accuracy of our innovative systems redefines the standards for true quantitative investigations in the micro- and nanodomains.

FemtoTools’ easy-to-use microrobotic handling and measurement instruments have exceeded customer’s expectations and create exciting new possibilities, as demonstrated by numerous recent scientific advancements that have used our instruments.

This information has been sourced, reviewed and adapted from materials provided by FemtoTools.

For more information on this source, please visit FemtoTools.

Date Added: Jun 29, 2013 | Updated: Aug 16, 2013
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