21. July 2021

The unique device could be used for testing materials for novel types of body implants

The Core Facility Nanobiotechnology at CEITEC Masaryk University in Brno recently completed the installation of a new device. It is the atomic force microscope (AFM) JPK NanoWizard 4XP, used for biomechanical scanning combined with an optical fluorescence microscope. This specialized bio-AFM microscope enables local study of the mechanical properties on samples, ranging from tissues or small organisms up to the individual biomolecules. Standard AFM microscopes are not suitable for working with this type of biological samples. However, the new device is adapted to work with biological samples in physiological conditions and additionally provides a significantly greater range of motion, which enables scientists to also study large and fragmented samples. One can investigate mechanical properties of bone sections, plant parts, but also cells in cell cultures. An important area of ​​application is the study of cell adhesion to new types of materials that are being used for the construction of body implants.

Atomic force microscopy is a microscopic technique used since the late 1980s to image surfaces in three dimensions. With this method, scientists study the adhesion of a material, but also its elasticity or plasticity. The image of the surface is assembled gradually, point by point. This method achieves a very high resolution and can display even individual atoms. The AFM technique can be used not only for imaging, but also for forming structures or for processing of surfaces in the nanometer range. AFM microscopes belong to the group of microscopes working with a scanning probe. The interaction between this probe, which is usually a pyramidal tip, and the surface then allows the creation of a topographic image of the sample and also the measurement of its mechanical properties.

"The best instruments are really able to see individual atoms, but this is especially true for research in materials engineering. If we talk about the so-called bio-AFM microscopy, the resolution for biological samples typically begins at the level of the double-helical structure in the DNA molecule and ends at the level of whole cells, cell clusters and tissues. A new trend is the use of AFM in the so-called nanoindentation, where the microscope probe serves as a nanosensor, applying a precisely controlled force to the sample. This experimental approach then enables the study of mechanical properties, such as adhesiveness, elasticity or plasticity. Thanks to the high accuracy of the AFM microscope, it is possible to monitor these properties at the level of individual biomolecules, but of course it is also possible to increase the sample size up to the tissues or small organisms," explains Jan Přibyl, head of the Core Facility Nanobiotechnology.

The main advantage of this microscope is the extended measuring range. Scientists working with large and fragmented samples have been longing for this feature for a while. The scientific potential of the device is greatly increased by expansion modules FluidFM and NanoIndenter Biosoft. FluidFM is a special part of the AFM microscope, where otherwise a full probe contains a microfluidic channel connected to the pump. Such a system can be compared to a nanopipette with extremely precise control not only in terms of movement but also for targeted force interaction. The nanopipette can then be used to picoinject various solutions into individual cells or to extract extremely small volumes at the level of individual cells. Another interesting application is the study of cell adhesion on surfaces, which is a basic parameter for testing new materials with potential use for implant construction. In this process, the cell is aspirated with a nanopipette and the force required to tear it from the surface is monitored. The FluidFM module can also serve as a 3D nanoprinter.

NanoIndenter BioSoft is a modification of the standard indenter for working with biological and very soft samples. The classic indenter is a device based on the linear ejection of a hard tip, which could be described as a needle with a precisely defined tip. During the extension, the studied material is deformed and its mechanical properties are described during the deformation process. However, Indenter was developed primarily for materials research, to study very hard and rigid materials, such as alloys, ceramics, semiconductors, etc. The BioSoft device is the first of its kind that is suitable for working with very soft samples. It is thus possible to study the mechanical properties of hydrogels, cells in cell cultures, tissues, parts of plants, but also bone sections or bacterial biofilms. The device thus suitably complements the results obtained by AFM nanoindentation.

In addition to standard AFM imaging applicable to a wide range of samples, the new instrument will primarily serve scientists studying the pathophysiology of various diseases through changes in the mechanical properties of cells. An indisputable advantage is the possibility of working under so-called semi-physiological conditions, which are very close to physiological conditions. As part of the installation, the Core Facility Nanobiotechnology also organized a series of three workshops, with the aim to familiarize the scientists with the potential of this unique device.