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Development of a single cell based biosensor for subcellular on-line monitoring of cell performance for diagnosis and healthcare

Final Report Summary - CELLFORCE (Development of a single cell based biosensor for subcellular on-line monitoring of cell performance for diagnosis and healthcare)

The main objective was to develop a very robust and simple biosensor device for use in an industrial and university environment that enabled online monitoring of cell forces transduced to the substratum. The substratum consists of an array of pillars whose degree of bending relate directly to the forces of the cell in contact with them. The premise of the CELLFORCE sensor was that all parts can be produced solely by industrial processes and exact knowledge regarding cell attachment to the substratum and its functionality at each time point.

During the project much knowledge was gained in each of the scientific fields addressed, including the microstructuring of polymer material and the development of on optical measuring device. Furthermore, topics such as the development of double gene constructs, reporting on the functional state of cells or its shape and attachment as well as of new thermoplastic polymer materials with reduced Young's modulus were also addressed within the CELLFORCE project.

Researchers developed a biosensor based on the on-line monitoring of traction forces that each cell transduces to the substratum surface through the cytoskeleton connected focal adhesion points (FA). FA represented the connecting points between the cell and the material surface. The observation of cellular forces has yielded information about cellular physiology, as well as knowledge on the effects of any substances applied to the cells.

The premises of the CELLFORCE sensor was that by using a soft polymer, shaped to yield a dense array of approximately 5 µm diameter pillars, the action of a force should become apparent by the tilt or deflection of individual pillars. This pillar tilt had to be measured optically. Additional fluorescence markers to label different cellular organelles were observed in parallel. The aim was to establish a long term measurement system for observing cellular motions and associated forces.

Results from the CELLFORCE project led to improved sensory equipment in the field of cell cultivation and detection. New micro structured substrates can now be processed in series; the optical detection system can help the cultivation of cells within the flow chamber of the optical device, etc. In addition, the cell adhesion of the corresponding proteins e.g. talin and vinculin on surfaces are now better understood thanks to the CELLFORCE initiative, an important result that will help in other collaborations.

The CELLFORCE project employed materials from the fields of optics, biocompatibility and cell adhesion properties, moulding and reproductions properties, elasticity/stiffness characteristics, durability. The forces that cell are able to transmit to surfaces were found to be much smaller than expected.

Part of the published data regarding cell forces was based on dried fixed cells without taking the drying process induced shrinkage into account. This meant that the design of the pillar had to be accordingly adapted: smaller diameter of the pillars or increase of the length of the pillars, less stiffer materials. This had consequences for the coating procedure and the analysis software. In addition, based on other reports it must be assumed that cells are able to adapt their forces depending on the stiffness of the substratum making it with current available materials and techniques impossible to define and produce optimal pillar characteristics for a biosensor for industrial applications. Although the final goal, the CELLFORCE biosensor, could only partly be achieved, because of physical, biological and technical limitations the present project must be seen as successful.

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