Regensburg 2016 – scientific programme

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BP: Fachverband Biologische Physik

BP 2: Physics of Cancer

BP 2.4: Talk

Monday, March 7, 2016, 10:30–10:45, H43

Comparison of the visco-elastic properties of cancer and normal cells by step-response AFM — •Carmela Rianna, Holger Doschke, Jens Schäpe, and Manfred Radmacher — Institute of Biophysics, University of Bremen, Germany

We have measured the visco-elastic creep response of cancer cells on different stiffness polyacrylamide gels and compared it with normal cells of the same type. In conventional force indentation curves the viscous and elastic properties cannot be measured separately. So, these data are usually only analyzed in terms of elastic response, even though the response of the cell to a moving AFM tip is viscous and elastic at the same time. Applying a force step in contact and recording the creep relaxation of the cell allows separating the viscous and elastic response independently. This can be converted in the storage and loss modulus as is usually done in soft matter rheology. We have cultured cells on three different substrates: polyacrylamide gels of 5 kPa and 50 kPa, respectively, and "infinitely" stiff Petri dishes. Normal cells showed an increase of the storage modulus from 1 kPa, to 1.5 kPa to 2.2 kPa with increasing sample stiffness. Whereas cancer cells showed a storage modulus around 1.2 kPa, more or less independent of sample stiffness. The loss modulus was around 400 Pas for cancer cells, where normal cells showed an increase from 250 Pas, to 600 Pas and to 700 Pas with increasing stiffness. There is a large difference in adaption of cancer and normal cells to the substrate stiffness. Whereas normal cells sense the softness of the substrate and adapt to it, cancer cells do not change their visco-elastic properties according to it.