The SNAP AFM standardization procedure

SNAP is a calibration procedure that allows reliable measurement of Young’s elastic modulus for soft samples, such as living cells, by atomic force microscopy

Following the European COST TD1002 project that we coordinated between 2010 and 2014, a multi-site and multi-machine round-robin study has been developed to improve the quantification of the elastic Young modulus of cells. This study produced a protocol called SNAP (temporarily named Dubrovnik procedure). The essence of the protocol is to improve the calibration of AFM instruments using pre-calibrated cantilevers whose spring constants have been experimentally determined. This allows a better calibration of the photodiode sensitivity. Once the procedure is applied, variability of elasticity measurements dropped to 1% on hydrogels. Below is shown the improve results (on the right) when the protocol was applied on eukaryotic cells MDCK C11. This is typically a joint project where it is difficult to assign a participatory hierarchy. However, the major role of Hans Oberleithner in the development of this action must be emphasized, as well as the driving role of Manfred Radmacher and also of Hermann Schillers in setting up and distributing the samples for the whole group.

Schillers H, Rianna C, Schäpe J, Luque T, Doschke H, Wälte M, Uriarte JJ, Campillo N, Michanetzis GP, Bobrowska J, Dumitru A, Herruzo ET, Bovio S, Parot P, Galluzzi M, Podestà A, Puricelli L, Scheuring S, Missirlis Y, Garcia R, Odorico M, Teulon JM, Lafont F, Lekka M, Rico F, Rigato A, Pellequer J-L, Oberleithner H, Navajas D and Radmacher M (2017) Standardized Nanomechanical Atomic force microscopy Procedure (SNAP) for measuring soft and biological samples. Sci. Rep. 7: 5117.