Standardized Nanomechanical Atomic Force Microscopy Procedure (SNAP) for Measuring Soft and Biological Samples

Hermann Schillers (1) , Carmela Rianna (2) , Jens Schäpe (2) , Tomas Luque (3) , Holger Doschke (2) , Mike Wälte (1) , Juan José Uriarte (3) , Noelia Campillo (3) , Georgios P A Michanetzis (4) , Justyna Bobrowska (5) , Andra Dumitru (6) , Elena T Herruzo (6) , Simone Bovio (7) , Pierre Parot (8) , Massimiliano Galluzzi (9) , Alessandro Podestà (9) , Luca Puricelli (9) , Simon Scheuring (10) , Yannis Missirlis (4) , Ricardo Garcia (6) , Michaël Odorico (11) , Jean-Marie Teulon (12) , Frank Lafont (7) , Malgorzata Lekka (5) , Felix Rico (13) , Annafrancesca Rigato (13) , Jean-Luc Pellequer (12) , Hans Oberleithner (1) , Daniel Navajas (3) , Manfred Radmacher (2)

1 WWU - Westfälische Wilhelms-Universität Münster = University of Münster
2 University of Bremen
3 University of Barcelona
4 University of Patras
5 PAN - Polska Akademia Nauk = Polish Academy of Sciences = Académie polonaise des sciences
6 ICMM - Instituto de Ciencia de Materiales de Madrid
7 Institut Pasteur de Lille
8 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
9 UNIMI - Università degli Studi di Milano = University of Milan
10 Department Radiation Oncology (Weill Cornell Medicine)
11 L2ME - Etude de la Matière en Mode Environnemental
12 IBS - UMR 5075 - Institut de biologie structurale
13 Bio-AFM-Lab - BIO-AFM-LAB Bio Atomic Force Microscopy Laboratory

We present a procedure that allows a reliable determination of the elastic (Young's) modulus of soft samples, including living cells, by atomic force microscopy (AFM). The standardized nanomechanical AFM procedure (SNAP) ensures the precise adjustment of the AFM optical lever system, a prerequisite for all kinds of force spectroscopy methods, to obtain reliable values independent of the instrument, laboratory and operator. Measurements of soft hydrogel samples with a well-defined elastic modulus using different AFMs revealed that the uncertainties in the determination of the deflection sensitivity and subsequently cantilever's spring constant were the main sources of error. SNAP eliminates those errors by calculating the correct deflection sensitivity based on spring constants determined with a vibrometer. The procedure was validated within a large network of European laboratories by measuring the elastic properties of gels and living cells, showing that its application reduces the variability in elastic moduli of hydrogels down to 1%, and increased the consistency of living cells elasticity measurements by a factor of two. The high reproducibility of elasticity measurements provided by SNAP could improve significantly the applicability of cell mechanics as a quantitative marker to discriminate between cell types and conditions.

Domaines: Biologie structurale [q-bio.BM]

Hermann Schillers, Carmela Rianna, Jens Schäpe, Tomas Luque, Holger Doschke, et al.. Standardized Nanomechanical Atomic Force Microscopy Procedure (SNAP) for Measuring Soft and Biological Samples. Scientific Reports, 2017, 7 (1), pp.5117. ⟨10.1038/s41598-017-05383-0⟩. ⟨hal-01575563⟩