Characterization of AFM for elasticity analysis of biological samples: Application to diagnosis

Cytomorphological- and immunofluorescence-based methods are currently use for the diagnosis of malignant human tumors. However, morphological overlaps between tumor and normal cell types frequently occur. Recently, a change in cell elasticity of tissues has been recognized as a marker of tissues metastatic potential. Atomic force Microscope (AFM) can quantitatively distinguish cancer and normal cells by measuring the cell elastic modulus when operating in Force Spectroscopy mode. Thus, AFM as elasticity sensor can be a novel diagnostic method for cancer detection. With the broader aim to translate this novel method into clinical application, a preliminary metrological characterization of the AFM sensor is presented in this work. The sensor is characterized in the interested elasticity range, indenting in vitro models of biological materials with elasticity of 5 MPa-50 kPa. Measurement repeatability of 10 % is obtained in a suitable fit range with an indentation speed comparable with the sample viscous relaxation time (1 um/s). Opportunities of improvement for measurement reproducibility are discussed by analyzing surfaces images and the behavior of elasticity versus indentation depths.