AFM microrheology - methodological advances and the role of fluidization in the diagnosis of civilization diseases

Monitoring changes in viscoelastic properties at both the single-cell and tissue level may serve as a tool not only for medical diagnostics but also for monitoring and assessing the effectiveness of applied therapies. However, the introduction of biomechanical–rheological markers into clinical practice requires their thorough understanding and correlation with specific pathological conditions. Atomic force microscopy (AFM) enables the characterization of the viscoelastic properties of cells and tissues based on oscillatory and relaxation measurements. These methods allow for a quantitative analysis of the elastic and viscous components of sample viscoelasticity by determining parameters such as the apparent Young’s modulus (E), the elastic component of the shear modulus G* (i.e., the storage modulus, G′), the viscous component of the shear modulus G* (i.e., the loss modulus, G″), as well as the loss factor (G″/G′). Moreover, time- and frequency-dependent analyses make it possible to study the process of material fluidization, quantitatively described by the transition frequency (fT) or the Deborah number, which provide insights into the structure of the sample under study. This, in turn, enables a quantitative description of the relaxation dynamics of biopolymer networks forming the cellular cytoskeleton. The obtained results provide a comprehensive picture of the mechano-rheological properties of biological samples, which, when correlated with pathological states, open new perspectives for diagnostic applications and the evaluation of the effectiveness of novel therapeutic strategies.