Investigation of effect of fullerenol on viscoelasticity properties of human hepatocellular carcinoma by AFM-based creep tests

Cellular elasticity is frequently measured to investigate the biomechanical effects of drug treatment, diseases, and aging. In light of the cellular viscosity property exhibited by filament actin networks, this study investigates the viscoelasticity alterations of the human hepatocellular carcinoma (SMMC-7721) cell subjected to fullerenol treatment by means of creep tests realized by atomic force microscopy indentation. An SMMC-7721 cell was first modeled as a sphere and then as a flattened layer with finite thickness. Both Sneddon's solutions and the Dimitriadis model have been modified to adapt to the viscoelastic situation, which are used to fit the same indentation depth-time curves obtained by creep tests. We find that the SMMC-7721 cell's creep behavior is well described by the two modified models and the divergence of parameters determined by the two models is justified. By fullerenol treatment, the SMMC-7721 cell exhibits a significant decrease of elastic modulus and viscosity, which is presumably due to the disruption of actin filaments. This work represents a new attempt to understand the alternation of the viscoelastic properties of cancerous cells under the treatment of fullerenol, which has the significance of comprehensively elucidating the biomechanical effects of anticancer agents (such as fullerenol) on cancer cells.