Interrogation of drug effects on HeLa cells by exploiting new AFM mechanical biomarkers

Abstract

New mechanical biomarkers were discovered and used to investigate drug effects on HeLa cells. HeLa cells were measured using advanced atomic force microscopy (AFM) techniques before and after treatment with an anticancer drug (docetaxel, a microtubule polymerizer) and the biomechanical properties of cells were analyzed using theoretical models. The biomechanical results show that the length of the surface brush, the factor of viscosity, and the adhesion work of untreated HeLa cells reduced from 920 nm, 0.72 and 4.12 × 10⁻¹⁶ N m to 673 nm, 0.52 and 5.37 × 10⁻¹⁷ N m for treated cells, respectively. In order to reveal the underlying mechanisms of these changes, transmission electron microscopy (TEM) and western blotting assays were employed to characterize structural changes of the cells. Compared to the untreated cells, TEM images confirmed a thinner brush layer on the surface of treated cells while the western blotting of tubulin extracted from the cells indicated an increased microtubule concentration for the treated cells. These changes are consistent with previous studies on the influence of docetaxel on cells. Based on the above results, we conclude that docetaxel can lead to an increased microtubule network in HeLa cells, a thinner brush layer on HeLa cell surfaces and that the length of surface brush, the factor of viscosity, and the adhesion work can be exploited as effective mechanical biomarkers to evaluate drug effects on HeLa cells. This work demonstrates a new AFM-based technique that can be exploited to assess drug action on cells and is promising for the application of drug screening.