Implementing The Mechanics Measurement On Cell Membrane By Atomic Force Microscopy

The cell membrane plays a vital role in the every cellular activities and is a selective boundary between intracellular cytoplasm and the extracellular environment.Most of the cellular functions occur at the cell membrane boundary,including the exchange of substance and energy,signal transduction,viral infection and drug targets.Viral infection is a process in which viruses bind to cell membranes and then internalize into cell to further complete the infection.Most of the drug targets are located at the cell membrane boundary.The antigen epitopes of highly specific monoclonal antibody drugs are entirely located at the boundary.Understanding the biomechanical properties of cell membrane boundaries at physiological conditionare essential to elucidate the functions and activities of cell membranes.Herein,the correlative biomechanical properties of Ebola virus and monoclonal antibody drugs at the cell membrane boundary were studied under physiological conditions using force tracing technology,nano-indentation and single molecule force spectroscopy based on atomic force microscopy(AFM).1.The force tracing technique based on AFM was used to analyze the trans-membrane dynamics of single Ebola virus.We quantitatively measured the force and time of trans-membrane transport at single Ebola virus level.The results showed that two different endocytosis states were observed during viral trans-membrane transport.The two states observed in experiments were related to the angle of EboV contacting with cell membrane and the position of the filamentous EboV(with a large length to diameter ratio)attaching to AFM tip.The force of single virions internalization into living cell ranged from 21 to 189 pN with the peak value of 41.8 ± 1.05 pN,and the corresponding duration distributed in the range of 0.17-2.07 s with the peak value of 0.27 ± 0.02 s in the first state.In contrast,the force was 56.2 ± 1.10 pN and the duration was 0.39 ± 0.03 s for the second state.2.The nanoindentation technique based on AFM was used to determine the changes of single-cell mechanical properties before and after the treatment of anticancer drugs.Previous studies suggested that the mechanical properties between cancer cells and normal cells were significantly different.In this work,we quantitatively analyzed the changes of mechanical properties of single cancer cells after the treatment of cetuximab using the AFM based nanoindentation.The Young's modulus value was approximately 6.22 kPa after cetuximab treatment,and this value was significantly higher than that of the control group(3.42 kPa).The results suggested that cetuximab can effectually decrease the migration and proliferation of cancer cells by enhancing their rigidity while efficiently achieving anti-tumor effect.3.The meaurement of the interaction force between monoclonal antibody anticancer drug and cell membrane surface receptors by single molecule force spectroscopy.Cetuximab,monoclonal antibody anticancer drug,had a stronger binding efficacy to epidermal growth factor receptor(EGFR)than that of epidermal growth factor(EGF).The binding force between cetuxime and EGFR was similar to that between epidermal growth factor(EGF)and EGFR,but the binding probability was higher than of that between EGF and EGFR.It is concluded that cetuximab has a strong competitive binding ability at the single molecule level at the cell membrane boundary.