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Biomechanical properties of cells are altered by many diseases. Cancer cell metastasis is related to the properties such as the cell stiffness that influences cell proliferation, differentiation and migration. In this paper, we used an atomic force microscope to analyze the colchicine-induced effects on the mechanical properties of hepatocyte (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture at the nanoscale. The cells were exposed to a solution with a normal dose of colchicine for two, four and six hours. Surface topographic images showed that colchicine decreased the stability of the cytoskeleton. After the same six-hour treatment in a solution with a normal dose of colchicine, the biomechanical properties of HL-7702 cells were almost unchanged. However, the stiffness and the adhesion force of the SMCC-7721 cells were clearly increased (more than twofold of the normal values), especially after four hours. The deformability of SMCC-7721 cancer cells was significantly decreased within the six-hour treatment in the solution with a normal dose of colchicine. Analysis of the biomechanical properties of post-treatment hepatoma cells provided a complementary explanation for the mechanism of action of colchicine on cells at the nanoscale. This method is expected to allow the monitoring of potential metastatic cancer cell changes, thus preventing the emergence and the transmission of disease, and improving the diagnosis of cancer.

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Conductive atomic force microscopy (C-AFM) is a powerful tool used in the microelectronics analysis by applying a certain bias voltage between the conducting probe and the sample and obtaining the electrical information of sample. In this work, the surface morphological information and current images of the lambda DNA (λ DNA) molecules with different distributions were obtained by C-AFM. The 1 and 10 ng μl−1 DNA solutions were dripped onto mica sheets for making randomly distributed DNA and DNA network samples, and another 1 ng μl−1 DNA sample was placed in a DC electric field with a voltage of 2 V before being dried for stretching the DNA sample. The results show that the current flowing through DNA networks was significantly higher than the stretched and random distribution of DNA in the experiment. The I–V curve of DNA networks was obtained by changing the bias voltage of C-AFM from −9 to 9 V. The currents flowing through stretched DNA at different pH values were studied. When the pH was 7, the current was the smallest, and the current was gradually increased as the solution became acidic or alkaline.

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