Yingmin Qu

Mechanical properties study of SW480 cells based on AFM.

Since the invention of the atomic force microscope (AFM), it has been widely applied in biomedicine. One of the most important applications is used as an indenter tool to do the indentation experiment in order to get the mechanical properties of cells. In this paper, SW480 cells were used as the test subjects. Through the analysis of the contact and indentation, Youngs modulus (E), which is an important parameter of cancer cells, has been estimated. Experimental results show that different mechanical models should be chosen to calculate the E in different indentation depths. Here, the E of SW480 cells was (2.5 ± 0.8) KPa at the indentation depth of 99 nm.

AFM-detected apoptosis of hepatocellular carcinoma cells induced by American ginseng root water extract

American ginseng as a common and traditional herbal medicine has been used in cancer treatment for many years. However, the effect of American ginseng on the cancer cell response (i.e. apoptosis) has not been fully understood yet. Previous studies demonstrated that cellular apoptosis was associated with the changes of mechanical and morphological properties. Therefore, in this study, mechanical and morphological characterizations were carried out by both atomic force microscope (AFM) and inverted optical microscope to investigate the apoptosis of hepatocellular carcinoma (SMMC-7721) cells affected by American ginseng root water extract (AGRWE). The results showed that the cells treated with AGRWE exhibited significantly larger surface roughness, height and elastic modulus values than control group. Moreover, those parameters were upregulated under the higher concentration of AGRWE and longer culture time. Consequently, it indicates that the mechanical and morphological properties can be used as the apoptotic characteristics of SMMC-7721 cells. Also, the increased surface roughness and elastic modulus of cells under the AGRWE treatment have shown that the apoptosis of SMMC-7721 cells can be enhanced by AGRWE. This will provide an important implication for hepatocelluar carcinoma treatment and drug development.

Response of MG63 Osteoblast Cells to Surface Modification of Ti-6Al-4V Implant Alloy by Laser Interference Lithography

The response of human osteoblast-like osteosarcoma cells (MG63) to surface modification of Ti-6Al-4V implant alloy was investigated by Laser Interference Lithography (LIL). In this work, laser interference lithography was employed to fabricate the microstructures of grooves, dots and dimples onto the surfaces of Ti-6Al-4V samples. Two and three beam LIL systems were developed to carry out the experiments. The laser treatment resulted in the increases of the roughness and the contact angle of water on the implant alloy surfaces. The proliferation of osteoblasts was analyzed by MTT (3-(4,5-dimethyl- 2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay for the time periods of 4 hours, 2 days, 3 days, and 6 days. The MTT test results demonstrated that the laser treatment surfaces had a positive impact on the proliferation of osteoblast cells after 24 hours. The alloy surface morphology and the morphological changes of MG63 cells cultured on the laser textured Ti-6Al-4V surface were observed by Scanning Electron Microscope (SEM). The SEM results indicated that the osteoblast cells were aligned on grooved surfaces and they were prolonged with the structures. Enzymatic detachment results showed that the 20 µm grooved structures provided the better cell adhesion to the textured Ti-6Al-4V surfaces.

Effect of fullerenol on the morphology features of SW480 cells

Paper discusses the effect of fullerenol on the morphology features of colon cancer SW480 cells. In the work, the changes of morphology features of SW480 cells, treated with three groups of fullerenol concentrations, were studied using atomic force microscopy (AFM) to evaluate their induction of apoptosis in colon cancer cells on the nanoscale. There were 20 single cells of each group used to test and determine the changes of their features in the experiments, including untreated SW480 cells, SW480 cells treated with Img/ml fullerenol and SW480 cells treated with 2mg/ml fullerenol. The experimental results have shown that the untreated and treated SW480 cells have different sizes and shapes. The lengths of the cells were decreased and their heights increased with the increase of the fullerenol dose.

Study of morphological and mechanical features of multinuclear and mononuclear SW480 cells by atomic force microscopy

This article studies the morphological and mechanical features of multinuclear and mononuclear SW480 colon cancer cells by atomic force microscopy to understand their drug‐resistance. The SW480 cells were incubated with the fullerenol concentrations of 1 mg/ml and 2 mg/ml. Morphological and mechanical features including the height, length, width, roughness, adhesion force and Youngs modulus of three multinuclear cell groups and three mononuclear cell groups were imaged and analyzed. It was observed that the features of multinuclear cancer cells and mononuclear cancer cells were significantly different after the treatment with fullerenol. The experiment results indicated that the mononuclear SW480 cells were more sensitive to fullerenol than the multinuclear SW480 cells, and the multinuclear SW480 cells exhibited a stronger drug‐resistance than the mononuclear SW480 cells. This work provides a guideline for the treatments of multinuclear and mononuclear cancer cells with drugs.

Compensation of the magnetic force imaging by scanning directions

It was found that the results of magnetic force microscope (MFM) imaging were different with the probe scanning directions. This paper studied the effect of scanning directions on the MFM imaging, and a method for the distortion compensation was proposed to reduce the errors. In the study, three different scanning directions with the angles of 0°, 45° and 90° were used to measure the magnetic domain structures distributions of magnetic sample. The experimental results have shown that the scanning direction parallel to the magnetic domain structure will cause a minimum phase shift difference and lead to a structure distortion. A method for compensating the distortions was proposed. With this method, the distorted structures were corrected and the effect of scanning directions on the MFM imaging was significantly reduced. This work provides a way for the acquisition of the correct images of magnetic structures using an MFM and the improvement of imaging quality in a wide range of MFM applications.

A method for the mechanical stimulation of living single-cells using a voltage-excited AFM probe

In this paper, we developed a method to drive the oscillation of AFM conductive probe cantilever for stimulating living single cells in liquid with an AC-voltage excitation. We took a copper foil stuck at the bottom of the petri dish as an electrode and the AFM conductive probe was used as both a nano electrode and an actuator to stimulate the living cells when a bias voltage was applied to the electrodes. The voltage and distance between the two electrodes can be adjusted to obtain various required stimulation effects. In the work, the application of electrostatic force and electrolysis for stimulating living cells with bias voltages was analyzed. The experiment results have shown that the method is able to perform controllable stimulation and precise positioning of cells with the AFM The developed system is an efficient stimulation tool for the study of cellular physiological behaviors.

Effect of curing time on cell structures

In this paper, the HL7702 cells were cured with 4% paraformaldehyde for different time durations. The atomic force microscope (AFM) and atomic force acoustic microscope (AFAM) were used to observe the surface and subsurface properties of the cured cells. The structures of the cells were changed with the curing time including the cytoskeleton, the shape, the height and the roughness of the cells. The lamellipodium can be seen for the curing time of 15 minutes with 4% paraformaldehyde. The optimal curing time was 15 minutes. This work provides a method for the study of cured cells in biomedicine.

Effect of liquids on AFM imaging

AFM (atomic force microscope) imaging in liquids is very important in measurement science for bio-applications. This paper discusses the effect of liquids on AFM imaging. In a developed AFM system, a standard 2D grating was used for the study of AFM imaging in different liquids including deionzed water, DMEM (Dulbeccos Modified Eagle Medium) and DMEM with 10% of FBS (Fetal Bovine Serum). AFM images acquired from different liquids were analyzed in terms of the image contrast and standard deviation of the grating period by Matlab. The experimental results have shown clearly the different effects of liquids on AFM imaging. The AFM imaging quality in liquids is a function of different forces acting on the cantilever and is directly related to the physical properties of the liquids.