Subsurface phase imaging of tapping-mode atomic force microscopy at phase resonance.

The phase image of tapping-mode atomic force microscopy (TM-AFM) contains energy dissipation, which is related to the sample information on the physical properties such as the sample Young's modulus, adhesion, surface morphology and subsurface morphology. When TM-AFM is used for sample measurement, the frequency near the first resonance peak of probe is usually selected to drive the probe vibration. When the probe vibration is driven by the frequency, the probe has a high amplitude sensitivity, but the phase sensitivity is relatively low. In this paper, the frequency at the probe phase resonance peak was selected for driving the probe vibration to measure the sample, which improved the image resolution. Phase imaging was performed on three uniform photoresist samples with different thicknesses and the same structure. When the scanning parameters were fixed and the probe setpoint value was changed alone, it was found that with the decrease of setpoint value the horizontal resolution of the phase subsurface image was decreased, and the depth sensitivity was increased first and then decreased. The result shows that TM-AFM working at the phase resonance peak can better realise the subsurface imaging of samples at different depths. Phase subsurface imaging at the resonance can be used to quantitatively obtain subsurface phase images of different depths.

Effects of Tricholoma matsutake (Agaricomycetes) Extracts on Promoting Proliferation of HaCaT Cells and Accelerating Mice Wound Healing.

Tricholoma matsutake is popular in Asian countries because of its edibility and medicinal use. T. matsutake is a precious natural medicinal fungus, and it is widely used in food and biological products. This study aimed to explore the mechanism of T. matsutake on promoting proliferation of human immortalized keratinocyte (HaCaT) cells and accelerating wound healing in mice. The MTT assay was used to test the effects of three different T. matsutake extracts (0, 62.5, 125, 250, 500, and 1000 µg/mL) on HaCaT cell viability. HaCaT cells were treated with the three T. matsutake extracts (100, 500 µg/mL) and morphological and biophysical properties were detected by atomic force microscopy with JPK data processing. Western blot analysis detected Notch signaling pathways of HaCaT cells treated with 50% ethanol extract of T. matsutake (50%T) for 24 h (100, 500 and 1000 µg/mL). Mouse wounds were treated with 50%T for 15 days. Wound healing effects were observed on the back skin of mice at different times. The quality of wound healing was estimated by histological staining (hematoxylin and eosin and Masson's trichrome). All data were counted by GraphPad Prism 5 software. The increased concentration of T. matsutake remarkably promoted HaCaT cell proliferation. The Young's modulus of HaCaT cells showed the biggest increase from 1.73 ± 0.13 kPa (0 µg/mL) to 4.57 ± 0.16 kPa (500 µg/mL) in the 50%T group. The Notch1/Jagged1 pathways were upregulated with an increase in concentration (0, 100, 500, and 1000 µg/mL). Moreover, compared with the negative and positive control groups, T. matsutake promoted wound healing in mice by epidermal regeneration, subepidermal tissue formation, and collagen deposition. The results showed that T. matsutake promotes not only proliferation of HaCaT cells but also wound healing in mice.

Application of atomic force microscope in diagnosis of single cancer cells.

Changes in mechanical properties of cells are closely related to a variety of diseases. As an advanced technology on the micro/nano scale, atomic force microscopy is the most suitable tool for information acquisition of living cells in human body fluids. AFMs are able to measure and characterize the mechanical properties of cells which can be used as effective markers to distinguish between different cell types and cells in different states (benign or cancerous). Therefore, they can be employed to obtain additional information to that obtained via the traditional biochemistry methods for better identifying and diagnosing cancer cells for humans, proposing better treatment methods and prognosis, and unravelling the pathogenesis of the disease. In this report, we review the use of AFMs in cancerous tissues, organs, and cancer cells cultured in vitro to obtain cellular mechanical properties, demonstrate and summarize the results of AFMs in cancer biology, and look forward to possible future applications and the direction of development.

Modeling and correction of image pixel hysteresis in atomic force microscopy.

In an atomic force microscope (AFM) system, the measurement accuracy in the scan images is determined by the displacement accuracy of piezo scanner. The hysteresis model of piezo scanner displacement is complex and difficult to correct, which is the main reason why the output displacement of the piezo scanner does not have high precision. In this study, an image pixel hysteresis model of the piezo scanner displacement in the AFM system was established. An AFM was used to scan a two-dimensional (2D) grating in the 0 ° and 90 ° directions and a polynomial fitting method was employed to obtain the image pixel hysteresis model parameters of the piezo scanner displacement in the X-direction and Y-direction. The image pixel hysteresis model was applied to correct the AFM scan image of regular octagons. The results showed that the relative measurement error in the X-direction was decreased from 12.47% to 0.52% after the correction and that in the Y-direction decreased from 28.57% to 0.35%. The image pixel hysteresis model can be applied in the post-processing software of a commercial AFM system. The model solves the hysteresis problem of the AFM system and improves the measuring accuracy of AFM in 2 degrees of freedom (2 DOF).

Effect of extract from ginseng rust rot on the inhibition of human hepatocellular carcinoma cells in vitro.

Hepatocellular carcinoma (HCC) is one of major leading causes of cancer death worldwide. As a traditional medicine, the anti-cancer function of ginseng is being growingly recognized and investigated. However, the effect of ginseng rust rot on human HCC is unknown yet. In this study, the HCC cells were treated with different parts of mountain cultivated ginseng rust rot and compared with human normal liver cells. The morphology, survival rate and ß-actin expression of the cells were changed by introducing the ginseng epidermis during the incubation process. Notably, the results reveal that the ginseng epidermis can induce apoptosis by altering the morphologies of cells, indicating the practical implication for the HCC treatment and drug development.