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.

Facile fabrication of micropattern surfaces with controlled wettability on PDMS-modified fiber membranes for cell patterning.

Various cell culture substrates have been developed for cell patterning to control cell distributions and orientations in tissue engineering, drug screening and regenerative medicine. In this study, a preparation method of modified fiber membranes was applied in the field of cell patterning, and the obtained fiber membranes guided the cell distributions and orientations flexibly. The aligned electrospinning fiber membranes were dip-coated with polydimethylsiloxane (PDMS) to improve the stability of wettability, and then it was treated with oxygen plasma with a photomask to obtain a hydrophilic-hydrophobic surface micropattern. The morphologies, wettabilities and chemical structures of the membranes were analyzed by using a scanning electron microscope (SEM), drop shape analysis instrument, energy dispersive spectrometer (EDS) and Fourier transform infrared (FTIR) spectrometer. The L929 cells were cultured on the obtained membranes to observe the controlled cell distributions and orientations by using a SEM and fluorescence microscope. The results indicate that the treated membranes have the ability to control both cell distributions and orientations simultaneously. This method offers a novel approach to develop cell culture substrates for cell patterning in tissue engineering.

Bi-layered disulfiram-loaded fiber membranes with antibacterial properties for wound dressing.

In this study, the bi-layered disulfiram-loaded fiber membranes with the antibacterial activity and different surface wettabilities are prepared using electrospinning technology. In the application of wound dressing, the hydrophilic surface of fiber membranes is beneficial for cell adhesion and drug release to heal the wound. Meanwhile, the outside hydrophobic surface is able to block water penetration to reduce the probability of wound infection. The obtained bi-layered drug-loaded fiber membranes are composed of polyvinylidene fluoride (PVDF) bottom surface and disulfiram (DSF)/polylactic acid (PLA) top surface. To modify the top surface wettability, the oxygen plasma modification of bi-layered membranes was carried out. The morphology, wettability, and chemical compositions of bi-layered drug-loaded fiber membranes were analyzed using the scanning electronic microscope (SEM), drop shape analysis instrument, X-ray diffractometer (XRD), and X-ray photoelectron spectrometer (XPS). The bi-layered disulfiram-loaded membranes showed the potent antibacterial activity in vitro against both Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). It was found that the bi-layered membranes had good biocompatibility with L929 cells. Thus, the obtained bi-layered disulfiram-loaded fiber membranes are suitable for wound dressing application.

The influence of different liquid environments on the atomic force microscopy detection of living bEnd.3 cells.

Atomic force microscopy (AFM) is one of the most important tools in the field of biomedical science, and it can be used to perform the high-resolution three-dimensional imaging of samples in liquid environments to obtain their physical properties (such as surface potentials and mechanical properties). The influence of the liquid environment on the image quality of the sample and the detection results cannot be ignored. In this work, quantitative imaging (QI) mode AFM imaging and mechanical detection were performed on mouse brain microvascular endothelial (bEnd.3) cells in different liquid environments. The gray-level variance product (SMD2) function was used to evaluate the imaging quality of the cells in liquids with different physical properties, and the variations in cell mechanical properties were quantitatively analyzed. An AFM detection liquid containing less ions and organics compared with the traditional culture medium, which is beneficial for improving the imaging quality, is introduced, and it shows similar mechanical detection results within 3 h. This can greatly reduce the detection costs and could have positive significance in the field of AFM living-cell detection.

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).

Specific expression of osteopontin and S100A6 in hepatocellular carcinoma.

BACKGROUND: Our aim was to identify differential expression of genes in hepatocellular carcinoma (HCC) with the ultimate goal of discovering novel diagnostic and therapeutic targets. METHODS: We examined differences in gene expression between HCC and noncancerous liver tissue using a cDNA array with probes for 15,843 genes/clones. Two genes, osteopontin (OPN) and S100A6, were found to be >10-fold differentially expressed, and were selected for further immunohistochemical staining in 51 HCC and 10 nonmalignant liver specimens. The relation between OPN and S100A6 alterations and various clinicopathologic parameters was also evaluated. RESULTS: We found a total of 219 genes that were differentially expressed >3-fold. Of these, 109 were upregulated and 110 downregulated. Within this group, 123 genes, including 59 upregulated and 64 downregulated, had been identified previously. These known genes were mainly involved in cell migration, cytoskeleton dynamics, the signaling pathway and cell cycle, and metabolism. OPN expression and S100A6 expression were seen in 26 of 51 (51.0 %) and 16 of 51 (31.4 %) HCC samples, respectively. More importantly, proteins coded by these genes were not found in any noncancerous liver specimen by immunohistochemical analysis. Expression of these genes correlated with poor differentiation (OPN: P = .013; S100A6: P = .008). CONCLUSION: OPN, a secreted phosphoprotein that has been increasingly implicated in the progression and metastasis of cancer, and S100A6, a member of the S100 protein family that can perform cell proliferation, differentiation, migration, and cytoskeletal dynamics, may be promising diagnostic markers and therapeutic targets for HCC. In addition, the results encourage future studies involving the roles of these proteins in the development and progression of this cancer.

A crucial role for dendritic cell (DC) IL-10 in inhibiting successful DC-based immunotherapy: superior antitumor immunity against hepatocellular carcinoma evoked by DC devoid of IL-10.

The dendritic cell (DC)-based tumor immunotherapy has been a new promise of cure for cancer patients, but animal studies and clinical trials have thus far only shown limited success, especially in treating established tumors. Certain immunosuppressive mechanisms triggered by tumor cells or the derivatives are believed to be a major obstacle. We studied the role of DC-derived IL-10 and its negative impact on vaccine efficacy in mouse models. Liver tumor cells were injected via the portal vein, giving rise to disseminated intrahepatic tumors, or s.c. to form solid but extrahepatic tumors. Bone marrow-derived DCs were generated from normal or IL-10-deficient mice and used as the vector to deliver tumor Ags. We demonstrate here that DCs devoid of IL-10, a potent immunosuppressive cytokine, are superior over conventional DCs in triggering antitumor immunity. The IL-10(-/-)DCs were highly immunogenic, expressed enhanced levels of surface MHC class II molecules, and secreted increased amounts of Th1-related cytokines. By inducing tumor-specific killing and through the establishment of immunological memory, the vaccines delivered by IL-10(-/-)DCs could evoke strong therapeutic and protective immunity against hepatocellular carcinoma in the mouse models. These findings will have great clinical impact once being translated into the treatment of malignant, and potentially infectious, diseases in humans.