Probing the Adhesion of Hepatocellular Carcinoma HepG2 and SK‐Hep‐1 Cells

Carcinoma cell differentiation stage is an important indicator of cell behavior. For example, cell mobility is much higher for poorly‐differentiated hepatocellular carcinoma SK‐Hep‐1 cells than for well‐differentiated HepG2 cells. In this study, we have cultured HepG2 and SK‐Hep‐1 cells on chemically patterned polydimethylsiloxane (PDMS) substrates to observe differences in the adhesion properties and cell structure that occur due to the patterns. Both cell lines showed a preference for the hydrophobic regions on the patterned PDMS surface with SK‐Hep‐1 cells achieving a higher density than HepG2 for the same cell‐count solutions. Further, SK‐Hep‐1 cells adopted the square or hexagonal shape of the surface patterns while HepG2 cells maintained their more rounded shape. AFM force measurement arrays were also performed on the cell surfaces to measure and map adhesion values between the tip and cell surface membrane. These results demonstrate that, in addition to cell shape and size, adhesion expression in hepatocellular carcinoma cells is differentiation stage dependent. Further, the ability of the SK‐Hep‐1 cells to adopt the shape of the substrate pattern indicates they are more structurally labile, which may contribute to their higher mobility.     

Ruptured conjugated polymer thin films formed during spin coating

The formation of ruptured poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenyl vinylene] (MEH–PPV) thin films coated from undried tetrahydrofuran (THF) solutions was investigated. Because of the incompatibility of water and MEH–PPV, the polymer films coated from THF/water solutions showed a ruptured film structure. In the photoluminescence (PL) spectra of the polymer thin films, the ruptured polymer films showed a redshifted emission in comparison with continuous polymer thin films. According to a comparison of the PL spectra of polymer solutions and films, MEH–PPV in THF showed a coil–cylinder transition during precipitation from solution. Because of the incompatibility of water and MEH–PPV, an increase in the water content could increase the ratio of polymer chains in the cylinder conformation, resulting in a redshifted emission for the films. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 79–84, 2006     

Analysis of cysteine glutathionylation in hemoglobin of gastric cancer patients using nanoflow liquid chromatography/triple‐stage mass spectrometry

Glutathione is an intracellular antioxidant capable of scavenging free radicals and detoxifying electrophiles from endogenous and exogenous sources via the free thiol group. Post‐translational glutathionylation at cysteine residues of proteins can affect the structure and cause a functional change of proteins. Protein glutathionylation has been proven to reflect the cellular redox status. Our previous report indicates that the levels of glutathionylation in hemoglobin from peripheral blood of smokers are significantly higher than in nonsmokers. In this study, a nanoflow liquid chromatography/nanospray ionization triple‐stage mass spectrometric (nanoLC/NSI‐MS³) method with a linear ion trap mass spectrometer was employed to quantify glutathionylated peptides in the trypsin digests of hemoglobin from gastric cancer patients. We compare the extent of glutathionylation in hemoglobin from nonsmoking gastric cancer patients with that from nonsmoking healthy adults. Using a carboxymethylated peptide as the reference peptide, the relative quantification of each glutathionylated peptide was measured as the peak area ratio of the modified peptide versus the sum of the peak areas of the modified and the carboxymethylated parent peptide in the selected reaction monitoring chromatograms. Using this method, we found that the extents of glutathionylation at Cys‐104 of the α‐globin and Cys‐93 of β‐globulin hemoglobin from 10 gastric cancer patients were significantly higher than those from 14 normal individuals with p values <0.0001. Our results suggest the possibility of using the extent of cysteine glutathionylation at β‐93 of hemoglobin as an oxidative stress biomarker candidate for gastric cancer.     

Exfoliation of montmorillonite by the insertion of disklike micelles via the soap‐free emulsion polymerization of methyl methacrylate

Montmorillonites (MMTs) intercalating a potassium persulfate initiator were readily exfoliated in the presence of polymerizing methyl methacrylate during soap‐free emulsion polymerization. Because of the confined space, the polymerizing chains were aggregated into a disk form inside the clay interlayer regions for micellation. It was surprising to find from X‐ray diffraction analysis that the exfoliation of MMT was almost completed in the micellation stage. Further polymerization afforded latex particles of exfoliated poly(methyl methacrylate) (PMMA)–MMT nanocomposites. In addition, two kinds of MMT nanosheets were collected by the removal of PMMA with toluene: One was a single‐layer nanosheet with a thickness of 1.25 nm, and the other was a stacked sheet with an average thickness of 7.5 nm that may have consisted of six individual layers. Electron diffraction analysis revealed that if the individual layer of an MMT nanosheet were not a single crystal, it should contain an ultrathin layer of ice with a commonly occurring hexagonal phase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5572–5579, 2006