Anisotropic oxygen plasma etching of colloidal particles in electrospun fibers

Oxygen plasma etching of electrospun polymer fibers containing spherical colloids is presented as a new approach towards anisotropic colloidal nanoparticles. The detailed morphology of the resulting nanoparticles can be precisely controlled in a continuous way. The same approach is also amenable to prepare inorganic nanoparticles with double-sided patches.     

The study of a single BGC823 cell using Fourier transform infrared microspectroscopic imaging

In order to investigate gastric cancer at cellular and sub-cellular level, a single human gastric adenocarcinoma BGC823 cell was studied by an infrared microscope equipped with a focal plane array (FPA) detector. The spectra showed difference between the nucleus and the endoplasmic reticulum (ER) of the BGC823 cell. The peak of vasPO2- was shifted to a higher wavenumber at the nucleus compared with that at the ER. The height ratios of 2954 cm(-1)/2922 cm(-1) (CH3/CH2) and 1088 cm(-1)/1539 cm(-1) (DNA/amide II) of the nucleus were significantly higher than those of the ER. Furthermore, chemical images reveal the intensity distributions of lipids, proteins and DNA of the single BGC823 cell, and the intense absorptions of proteins and DNA were observed in the nuclear region of the cell while the intense absorption of lipids was found in the ER region of the cell. The Fourier transform infrared (FTIR) microspectroscopic imaging result indicates the study of the single gastric cancer cell at sub-cellular level can be beneficial for knowing gastric cancer more which will be of great importance for the study and diagnosis of gastric cancer. The result also suggests that FPA is a useful tool in the study of a single cell and may be a powerful tool for study and diagnosis of gastric cancer.     

Effect of pH on the interaction of vitamin B12 with bovine serum albumin by spectroscopic approaches

The interaction mechanism between vitamin B12 (B12, cyanocobalamin) and bovine serum albumin (BSA) has been investigated by fluorescence, synchronous fluorescence, ultraviolet-vis (UV) absorbance, and three-dimensional fluorescence. The intrinsic fluorescence of BSA was strongly quenched by the addition of B12 in different pH buffer solutions (pH 2.5, 3.5, 5.0, 7.4, and 9.0) and spectroscopic observations are mainly rationalized in terms of a static quenching process at lower concentration of B12 (C(B12)/C(BSA)<5) and a combined quenching process at higher concentration of B12 (C(B12)/C(BSA)>5). The structural characteristics of B12 and BSA were probed, and their binding affinities were determined under different pH conditions. The results indicated that the binding abilities of B12 to BSA in the acidic and basic pH regions (pH 2.5, 3.5, 5.0, and 9.0) were lower than that at simulating physiological condition (pH 7.4). In addition, the efficiency of energy transfer from tryptophan fluorescence to B12 was found to depend on the binding distance r between the donor and acceptor calculated using F?rster's theory. The effect of B12 on the conformation of BSA was analyzed using UV, synchronous fluorescence and three-dimensional fluorescence under different pH conditions. These results showed that the binding of B12 to BSA causes apparent change in the secondary and tertiary structures of BSA.     

Determination of DNA based on localized surface plasmon resonance light scattering using unmodified gold bipyramids

The DNA was determined based on resonance light scattering (RLS) spectrometry and the localized surface plasmon resonance. The gold bipyramids were used as the probes and synthesized by a seed-mediated method. Cetyltrimethylammonium bromide was used as stabilizing agent. DNA can be bound to the gold bipyramids due to electrostatic interaction and aggregates, which results in a strong enhancement of the RLS intensity. Under the optimal conditions, the intensity of RLS is directly proportional to the concentration of DNA in the range from 0.1 to 2.0 μg mL(-1).     

Determination of the sodium 2-mercaptoethanesulfonate based on surface-enhanced Raman scattering

Based on the surface-enhanced Raman scattering (SERS) sodium 2-mercaptoethanesulfonate (mesna) was determined using unmodified gold colloid as the probe. The Raman scattering intensity was obviously enhanced in the presence of sodium chloride. The influence of experimental parameters, such as incubation time, sodium chloride concentration and pH value on SERS performance was examined. Under the optimum conditions, the SERS intensity is proportional to the concentration of mesna in the range of 9.0×10(-8) to 9.0×10(-7) mol/L and detection limit (S/N=3) is 1.16×10(-8) mol/L. The corresponding correlation coefficient of the linear equation is 0.996, which indicates that there is a good linear relationship between SERS intensity and mesna concentration. The experimental results indicate that the proposed method is a viable method for determination of mesna. The real samples were analyzed and the results obtained were satisfactory.     

Chamaejasmine inactivates Akt to trigger apoptosis in human HEp-2 larynx carcinoma cells

In the present study, we investigated the mechanisms of chamaejasmine action on human HEp-2 larynx carcinoma cells, which possess constitutively active Akt. Results indicated that chamaejasmine showed more notable anticancer activity than apigenin against HEp-2, PC-3, NCI-H1975, HT-29 and SKOV-3. Moreover, chamaejasmine presented most significantly inhibition towards HEp-2, with IC?? values of 1.92 μM. Treatment of HEp-2 cells with chamaejasmine (1-4 μM) resulted in signi?cant dose-dependent decrease in Akt phosphorylation at Serine473. Chamaejasmine-mediated dephosphorylation of Akt resulted in inhibition of its kinase activity, which was con?rmed by reduced phosphorylation of proapoptotic proteins BAD and glycogen synthase kinase-3, essential downstream targets of Akt. Inactivation of Akt seems to be associated with downregulation of insulin-like growth factor receptor 1 protein level and inhibition of its autophosphorylation upon chamaejasmine treatment. Exposure to chamaejasmine signi?cantly induced caspase-9 and caspase-3 activity. In vivo, chamaejasmine intake through gavage resulted in inactivation of Akt and induction of apoptosis in HEp-2 tumors. These results suggest that Akt inactivation and dephosphorylation of BAD is a critical event, at least in part, in chamaejasmine-induced HEp-2 cells apoptosis.     

Significant enhancement of the photoelectrochemical activity of TiO2 nanotubes

In the present work, we report on a facile and effective approach to significantly enhance the photocatalytic activity of TiO₂ nanotubes. The TiO₂ nanotubes prepared by the electrochemical oxidation of titanium in dimethyl sulfoxide (DMSO) with 2% HF were treated in a methanol solution under UV light irradiation. In comparison with the untreated TiO₂ nanotubes, the treatment resulted in a dramatic increase in the donor density of the TiO₂ nanotubes by approximately 3 orders of magnitude. The treated TiO₂ nanotubes exhibited a 15-fold enhancement in photocurrent and a 6.8-fold increase in the photoelectrochemical degradation of 4-nitrophenol, significant for hydrogen generation and wastewater treatment.     

Synthetic dye--inorganic salt hybrid colorants for application in thermoplastics

Common synthetic dyes, e.g., Weak Acid Pink Red B (APRB, C.I. 18073), Mordant Blue 9 (MB, C.I.14855) and Acid Brilliant Blue 6B (ABB6B, C.I. 42660), can be removed from water by in situ hybridization with CaCO(3), BaSO(4) and Ca(3)(PO(4))(2) and the resulting hybrids thus prepared used as plastic colorants. All the hybrids can be processed into polypropylene (PP) at 200 °C with good color intensity, color brightness and homogeneous dispersion. The BaSO(4)-MB hybrid exhibits better migration resistance to acid and alkali, and stronger covering power than the BaSO(4)-MB mixture. The thermal stability and UV resistance of the Ca(3)(PO(4))(2)-ABB6B hybrid are better than those of the Ca(3)(PO(4))(2)-ABB6B mixture. The crystallinity of PP is enhanced by incorporation of these hybrids and the use of these hybrids as colorants in PP instead of the dyes alone is determined to be feasible.     

A density functional theory approach to mushroom-like platinum clusters on palladium-shell over Au core nanoparticles for high electrocatalytic activity

Recently, it was found that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation of formic acid (P. P. Fang, S. Duan, et al., Chem. Sci., 2011, 2, 531-539). In an attempt to offer an explanation, we used here carbon monoxide (CO) as probed molecules, and applied density functional theory (DFT) to simulate the surface Raman spectra of CO at this core-shell-cluster NPs with a two monolayer thickness of Pd shell and various Pt cluster coverage. Our DFT results show that the calculated Pt coverage dependent spectra fit the experimental ones well only if the Pt clusters adopt a mushroom-like structure, while currently the island-like structure is the widely accepted model, which follows the Volmer-Weber growth mode. This result infers that there should be a new growth mode, i.e., the mushroom growth mode as proposed in the present work, for Au@Pd@Pt NPs. We suggest that such a mushroom-like structure may offer novel active sites, which accounts for the observed high electrocatalytic activity of Au@Pd@Pt NPs.     

Ionic liquid induced spontaneous symmetry breaking: emergence of predominant handedness during the self-assembly of tetrakis(4-sulfonatophenyl)porphyrin (TPPS) with achiral ionic liquid

The self-assembly and supramolecular chirality of a dianionic tetrakis(4-sulfonatophenyl) porphyrin (TPPS) in the presence of ionic liquids, 1-alkyl-3-methylimidazolium tetrafluoroborate (alkyl = C(2), C(4) or C(6), abbreviated as C(2)mimBF(4), C(4)mimBF(4) and C(6)mimBF(4), respectively), have been investigated. It has been confirmed that mimBF(4) ionic liquids significantly promoted the J-aggregation of TPPS and the alkyl chain length in the imidazolium cation was closely related to the TPPS aggregation, the inducing ability of which decreased in the order of C(2), C(4) or C(6) in side chain. Interestingly, the formed TPPS assemblies with the ionic liquids showed supramolecular chirality although both TPPS and ionic liquids are achiral. It was found that the supramolecular chirality of the TPPS/IL system always appeared after the formation of the J aggregate. The dynamic process of the emergence of the handedness in the initial achiral system was monitored by the time-dependent CD spectra. A mechanism for the transformation of the conventional J-aggregate to the chiral J-aggregate was proposed. The work will lead to a deeper understanding of the chiral symmetry breaking in the supramolecular system.