A photoresponsive molecularly imprinted polymer with rapid visible-light-induced photoswitching for 4-ethylphenol in red wine.

The trans to cis isomerization of the azobenzene chromophore in most azobenzene-based photoresponsive molecularly imprinted polymers (MIPs) is initiated by UV irradiation. This limits the application of these materials in cases where UV light toxicity is an issue, such as in biological systems, food monitoring, and drug delivery. Herein we report a tetra-ortho-methyl substituted azobenzene, (4-[(4-methacryloyloxy)-2,6-dimethyl phenylazo]-3,5-dimethyl benzenesulfonic acid (MADPADSA). The photoswitching of MADPADSA could be induced by visible-light irradiation (550 nm for trans to cis and 475 nm for cis to trans) in 4-hydroxyethylpiperazineethanesulfonic acid (HEPES) buffer-ethanol (4:1, v/v) at pH 7.0, however, the photoisomerization was slow. With the use of MADPADSA as a functional monomer, NaYF4:Yb3+,Er3+ as a substrate, 4-ethylphenol (4-EP) as a template, a novel photoresponsive surface molecularly imprinted polymer NaYF4:Yb3+,Er3+@MIP was obtained. The NaYF4:Yb3+,Er3+@MIP displayed rapid visible-light-induced photoswitching. The NaYF4:Yb3+,Er3+ substrate could efficiently increase the trans to cis isomerization rate of the photoresponsive MIP on its surface, which was faster than that of the corresponding azobenzene monomer MADPADSA. Possible reasons for this effect were investigated by fluorescence spectroscopy. NaYF4:Yb3+,Er3+@MIP displayed good specificity toward 4-EP with a specific binding constant (Kd) of 3.67 × 10-6 mol L-1 and an apparent maximum adsorption capacity (Qmax) of 10.73 µmol g-1, respectively. NaYF4:Yb3+,Er3+@MIP was applied to determine the concentration of 4-EP in red wine with good efficiency and a limit of detection lower than the value that could cause an unpleasant off-flavor.

A photoresponsive surface molecularly imprinted polymer shell for determination of trace griseofulvin in milk.

A new photoresponsive surface molecularly imprinted polymer shell (PMIPS) was developed for determination of trace griseofulvin from milk. The PMIPS was prepared by surface imprinting technique using poly(styrene-co-methacrylic acid) (PS-co-PMMA) microspheres as the sacrificial substrate, griseofulvin as the template, a photoresponsive azobenzene derivative 4-((4-(methacryloyloxy)phenyl)diazenyl)-3,5-dimethyl benzenesulfonic acid as the functional monomer, and triethanolamine trimethacrylate as the cross-linker. The PMIPS was obtained after the removal of the sacrificial PS-co-PMMA core from the surface imprinted core-shell microspheres, PS-co-PMAA@PMIP. Compared with PS-co-PMAA@PMIP, PMIPS displayed better properties such as higher surface area and pore volume, rapid photo-isomerization rate, and higher adsorption capacities, specific binding constant and binding density. The PMIPS could efficiently detect griseofulvin in complex samples such as milk.

Photoresponsive hollow molecularly imprinted polymer for trace triamterene in biological samples.

This paper reports a photoresponsive hollow molecularly imprinted polymer for the determination of trace triamterene in biological sample. The photoresponsive hollow molecularly imprinted polymer was prepared on sacrificial silica microspheres via surface imprinting technique through atom transfer radical polymerization using a novel water-soluble azobenzene derivative, 4-[(4-methacryloyloxy)phenylazo]-3,5-dimethyl benzenesulfonic acid, as the functional monomer, and the sacrificial silica core was subsequently removed using HF etching method with 1.25vol.% HF ethanolic solution. The morphologies and properties of the photoresponsive hollow molecularly imprinted polymer were further characterized and compared systematically with the corresponding photoresponsive surface molecularly imprinted polymer. Compared with surface imprinted polymer, the hollow material displayed higher binding capacity, better recognition ability, faster mass-transfer rate, and larger isomerization rate constants toward triamterene. The static binding properties of the imprinted materials were investigated under three irradiation conditions. The photoresponsive hollow molecularly imprinted polymer showed better specificity toward triamterene than its structural analogues (folic acid and caffeine) as examined by UV-vis and HPLC. The photoresponsive hollow molecularly imprinted polymer was utilized for the determination of trace triamterene in biological samples (human urine and serum) with advantages of simple sample pre-treatment, good recovery and good sensitivity.

Photoresponsive hollow molecularly imprinted polymer for the determination of trace bisphenol A in water.

A photoresponsive hollow molecularly imprinted polymer (PHMIP) was fabricated for photoresponsive recognition and determination of trace bisphenol A (BPA) in aqueous media using a water-soluble azo compound as the functional monomer. The PHMIP was prepared on sacrificial silica microspheres by surface imprinting and subsequent removal of the silica core. The PHMIP displayed photocontrolled recognition for BPA. SEM, TEM, FT-IR, TGA and N2 adsorption-desorption analyses confirmed successful formation of the hollow structure. The PHMIP displayed higher binding capacity, a larger specific area, and faster mass transfer rate than its corresponding surface molecularly imprinted polymer. The PHMIP was used to determine trace BPA in real samples with a limit of detection of 0.5ppm. For samples spiked at 0-10ppm, the BPA recoveries were in the range of 93.0%-99.0%. This PHMIP-based method provides convenient and inexpensive detection method for trace BPA in environmental samples. This method is especially suitable for determining materials that do not possess specific spectroscopic or luminescent properties.

Altered diurnal variation and localization of clock proteins in the remnant kidney of 5/6 nephrectomy rats.

AIM: To investigate the localization and diurnal variation of clock proteins (BMAL1, PER2) and clock output protein (DBP) in the remnant kidney of 5/6 nephrectomy rats (STNx). METHODS: Male wistar rats were randomly divided into sham STNx group (Control) and STNx group. Rats were synchronized 12 weeks to the light: dark cycle 12:12 with light on from 07.00 hours (Zeitgeber time ZT 0). Kidneys were collected to detect the localization and expression rhythm of clock proteins (BMAL1, PER2 and DBP) every 4 h throughout the day by immunohistochemistry and Western blotting. RESULTS: Clock proteins showed diurnal rhythm in the kidney of the control. But diurnal rhythm of clock proteins changed in the STNx rats. Acrophase of BMAL1, DBP and PER2 advanced 4 h, respectively; mesor of clock proteins increased in the STNx rats. BMAL1 was located in endothelial cells of glomerulus and tubular interstitial vasculars, and it was also expressed in nucleus of tubular cells in cortex and medulla. PER2 was mainly expressed in proximal tubular cells at the juncture of cortex and medulla. DBP was widely expressed in the kidney. The localization of BMAL1 and PER2 were changed in remnant kidneys of the STNx group. CONCLUSION: The localization and diurnal variation of BMAL1, DBP and PER2 are changed in remnant kidney of 5/6 nephrectomy rats and are involved in diurnal rhythm of renal function.

Impaired activation of phosphatidylinositol 3-kinase by leptin is a novel mechanism of hepatic leptin resistance in NAFLD.

BACKGROUND/AIMS: The aim of this study was to detect the levels of leptin in serum and the expression of leptin, obesity receptor (OB-R), phosphatidylinositol 3-Kinase (p85) (PI3-K p85) and phospho-Akt-kinase (Akt) in non-alcoholic fatty liver disease (NAFLD). METHODOLOGY: The expressions of leptin, OB-R and PI3-K/ Akt kinase pathway were examined by immunohistochemistry. The level of leptin in serum was measured by radioimmunoassay. RESULTS: In agreement with significantly elevated serum leptin levels in NAFLD patients (p<0.05), expression of leptin, OB-R and PI3-K (p85) was significant higher in NAFLD patients (p<0.05) compared with the control patients. In contrast, expression of Akt was significantly down-regulated in the NAFLD patients (p<0.05). Moreover, PI3-K (p85) expression was significantly, positively correlated with leptin (r= 0.365, p<0.05) but negatively correlated with Akt (r=-0.854, p<0.01). CONCLUSIONS: Leptin may be involved in NAFLD pathogenesis by activating the PI3-K/Akt kinase pathway via OB-R and the defective leptin activation of PI3-K is a novel mechanism of leptin resistance in NAFLD.

Diallyl disulfide-induced G2/M arrest of human gastric cancer MGC803 cells involves activation of p38 MAP kinase pathways.

AIM: To determine the role of p38 MAP kinase signal transduction pathways in diallyl disulfide (DADS)-induced G2/M arrest in human gastric cancer MGC803 cells. METHODS: MGC803 cell growth inhibition was measured by MTT assay. Phase distribution of cell cycle was analyzed by flow cytometry. Expression of Cdc25C, p38, phosphorylation of p38 (pp38) were determined by Western blotting. RESULTS: MTT assay showed that SB203580, a specific p38 MAPK inhibitor blocked DADS-induced growth inhibition. Flow cytometry analysis revealed that treatment of MGC803 cells with 30 mg/L DADS increased the percentage of cells in the G2/M phase from 9.3% to 39.4% (P<0.05), whereas inhibition of p38 activity by SB203580 abolished induction of G2/M arrest by DADS. Western blotting showed that phosphorylation of p38 was increased 3.52-fold following treatment of MGC803 cells with 30 mg/L DADS for 20 min (P<0.05), whereas Cdc25C was decreased 68% following treatment of MGC803 cells with 30 mg/L DADS for 24 h (P<0.05). Decreased Cdc25C protein expression by DADS was attenuated by SB203580 (P<0.05). CONCLUSION: DADS-induced G2/M arrest of MGC803 cells involves activation of p38 MAP kinase pathways. Decreased Cdc25C protein expression by p38 MAPK played a crucial role in G2/M arrest after treatment with DADS.