Oligonucleotide Immobilization and Hybridization on Aldehyde-Functionalized Poly(2-hydroxyethyl methacrylate) Brushes.

DNA biosensing requires high oligonucleotide binding capacity interface chemistries that can be tuned to maximize probe presentation as well as hybridization efficiency. This contribution investigates the feasibility of aldehyde-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA) brush-based interfaces for oligonucleotide binding and hybridization. These polymer brushes, which allow covalent immobilization of oligonucleotides, are prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of HEMA followed by a postpolymerization oxidation step to generate side chain aldehyde groups. A series of polymer brushes covering a range of film thicknesses and grafting densities was investigated with regard to their oligonucleotide binding capacity as well as their ability to support oligonucleotide hybridization. Densely grafted brushes were found to have probe oligonucleotide binding capacities of up to ∼30 pmol/cm(2). Increasing the thickness of these densely grafted brush films, however, resulted in a decrease in the oligonucleotide binding capacity. Less densely grafted brushes possess binding capacities of ∼10 pmol/cm(2), which did not significantly depend on film thickness. The oligonucleotide hybridization efficiencies, however, were highest (93%) on those brushes that present the lowest surface concentration of the probe oligonucleotide. These results highlight the importance of optimizing the probe oligonucleotide surface concentration and binding interface chemistry. The versatility and tunability of the PHEMA-based brushes presented herein makes these films a very attractive platform for the immobilization and hybridization of oligonucleotides.

Polymer brush gradients grafted from plasma-polymerized surfaces.

A new method for generating a surface density gradient of polymer chains is presented. A substrate-independent polymer deposition technique was used to coat materials with a chemical gradient based on plasma copolymerization of 1,7-octadiene and allylamine. This provided a uniform chemical gradient to which initiators for atom transfer radical polymerization (ATRP) were immobilized. After surface-initiated atom transfer radical polymerization (SI-ATRP), poly(2-hydroxyethyl methacrylate) (PHEMA) chains were grafted from the surface and the measured thickness profiles provided direct evidence for how surface crowding provides an entropic driving force resulting in chain extension away from the surface. Film thicknesses were found to increase with the position along the gradient surface, reflecting the gradual transition from collapsed to more extended surface-tethered polymer chains as the grafting density increased. The method described is novel in that the approach provides covalent linkages from the polymer coating to the substrate and is not limited to a particular surface chemistry of the starting material.

Polymer-Brush-Templated Three-Dimensional Molybdenum Sulfide Catalyst for Hydrogen Evolution.

Earth-abundant hydrogen evolution catalysts are essential for high-efficiency solar-driven water splitting. Although a significant amount of studies have been dedicated to the development of new catalytic materials, the microscopic assembly of these materials has not been widely investigated. Here, we describe an approach to control the three-dimensional (3D) assembly of amorphous molybdenum sulfide using polymer brushes as a template. To this end, poly(dimethylaminoethyl methacrylate) brushes were grown from highly oriented pyrolytic graphite. These cationic polymer films bind anionic MoS42- through an anion-exchange reaction. In a final oxidation step, the polymer-bound MoS42- is converted into the amorphous MoSx catalyst. The flexibility of the assembly design allowed systematic optimization of the 3D catalyst. The best system exhibited turnover frequencies up to 1.3 and 4.9 s-1 at overpotentials of 200 and 250 mV, respectively. This turnover frequency stands out among various molybdenum sulfide catalysts. The work demonstrates a novel strategy to control the assembly of hydrogen evolution reaction catalysts.

Therapeutic effect of caffeic acid phenethyl ester on cerulein-induced acute pancreatitis.

AIM: To evaluate the therapeutic role of caffeic acid phenethyl ester (CAPE) in a rat model of cerulean-induced acute pancreatitis (AP). METHODS: Seventy male Wistar albino rats were divided into seven groups. Acute edematous pancreatitis was induced by subcutaneous cerulein injection (20 microg/kg) four times at 1-h intervals. CAPE (30 mg/kg) was given by subcutaneous injection at the beginning (CAPE 1 group) and 12 h after the last cerulein injection (CAPE 2 group). Serum amylase, lipase, white blood cell count, and tumor necrosis factor (TNF)-alpha levels were measured, and pancreatic histopathology was assessed. RESULTS: In the AP group, amylase and lipase levels were found to be elevated and the histopathological evaluation showed massive edema and inflammation of the pancreas, with less fatty necrosis when compared with sham and control groups. Amylase and lipase levels and edema formation decreased significantly in the CAPE therapy groups (P < 0001); especially in the CAPE 2 group, edema was improved nearly completely (P = 0001). Inflammation and fatty necrosis were partially recovered by CAPE treatment. The pathological results and amylase level in the placebo groups were similar to those in the AP group. White blood cell count and TNF-alpha concentration was nearly the same in the CAPE and placebo groups. CONCLUSION: CAPE may be useful agent in treatment of AP but more experimental and clinical studies are needed to support our observation of beneficial effects of CAPE before clinical usage of this agent.

The beneficial effect of propolis on cerulein-induced experimental acute pancreatitis in rats.

BACKGROUND/AIMS: Inflammatory cytokines and oxidative stress have a central role in the pathogenesis of acute pancreatitis. Propolis is a resinous hive product collected by honeybees from various plant sources and has anti-inflammatory and anti-oxidant effects. The present work aimed to investigate the therapeutic role of ethanolic extract of propolis on a cerulein-induced acute pancreatitis model in rats. METHODS: Seventy male Wistar albino rats were used in the study. Acute edematous pancreatitis was induced by subcutaneous cerulein injection (20 microg/kg) four times at one-hour intervals. Ethanolic extract of propolis 300 mg/kg was given subcutaneously at the beginning of the procedure (ethanolic extract of propolis-1 group) or 12 h after the last cerulein injection (ethanolic extract of propolis-2 group). Serum amylase and lipase levels, white blood cell count and serum tumor necrosis factor-alpha levels were measured and pancreatic tissue was evaluated histologically. RESULTS: In the acute pancreatitis group, serum amylase and lipase levels were found to be elevated and the histopathological evaluation of the tissue revealed massive edema and inflammation with less fatty necrosis when compared to the sham and control groups. Serum amylase and lipase levels and edema formation were significantly decreased in the ethanolic extract of propolis-treated groups (p<0.001). In the ethanolic extract of propolis-2 group, in particular, tissue edema was improved markedly (p=0.001). Tissue inflammation and fatty necrosis were decreased with ethanolic extract of propolis treatment; however, the improvement was not statistically significant. CONCLUSIONS: Treatment with ethanolic extract of propolis improved the biochemical and histopathological findings in a rat model of experimental pancreatitis. Although our findings suggest that ethanolic extract of propolis might be considered an effective agent for the treatment of acute pancreatitis, this notion should be supported with further experimental and clinical investigations.