Synthesis of SMA by RAFT polymerization and its dispersion of TiO2 in aqueous solution.

Styrene-maleic anhydride copolymer (SMA) with controlled molecular weight (M n) and narrow dispersity was prepared by RAFT polymerization. The effect of reaction time on monomer conversion was investigated, and the conversion of monomer could achieve 99.1% after 24 h at the temperature of 55 °C. The synthesized SMA was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC). The result demonstrated that the polymerization of SMA was well controlled and the dispersity (D) of SMA was lower than 1.20. Furthermore, SMA copolymers with narrow dispersity and well-regulated M n (denoted SMA1500, SMA3000, SMA5000, SMA8000, and SMA15800, respectively) were obtained by adjusting the molar ratio of monomer to the chain transfer agent. Moreover, the synthesized SMA was hydrolyzed in NaOH aqueous solution. Then the dispersion of TiO2 in aqueous solution by the hydrolyzed SMA and SZ40005 (the industrial product) were studied. The agglomerate size, the viscosity and the fluidity of TiO2 slurry were tested. The results show that the performance of dispersity for TiO2 in water by SMA prepared via RAFT was better than that of SZ40005. It was found that the viscosity of the TiO2 slurry dispersed by SMA5000 was the lowest among the SMA copolymers tested, and the viscosity value of the TiO2 slurry with a pigment loading of 75% was only 76.6 cp.

Mechanisms of U87 astrocytoma cell uptake and trafficking of monomeric versus protofibril Alzheimer's disease amyloid-ß proteins.

A significant hallmark of Alzheimer's disease is the formation of senile plaques in the brain due to the unbalanced levels of amyloid-beta (Aß). However, although how Aß is produced from amyloid precursor proteins is well understood, little is known regarding the clearance and metabolism of various Aß aggregates from the brain. Similarly, little is known regarding how astrocytes internalize and degrade Aß, although astrocytes are known to play an important role in plaque maintenance and Aß clearance. The objective of this study is to investigate the cellular mechanisms that mediate the internalization of soluble monomeric versus oligomeric Aß by astrocytes. We used a combination of laser confocal microscopy and genetic and pharmacological experiments to dissect the internalization of sAß42 and oAß42 and their postendocytic transport by U87 human brain astrocytoma cell line. Both Aß42 species were internalized by U87 cells through fluid phase macropinocytosis, which required dynamin 2. Depleting LDL receptor-related protein 1 (LRP1) decreased sAß42 uptake more significantly than that of oAß42. We finally show that both Aß42 species were rapidly transported to lysosomes through an endolytic pathway and subjected to proteolysis after internalization, which had no significant toxic effects to the U87 cells under relatively low concentrations. We propose that macropinocytic sAß42 and oAß42 uptake and their subsequent proteolytic degradation in astroglial cells is a significant mechanism underlying Aß clearance from the extracellular milieu. Understanding the molecular events involved in astrocytic Aß internalization may identify potential therapeutic targets for Alzheimer's disease.