Polyglutamic Acid Based Polyanionic Shielding System for Polycationic Gene Carriers

For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of p H-sensitive poly（ethylene glycol）-poly（γ-benzyl-L-glutamate-co-glutamic acid）（PEG-PGA（65）, 65 denotes the molar ratio of glutamic acid in poly（γ-benzyl-L-glutamate-co-glutamic acid））. PEG-PGA（65） showed low cytotoxicity and could shield the positive charge of DNA/PEI（1：1） polyplexes efficiently. The transfection was enhanced due to the partially charge shielding in He La cell line at pH of 7.4. There was almost no transfection efficiency when the surface charge of the ternary particles turned to negative at p H of 7.4. However, the transfection efficiency recovered a lot by culturing at p H of 6.0 at the beginning of transfection. Confocal microscopic observation and flow cytometry results showed DNA/PEI polyplexes should be efficiently released and endocytosized at p H 6.0, because of the p H triggered deshielding action of PEG-PGA（65）. Due to the good biocompatibility and suitable p H triggered shielding/deshielding property, PEG-PGA（65） could be a potential shielding system for polycationic gene carriers used in vivo.

Corrosion resistance behavior of gradient microstructure induced by punching deformation and recovery treatment on cupronickel alloy surface

In this study, the gradient grain induced by punching deformation and recovery treatment on a cupronickel alloy surface sample were investigated, and their effects on corrosion resistance were measured by atom force microscopy(AFM), X-ray diffraction(XRD),electrochemical measurement, electron work function(EWF), and contact electrical resistance(CER). The cupronickel alloy surface experienced punching deformation for 60 min and recovery at 300 ℃ for 1 h to produce gradient surface. The grain size measured by XRD is bigger than that measured by AFM, due to X-ray intensity of95 % produced at the depth of 12-20 μm for the crystal planes of(111),(200), and(220). The gradient grain surface, compared to the original surface, shows a 13.7-fold decrease in passivation current density(i), and corrosion potential(Ec) increases by approximately 9.8 %. These results are attributable to the increase in EWF and formation of passivation film with better adhesion and compactness after treatment.