The effect of surface wettability on induction and growth of neurites from the PC-12 cell on a polymer surface

Surface properties of polymeric devices that are used to regenerate nervous damage are a point to be considered for axon regeneration in nerve system. In our previous studies, we prepared a wettability gradient on polyethylene (PE) surfaces using a corona discharge treatment from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces were oxidized gradually with increasing power. The effect of surface wettability on the different types of cells has an important role for cell adhesion and proliferation. The purpose of this study is to investigate neurite formation on polymer surfaces with different wettability. Induction and growth of neurites from the rat pheochromocytoma (PC-12) cells attached on the polymer surfaces with different hydrophilicity were investigated using the wettability gradient PE surfaces prepared by a corona discharge treatment. Neurites were investigated for number and length of neurites in terms of surface wettability. It was observed that neurite formation of PC-12 cells was increased more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. From those results, it could be assumed that initial adhesion of PC-12 cells was caused by more calf serum (CS) protein than nerve growth factor (NGF), whereas the neurite formation of PC-12 cells was caused by more NGF than CS protein. It follows from what has been said thus far that PC-12 cells are a differentiated neuronal phenotype with a long neurite at around the position 2.5 cm (water contact angle of about 55 deg). In conclusion, surface wettability plays an important role for neurite formation on the polymer surfaces for axon regeneration.     

Immobilized streptavidin gradients as bioconjugation platforms

Surface density gradients of streptavidin (SAV) were created on solid surfaces and demonstrated functionality as a bioconjugation platform. The surface density of immobilized streptavidin steadily increased in one dimension from 0 to 235 ng cm(-2) over a distance of 10 mm. The density of coupled protein was controlled by its immobilization onto a polymer surface bearing a gradient of aldehyde group density, onto which SAV was covalently linked using spontaneous imine bond formation between surface aldehyde functional groups and primary amine groups on the protein. As a control, human serum albumin was immobilized in the same manner. The gradient density of aldehyde groups was created using a method of simultaneous plasma copolymerization of ethanol and propionaldehyde. Control over the surface density of aldehyde groups was achieved by manipulating the flow rates of these vapors while moving a mask across substrates during plasma discharge. Immobilized SAV was able to bind biotinylated probes, indicating that the protein retained its functionality after being immobilized. This plasma polymerization technique conveniently allows virtually any substrate to be equipped with tunable protein gradients and provides a widely applicable method for bioconjugation to study effects arising from controllable surface densities of proteins.     

Interactions of proteins and cells on functional group gradient surfaces

Charge gradient and comb-like polyethylene oxide (PEO) gradient surfaces were prepared on low density polyethylene (PE) sheets by corona discharge treatment with gradually increasing power and the following graft copolymerization of chargeable functional group- and PEO-containing vinyl monomers, respectively. Those gradient surfaces were used to investigate protein or cell interactions in relation to the surface functional groups and their density of polymeric materials.     

Preparation and characterization of functional group gradient surfaces

Functional group gradient surfaces where the density of functional groups changes gradually along the sample length were prepared. The functional group (? COOH, ? CONH₂, and ? OH group) gradient surfaces were produced by the treatment of low-density PE sheets using a corona with gradually increasing power, followed by the graft copolymerization of acrylic acid and subsequent substitution reaction of carboxylic acid groups to amide or hydroxyl groups. The prepared gradient surfaces were characterized by the measurement of water contact angle, FTIR-ATR, and ESCA. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of the surface functional groups and their density of polymeric materials. © 1994 John Wiley & Sons, Inc.     

Surface graft polymerization of glycidyl methacrylate onto polyethylene and the adhesion with epoxy resin

Surface graft polymerization of glycidyl methacrylate (GMA) was carried out onto a high- density polyethylene (PE) sheet pretreated with corona to introduce peroxides onto the PE surface. Graft polymerization of GMA was effected by UV irradiation of the coronatreated PE in the presence of monomer solution without the use of any photosensitizer. The graft layer was found by staining the PE cross section to localize in the surface region of PE. The physical change in the PE surface was characterized by scanning electron microscopy, while the chemical changes due to the GMA graft polymerization were assessed by the dynamic contact angle, FT-IR, and x-ray photoelectron spectroscopy (XPS) measurement. The peroxide formation by corona exposure was confirmed by the XPS measurement after derivatization with SO₂. The epoxy groups introduced onto the PE surface by the GMA graft polymerization were reactive with water (in the presence of HCI) and amines. The adhesion between the GMA-grafted PE and an epoxy resin was studied by means of a shear strength test method. The GMA-grafted PE exhibited strong interfacial adhesion with the epoxy resin, compared to the original and corona-treated PE. The adhesion strength of the GMA-grafted PE was nearly two times higher than that of the corona-treated PE. This strongly suggests that the enhanced adhesion between the surface-grafted PE and the epoxy resin is ascribed to covalent bonding of the epoxy groups on the GMA-grafted surface to the amines in the epoxy resin. © 1995 John Wiley & Sons, Inc.     

Oxidation of polyethylene surface by corona discharge and the subsequent graft polymerization

Oxidation of a polyethylene (PE) surface by corona discharge and the subsequent graft polymerization of acrylamide (AAm) were studied. The maximum amount of peroxides introduced by corona treatment at a voltage of 15 kV was about 2.3 × 10^?9 mol cm^?2. The decomposition rate of peroxide and the dependence of graft amount on the storage period of the corona-treated PE films showed that there were several kinds of peroxides, the labile one being mainly responsible for the initiation of graft polymerization. When the corona-treated film was brought into contact with a deaerated aqueous solution of AAm, graft polymerization took place more strongly with the treatment time, but was reduced after passing a maximum. Although the x-ray photoelectron spectroscopic analyses of the corona-treated PE films showed homogeneous oxidation of the outer polymer surface by corona discharge, optical microscopy on the cross section of the grafted film revealed the graft polymerization to be limited to a very thin surface region.     

Directed motion of a polyelectrolyte micelle along tethered chains of oppositely charged polyelectrolyte brush

The complexation of different single polyelectrolyte (PE) micelles formed by linear diblock copolymers with oppositely charged brushes with varying grafting densities and charge content was studied by means of molecular dynamics simulations using the primitive model. We found that all micelles perform a directed motion along the vertical z axis on the grafted surface where they trapped while on the other axes the motion is restricted in a circle in which the diameter decreases with the increase of the hydrophilic length of the linear diblock copolymer. The motion of micelles is characterized as super diffusion inside brushes with low densities and low charge content. At high grafting densities and charge content the diffusion becomes Fickian or slightly subdiffusive. The number of the absorbed brush chains on the micelle corona increases almost monotonically with the increase of brush grafting density or with the decrease of charge content. The distance from the surface in which the micelle is trapped can be controlled by the charge density along the grafted PE chain. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 621–631     

Diameter dependence of hybrid shish‐kebab structure in polyethylene/carbon material fiber composites

PE chains can proceed template crystal growth on multi‐walled carbon nanotubes (MWCNTs) surface and develop into hybrid shish‐kebab (HSK) abiding by the “soft epitaxy” mechanism. For large‐diameter carbon nanofiber (CNF), the lattice matching and epitaxy are the main mechanism for hybrid structure formation under the static state. This study provided a new understanding of HSK formation, wherein PE underlay on the surface of carbon material fiber played an important role. The shear flow induced PE chains to orient along the CNF surface and formed PE underlayer. Subsequently, ordered subglobules were periodically formed along the CNF axis and finally evolved to typical HSK structures with well‐aligned arraying PE lamellae rather than random one. As the diameter increased to 7000 nm, even though the graphite (002) planes in carbon fibers (CFs) was similar to that in CNFs, the attractive van der Waals interactions between CFs and PE chains were too weak to drive enough PE chains to absorb on the CFs surface and form PE underlay even under the shear flow, leading to the absence of PE lamellae on the CF surface. Based on that, the “soft epitaxy” could be the main formation mechanism of HSK structures for carbon material fibers regardless of their diameters. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 297–303     

Carbon fiber bundle-Au-Hg dual-electrode detection for capillary electrophoresis

Normal-phase high-performance liquid chromatography was used on a preparative scale to seperate phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylcholine (PC) phospholipids from soybean. Separation was achieved using mixtures of three solvents, hexane, methanol and isopropanol. The optimized mobile phase compositions were experimentally determined while operating in a linear gradient mode using 15, 5-20, 25-40, and 40-63 microm preparative particles as well as 4 microm analytical particles. A gradient mobile phase was established on a commmercially available analytical Nova-Pak column such that hexane linearly decreased from 85 to 0 as isopropanol and methanol linearly increased in two gradient steps from 10 to 30 and 5 to 70 respectively. The total run time was 25 min at a flow-rate of 1.5 ml/min. A slight change in mobile phase composition was required to increase the resolution of phospholipids. The 15 microm particle size gave the best separation of the preparative particle sizes examined based on their resolutions between PE and PI and PI and PC. Finally, the retention factors of PE and PC were correlated in terms of mobile phase composition.     

Surface changes brought about by corona discharge treatment of polyethylene film and the effect on subsequent microbial colonisation

Microbial colonisation of synthetic plastic films is normally slow, which affects the total period of biodegradation. Correlation between the modified surface condition and the ability for microorganisms to colonise low-density polyethylene (LDPE) film was studied. Corona discharge treatment was applied to obtain enriched and activated surface condition of LDPE film. It was found from water contact angle and FTIR spectrum evaluations that surface energy was significantly increased due to production of free radicals. Stabilised oxidised LDPE surface was also obtained by further exposure to the corona which gave more suitable condition for subsequent colonisation. Results were compared with UV irradiated (photo-oxidised) LDPE films. Colonisation of corona discharged and UV treated LDPE films were tested in the laboratory environment using known fungal isolates and in a natural compost environment. More active microbial colonisation was observed in all cases for corona discharged and UV treated LDPE films. Far longer UV exposure was required to have the same physicochemical and biological effect as the corona discharge treatment.     

Purification of Complex of SAV1 with PP1A

SAV1 is a core component involved in the Hippo pathway which can control the organ size via regulating cell proliferation and apoptosis simultaneously. We explored the regulatory mechanism of SAV1. We established the HEK293T cell pool, the cells in which can stably express SAV1 by retroviruses infection and found that SAV1 stable cells reduced the movement of themselves and resulted in multicellular aggregation. We purified SAV1 interacting protein complex using streptavidin resin and subsequently analyzed the digested peptides by high performance liquid chromatography(HPLC)-MS/MS. Results show that about 150 proteins were identified in the complex of SAV1 with protein. TUBA1A, OTUD4, and ATD were identified as proteins interacting with SAV1. Importantly, PP1A, serine/threonine protein phosphatase PP1-alpha 1 catalytic subunit, was also in the top 10 list. The interaction between PP1A and SAV1 was detected by both co-immunoprecipitation(CO-IP) and immunostaining. Our results indicate that PP1A might be the phosphatase of SAV1 and may take part in the regulation of the Hippo pathway.     

First-principles study of superabundant vacancy formation in metal hydrides

Recent experiments have established the generality of superabundant vacancies (SAV) formation in metal hydrides. Aiming to elucidate this intriguing phenomenon and to clarify previous interpretations, we employ density-functional theory to investigate atomic mechanisms of SAV formation in fcc hydrides of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au. We have found that upon H insertion, vacancy formation energies reduce substantially. This is consistent with experimental suggestions. We demonstrate that the entropy effect, which has been proposed to explain SAV formation, is not the main cause. Instead, it is the drastic change of electronic structure induced by the H in the SAV hydrides, which is to a large extent responsible. Interesting trends in systems investigated are also found: ideal hydrides of 5d metals and noble metals are unstable compared to the corresponding pure metals, but the SAV hydrides are more stable than the corresponding ideal hydrides, whereas opposite results exist in the cases of Ni, Rh, and Pd. These trends of stabilities of the SAV hydrides are discussed in detail and a general understanding for SAV formation is provided. Finally, we propose an alternative reaction pathway to generate a SAV hydride from a metal alloy.     

有机-无机复合载体茂锆催化剂的制备及乙烯聚合

合成了组成为聚(4-乙烯基吡啶)-硅胶(SAV)的有机-无机复合载体茂锆催化剂,并用固体13C-NMR谱、元素分析(EA)、光电子能谱(XPS)等方法进行了表征.发现由SAV负载的茂锆催化剂可在相对较低的甲基铝氧烷(Al/Zr=600)用量下聚合乙烯.其活性(1.12×103kg PE/mol Zr.h)远高于SiO2负载的茂锆催化剂(0.22×103kg PE/mol Zr.h).     

Novel AC and DC Non-Thermal Plasma Sources for Cold Surface Treatment of Polymer Films and Fabrics at Atmospheric Pressure

Novel types of non-thermal plasma sources at atmospheric pressure based on multi-pin DC (direct current) diffusive glow discharge and AC (alternative current) streamer barrier corona have been elaborated and tested successfully for cold surface treatment of polymer films [polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET),] and polyester fabric. Results on physical properties ofdischarges mentioned and output energy characteristics of new plasma sources as well as data on after-treatment changes in wettability of films and fabrics are presented. The main goal of this study was to find out the experimental conditions for gas discharge and surface processing to achieve a remarkable wettability change for a short treatment time.     

聚乙烯在羟基化β-石英(100)表面上的有序吸附

利用分子动力学模拟方法研究了聚乙烯链在羟基化β-石英(100)表面上的吸附. 结果表明, 吸附基底上的规则图案起到模板的作用, 无论是真空还是溶液环境, 都会引导聚乙烯链在表面形成二维沿着[110]方向取向的折叠构型. 为了与聚乙烯的吸附相比较, 进一步研究了聚氧化乙烯链在相同表面上的吸附情况. 结果表明, 极性链与非极性链在极性表面上的吸附情况完全不同.     

Influence of the Particle Size of CaCO3 on the Adhesion of Filled EVA Materials

A surface treatment with corona discharge was used to improve the adhesion properties of ethylene vinyl acetate copolymer (EVA) containing small amounts of four CaCO₃ with different particle size. The nature of the surface modifications produced by the corona discharge treatment and the adhesion to a polychloroprene adhesive were assessed. Treatment of CaCO₃ filled EVA with corona discharge produced a decrease in water contact angle value, irrelevant to the different particle size of the calcium carbonates. The corona discharge treatment created C-O and C=O moieties on the EVA surface and also increased the peel strength, more markedly as the CaCO₃ particle size increased. In general, a mixed (adhesion + cohesive in the EVA) failure in the filled EVA material was produced (assessed by IR-ATR spectroscopy and SEM micrographs of the failed surfaces), but the failure was more cohesive in the EVA containing higher particle size CaCO₃. The durability of the joints was also studied.     

A rod-linker-contained R-phycoerythrin complex from the intact phycobilisome of the marine red alga Polysiphonia urceolata

A linker-contained R-phycoerythrin (R-PE) complex was obtained by the Sephadex G-150 column chromatography from the Polysiphonia urceolata phycobilisome (PBS) that was dis-associated at 37 degrees C for 6 h in the dilute phosphate buffer (pH 7.0) with 5% (m/v) sodium dodecyl sulfate (SDS). The R-PE complex showed three absorption peaks at 498, 538 and 567 nm, and a fluorescence emission maximum at 578 nm. Polypeptide analysis of the complex by the 8-25% (m/v) gradient SDS-polyacrylamide gel electrophoresis demonstrated that it contained three red subunits, alpha(PE)(17.6),beta(PE)(19.2) and gamma(PE)(31.0), and a colorless 35.3 kDa rod-linker L(R)(35.3). Polypeptide proportion of the complex demonstrated that it was a hexamer in aggregate form gamma(PE)(31.6), (alpha(PE)(17.6),beta(PE)(19.2))(3)L(R)(35.3)(alpha(PE)(17.6),beta(PE)(19.2)(3)gamma(PE)(31.6) which is proposed to originate from a rod assembly of hexamer-linker-hexamer the substructure alpha(PE)(17.6),beta(PE)(19.2)(3) of which was decomposed off from the ends of the assembly during the PBS dissociation. The distinctive stability of the prepared hexamer is attributed to a large extent to the electrostatic interaction among its polypeptides, but not to the hydrophobic interaction.     

Profile control in surface amine gradients prepared by controlled-rate infusion

Surface amine gradients that exhibit a wide variety of profiles, including those that incorporate spatially distinct regions having steep and gradual variations in chemical functionality, have been prepared by the sol-gel process using a controlled-rate infusion method. In this work, a substrate that incorporates dimethyl and Si-OH groups is temporally modified with an aminoalkoxysilane (NH(2)(CH(2))(3)Si(OC(2)H(5))(3)) to build a gradient film for which the amine content changes over a 10-20 mm distance. Both X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirm the presence of a chemical gradient across the surface of the film. As expected, a greater density of amine functionalities and lower contact angle were found at the bottom of the gradient relative to the top. The local steepness of the gradient was systematically controlled by changing the rate of infusion. Fast rates of infusion created gradient surfaces where the amine content changed slowly along the surface and never reached saturation, whereas slow rates of infusion formed a surface exhibiting a steep rise in amine content followed by saturation. The steepness of the gradient was also changed at predefined positions along its length by programming the rate of infusion. Gradients prepared using six-step, three-step, and two-step programmed infusion rates are shown. The data fit nicely to a kinetic model that assumes first-order kinetics. The ability to manipulate the gradient profile is particularly vital for applications that rely on mass transport and/or those that require spatial control of gradient properties.     

The effect of organic ligand modification on protein corona formation of nanoscale metal organic frameworks

Nanoscale metal organic frameworks (NMOFs) have been widely reported in biomedical field for their unique porous structure and tunable multifunctionality. However, when administrated in vivo, the protein corona will be formed on the surface of NMOFs, significantly affecting their biodistribution, pharmacokinetics and drug release. Few studies paid attention to the protein corona formation process and its influencing factors of NMOFs. As a well-established strategy for altering structure features of NMOFs, the organic ligand modification may have effect on the protein corona formation process, which is to be investigated. In this study, the zirconium (Zr)-based UIO66 was chosen as model NMOFs, the organic ligand of which was modified with amino group (-NH₂) or carboxyl group (-COOH) to synthesize UIO66-NH₂ and UIO66-2COOH, respectively. Bovine serum albumin (BSA) was chosen as model protein to investigate the protein corona formation process of NMOFs. The current results showed that the -COOH modification remarkably enhanced the BSA adsorption on NMOFs while -NH₂ slightly decreased the protein binding affinity. These differences may be ascribed to the two different dominate protein corona formation modes, i.e., surface coating mode and porous embedded mode. The protein corona formation did not affect the crystal phase of NMOFs but increased the content of α-helix of BSA. Ultimately, upon protein corona formation, the cellular uptake of NMOFs was significantly affected. We believe our study will provide a new research paradigm to the design and applications of NMOFs.     

PVCH-PE-PVCH中PE片晶链轴在柱状微区中的取向

以柱状微相分离结构的聚乙烯基环己烷-聚乙烯-聚乙烯基环己烷(PVCH-PE-PVCH)三嵌段共聚物为研究对象,分别采用压延法和旋转涂膜法制得取向样品。利用偏振红外光谱法测定了PE柱状微区内结晶区中—CH2—基团的面内扭摆振动吸收峰的变化,以此来考察PE晶区折叠链片晶的链轴在柱状微相分离结构中的取向性。结果表明:在压延取向的样品中,由于外力的作用使得PE柱状微区沿着样品流动的方向取向,PE片晶的链轴也同样倾向于沿着平行于PE柱状微区的柱轴方向排列。退火使得PE片晶沿着链轴取向方向的取向程度升高。在由旋转涂膜制得的取向薄膜样品中,PE柱状微区垂直于基板排列,而PE片晶链轴则更倾向于沿着垂直于PE柱状微区的柱轴方向取向。