Synthesis of Poly(N-vinylpyrrolidone) Nanofibers Containing Gold Nanoparticles via Electrospinning Technique

Poly（N-vinylpyrrolidone）（PVP）nanofibers containing gold nanoparticles were prepared by electrospinning method.This simple route was used to prepare composites on a large scale,and the syntheses are simple.The optical property of gold nanoparticles in PVP aqueous solution was investigated by UV-Visible absorption spectra.The morphology of the fibers and the distribution of particles were characterized by transmission electron microscopy.The structure of the composite was characterized by Fourier transform infrared spectroscopy.

Kinetics of Copolymerization of Acrylonitrile with N-Vinylpyrrolidone in H_2O/Dimethyl Sulphoxide Mixture

Kinetics of copolymerization of acrylonitrile(AN) with N-vinylpyrrolidone(NVP) initiated by azodi-isobutyronitrile(AIBN) was investigated in H2O/dimethyl sulphoxide(DMSO) mixture between 50℃ and 70℃ under N2 atmosphere. The rate of copolymerization and particle size were measured respectively. The kinetic equation of copolymerization system is obtained as Rpat 60℃. The overall activation energy for copolymerization system was computed as 87.3kJ.mol-1. Effect of additives of hydroquinone and dioxane on copolymerization was discussed. The polymerization is retarded by hydroquinone and accelerated by dioxane, which confirms the free radical copolymerization of AN with NVP.

Measurement and correlation of solid–liquid phase equilibria for binary and ternary systems consisting of N-vinylpyrrolidone, 2-pyrrolidone and water

The solid–liquid equilibria(SLE)for binary and ternary systems consisting of N-Vinylpyrrolidone(NVP),2-Pyrrolidone(2-P)and water are measured.The phase diagrams of NVP(1)+2-P(2),NVP(1)+water(2),NVP(1)+2-P(2)+1 wt%water(3)and NVP(1)+2-P(2)+2 wt%water(3)are identified as simple eutectic type with the eutectic points at 263.75 K(x_(1E)=0.5427),251.65 K(x_(1E)=0.3722),260.25 K(x_(1E)=0.5031)and256.55 K(x_(1E)=0.4684),respectively.The phase diagram of 2-P(1)+water(2)has two eutectic points(x_(1E)=0.1236,T_E=259.15 K and x_(1E)=0.7831,T_E=286.15 K)and one congruent melting point(x_(1C)=0.4997,T_C=303.55 K)because of the generation of a congruently melting addition compound:2-P·H_2O.The ideal solubility and the UNIFAC models were applied to predict the SLE,while the Wilson and NRTL models were employed in correlating the experimental data.The best correlation of the SLE data has been obtained by the Wilson model for the binary system of NVP+2-P.The UNIFAC model gives more satisfactory predictions than the ideal solubility model.

POLY(N-VINYLPYRROLIDONE)-MODIFIED SURFACES REPEL PLASMA PROTEIN ADSORPTION

The present work aimed to study the interaction between plasma proteins and PVP-modified surfaces under more complex protein conditions. In the competitive adsorption of fibrinogen （Fg） and human serum albumin （HSA）, the modified surfaces showed preferential adsorption of HSA. In 100% plasma, the amount of Fg adsorbed onto PVP-modified surfaces was as low as 10 ng/cm2, suggesting the excellent protein resistance properties of the modified surfaces. In addition, immunoblots of proteins eluted from the modified surfaces after plasma contact confirmed that PVP-modified surfaces can repel most plasma proteins, especially proteins that lalav important roles in the nrocess of blood coagulation.

Interaction of TbCl_3 and lanthanide complexes with poly(N-vinylpyrrolidone)

The interaction of TbC13 and lanthanide（Ⅲ） β-diketonate complexes with poly（N-vinylpyrrolidone） （PVP） polymer was studied using fluorescence spectroscopy. In the presence of PVP the emission of Tb3＋ in cthanolic solution of TbCl3 significantly in- creased owing to the excitation energy transfer from PVP to Tb3＋ ions, which was more efficient as compared to a direct excitation of the Tb3＋ 4f75d1 levels. In contrast, emission of NEt4Tb（hfa）4 and NEt4Eu（hfa）4 complexes was almost completely quenched in solu- tion containing PVP. The PVP bound both Ln3＋ ions and hfa ligands which caused decomposition of Ln-hfa complexes and switched off the excitation energy transfer from the ligand to the emitting Ln3＋ ion. The important role of hydrogen bonds in stabilization of in- teraction ofhfa ligands with PVP was indicated.

NOVEL AMPHIPHILIC FLUORESCENT GRAFT COPOLYMER: SYNTHESIS, CHARACTERIZATION AND ENCAPSULATION OF A HYDROPHOBIC AGENT

Novel amphiphilic fluorescent graft copolymer （PVP-PyAHy） was successfully synthesized by the free radical copolymerization of hydrophobic monomer N-（1-pyrenebutyryl）-N＇-acryloyl hydrazide （PyAHy） with hydrophilic precursor polymers of vinyl-functionalized poly（N-vinylpyrrolidone） （PVP） in DMF. The copolymer is amphiphilic and has intrinsic fluorescence. FT-IR, ^1H-NMR, TEM, gel permeation chromatography-multi-angle laser light scattering, UV-Vis spectroscopy and fluorescence spectroscopy were used to characterize this copolymer. The TEM observation shows that the copolymer PVP-PyAHy forms micelles in aqueous solution. Results of fluorometric measurements illustrate that the critical micelle concentration （CMC） value of PVP-PyAHy in aqueous solution is about 0.90 mg/mL. To examine the encapsulation ability of the copolymer in aqueous media, methyl yellow was employed as a model hydrophobic agent. The loading level of the polymer to methyl yellow is 8.8 mg/g. The cytotoxicity assays for Madin Darby Canine Kidney （MDCK） cells shows good biocompatibility of PVP-PyAHy in vitro. These results suggest the potential of this copolymer PVP-PyAHy as drugs delivery carrier and fluorescent tracer.

Poly(ethylene glycol) and poly(N-vinlypyrrolidone) for improved porcine islet cryopreservation

Water-soluble polymers poly(ethylene glycol) (PEG) and poly(N-vinylpyrrolidone) (PVP) were used to study cryopreservation of porcine islets. DMSO was used as control. The effects of polymer purity, molecular weight (MW) and concentration on islet viability were investigated. The results show that both PVP and PEG are good cyroprotectant candidates for islet cryopreservation. The effects of polymer purity and concentration were significant. Increasing concentration significantly increased the islet viability. However, after the concentration reached a certain level, there was no significant difference in viability probably due to increased viscosity of the polymer solution. The effect of polymer MW was not significant. It is concluded that polymers can be a suitable cryoprotectant for porcine islet cryopreservation. The islet viability is polymer concentration-dependent. It seems that PVP is a better cryoprotectant candidate as compared to PEG because the former showed a fast dissolution rate in culture medium and lower viscosity. The polymer concentration at 30% appears to be the optimal for cryopreservation from the viewpoint of islet viability and medium viscosity.

PROTEIN ADSORPTION AND CELL ADHESION ON RGD-FUNCTIONALIZED SILICON SUBSTRATE SURFACES

A method was developed to modify silicon surfaces with good protein resistance and specific cell attachment. A silicon surface was initially deposited using a block copolymer of N-vinylpyrrolidone （NVP） and 2-hydroxyethyl methacrylate （HEMA） （PVP-b-PHEMA） film through surface-initiated atom transfer radical polymerization and then further immobilized using a short arginine-glycine-aspartate （RGD） peptide. Our results demonstrate that the RGD-modified surfaces （Si-RGD） can suppress non-specific adsorption of proteins and induce the adhesion of L929 cells. The Si-RGD surface exhibited higher cell proliferation rates than the unmodified silicon surface. This research established a simple method for the fabrication of dual-functional silicon surface that combines antifouling and cell attachment promotion.