Development of water‐based polymeric dye and its application as a colorant for waterborne polyurethane

In this project, an eco‐friendly aqueous synthesis method of water‐based polymeric dye (WPD) was developed and its potential as a colorant for waterborne polyurethane (WPU) was tested. The WPD was produced by reacting polyethylenimine with commercial reactive dye in the warm alkaline solution. The colored polyurethane membrane was then produced via solution blending of WPD and WPU, followed by air‐drying. The results showed that WPD with a wide variety of colors can be easily synthesized by selecting different precursory reactive dyes and can be easily blended with WPU via moderate stirring. The colored PU membranes have good transparency and the logo under them can be clearly observed. Compared with the pure polyurethane membrane, the absorbance of colored polyurethane membrane at the wavelength of maximum absorption increases at least 20.2% even if the content of WPD within the colored polyurethane membrane is as low as 0.16%, implying that our WPD has excellent color strength. Finally, the colored polyurethane membranes have very high colorfastness to water and can be stored in deionized water for 2 weeks without dissolution of WPD. As a result, our developed WPD is a promising and cost‐effective colorant for WPU. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44710.     

Antheraea pernyi Silk Fibroin-Coated PEI/DNA Complexes for Targeted Gene Delivery in HEK 293 and HCT 116 Cells

Polyethylenimine (PEI) has attracted much attention as a DNA condenser, but its toxicity and non-specific targeting limit its potential. To overcome these limitations, Antheraea pernyi silk fibroin (ASF), a natural protein rich in arginyl-glycyl-aspartic acid (RGD) peptides that contains negative surface charges in a neutral aqueous solution, was used to coat PEI/DNA complexes to form ASF/PEI/DNA ternary complexes. Coating these complexes with ASF caused fewer surface charges and greater size compared with the PEI/DNA complexes alone. In vitro transfection studies revealed that incorporation of ASF led to greater transfection efficiencies in both HEK (human embryonic kidney) 293 and HCT (human colorectal carcinoma) 116 cells, albeit with less electrostatic binding affinity for the cells. Moreover, the transfection efficiency in the HCT 116 cells was higher than that in the HEK 293 cells under the same conditions, which may be due to the target bonding affinity of the RGD peptides in ASF for integrins on the HCT 116 cell surface. This result indicated that the RGD binding affinity in ASF for integrins can enhance the specific targeting affinity to compensate for the reduction in electrostatic binding between ASF-coated PEI carriers and cells. Cell viability measurements showed higher cell viability after transfection of ASF/PEI/DNA ternary complexes than after transfection of PEI/DNA binary complexes alone. Lactate dehydrogenase (LDH) release studies further confirmed the improvement in the targeting effect of ASF/PEI/DNA ternary complexes to cells. These results suggest that ASF-coated PEI is a preferred transfection reagent and useful for improving both the transfection efficiency and cell viability of PEI-based nonviral vectors.     

Polymeric pH-sensitive membranes—A review

Significant progress has been achieved in recent years in the field of pH-sensitive membranes. In many cases, pH-sensitive membranes are systems for which the flux, membrane pore size, and solute rejection ratio may be manipulated by changing the pH. This review summarizes recent developments covering the preparation, pH-responsive properties, and applications in various disciplines. The pH-sensitive groups and the evaluation parameters for pH-sensitive membranes are reviewed and discussed. A variety of preparation methodologies, including blending, pore-filling, surface-grafting, and surface-coating techniques are described, and some of their salient features are highlighted. The flat-sheet form and hollow-fiber form pH-sensitive membranes are reviewed. Membrane pore size change and electroviscous effect are discussed. Furthermore, future perspectives of pH-sensitive membranes are discussed.     

Simultaneous Recovery of Nickel and Cobalt from Aqueous Solutions using Complexation-Ultrafiltration Process

Simultaneous recovery of nickel and cobalt from aqueous solutions by complexation-ultrafiltration process with polyethylenimine (PEI) was studied. Experiments were performed as a function of polymer/metal ratio (P/M), solution pH, and ionic strength. Effects of concentration time on metal rejection and membrane flux were also studied. At optimum experimental conditions of pH 6.0 and P/M 5.0, the nickel removal efficiency reaches at 99.9% and cobalt removal efficiency goes to 96.4%. Both nickel and cobalt removal efficiencies decreased as the adding salt concentration increases. During 12 h of the ultrafiltration process, the decline of membrane flux was less than 16% and the removal efficiencies for both nickel and cobalt were kept almost constant. Diafiltration was further performed to regenerate PEI. The removal efficiencies for both metals using recycled PEI were found to be close to those with the original PEI. Results from the two-step process of complexation-UF and decomplexation-UF separation showed that it could be a promising method for simultaneous recovery of nickel and cobalt from aqueous solutions.     

Efficient mAb production in CHO cells incorporating PEI‐mediated transfection,mild hypothermia and the co‐expression of XBP‐1

BACKGROUND: Transient gene expression (TGE) provides a rapid way to generate recombinant protein biologics for pre‐clinical assessment. Human embryonic kidney (HEK293) cells have traditionally been used for TGE; however, there is demand from industry for efficient, high‐producing TGE systems that utilize Chinese hamster ovary (CHO) cells. A polyethyleneimine (PEI) ‐based TGE process has been developed for CHO cells using an episomal expression system to generate enhanced recombinant protein titers. RESULTS: A five‐fold improvement in monoclonal antibody (mAb) volumetric productivity was achieved by examining key parameters including transfection medium, cell density, transfection reagent, DNA:reagent ratio, the time of transfer to mild hypothermia and feeding strategy post‐transfection. The Epi‐CHO system allowed for a six‐fold expansion in culture volume post‐transfection without significantly affecting specific productivity. This system generates 400% more mAb per µg of plasmid DNA when compared with a non‐episomal system. In addition, the use of X‐box binding protein 1 to enhance secretion capacity and provide further improvements in mAb production with TGE was investigated. CONCLUSION: Through optimization of key parameters, our results demonstrate the development of a low‐cost, high‐yielding, episomal TGE system that may be adopted during pre‐clinical biologic drug development. Copyright © 2011 Society of Chemical Industry     

Improved Preparation Method of Polyethylenimine-Hydroxyapatite and Its Chromatographic Properties

Previously, we developed polyethylenimine-coated hydroxyapatite as a chromatography medium. This report describes a simple, safe, productive, and improved preparation method and reports further chromatographic properties. The improved polyethylenimine-coated hydroxyapatite was prepared by use of a rotary evaporator with neither decantation, cross-linking agent, nor organic solvent. In chromatography, ovalbumin (a phosphoprotein) was separated from other proteins. Furthermore, ovalbumin derivatives or nucleotides could be separated on the basis of the number of phosphate residues. This method yielded high-quality and -quantity polyethylenimine-coated hydroxyapatite.     

Real-time gene delivery vector tracking in the endo-lysosomal pathway of live cells

Using live-cell confocal microscopy and particle tracking technology, the simultaneous transport of intracellular vesicles of the endo-lysosomal pathway and nonviral polyethylenimine (PEI)/DNA nanocomplexes was investigated. Due to potential problems associated with the use of acid-sensitive probes in combination with a gene vector that is hypothesized to buffer the pH of intracellular vesicles, the biological location of PEI/DNA gene vectors was revealed by probing their trafficking in cells expressing fluorescent versions of either early endosome antigen 1, a protein that localizes to early endosomes, or Niemann Pick C1, a protein that localizes to late endosomes and lysosomes. Studies directly show that PEI/DNA nanoparticles are actively transported within both early and late endosomes, and display similar overall transport rates in each. Additionally, gene vector transfer between endosomes is observed. Over time post-transfection, gene vectors accumulate in late endosomes/lysosomes; however, real-time escape of vectors from membrane-bound vesicles is not observed.     

Polymer assisted ultrafiltration for copper–citric acid chelate removal from wash solutions of contaminated soil

The removal of heavy metals from aqueous systems such as wash-solutions of contaminated soil by using Polymer-Assisted Ultrafiltration (PAUF) has been studied. For the extraction of metal ions from contaminated soil citric acid is used as a chelating agent. Cu²⁺ as metal ion and the polymer polyethylenimine (PEI) as ligand were used in the various experiments. Optimal chemical conditions for copper complexation by citric acid were determined by means of complexation tests. The results showed that citric acid is able to chelate copper ions at pH 5.5, while decomplexation occurs at pH 2. Maximum bonding capacity (saturation condition) was 0.625 mg Cu²⁺ per mg citric acid, meaning 2 mol Cu²⁺ per mol citric acid. Complexation tests in the system polyethylenimine–citric acid–copper showed that the polymer is able to complex the copper–citric acid chelate at pH = 6 while release occurs at pH < 3. The saturation condition was 0.333 mg Cu²⁺ per mg PEI. The ultrafiltration tests, carried out at three trans-membrane pressures (2, 3 and 4 bar), showed the possibility of using the PAUF technique for copper ion removal from aqueous solutions.     

Boric acid binding studies with diol containing polyethylenimines as determined by 11B NMR spectroscopy

Three water‐soluble polymers incorporating increasing levels of 2,3‐dihydroxy propyl attached to polyethylenimine (PEI) backbone were synthesized, characterized by NMR, and investigated for their ability to bind boric acid (BA). ¹¹B NMR spectroscopy showed that BA interacted with the polymeric 2,3‐dihydroxy propyls by forming borate monoester and borate diesters in the boron concentration range of 100–1000 ppm and at 0.0775M polymer. Borate monoester species predominated for low functionalization levels (33% of the PEI amines functionalized), whereas borate diester species dominated for the higher functionalized polymers (66–100% of the PEI amines functionalized). All three polymers showed that 100% of the BA was bound as a mixture of borate mono‐ and diesters at 100‐ppm boron. The overall best performer based on total borate ester formation was the 2/3‐PEI, with a binding K_d of 631 at 200 ppm boron. Borate ion concentration was measured from the ¹¹B NMR chemical shift of the BA/borate peak and it decreased as 1/3‐PEI > 2/3‐PEI > 3/3‐PEI. Variable temperature ¹¹B NMR showed drastic reduction of borate ester species at 65°C. Thus, PEI polymers, as the ones investigated in this work, are reasonable candidates for the selective recovery and recycle of BA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4411–4418, 2006