Amount Of Polyethyleneimine Research Articles

Purification of polyethylenimine polyplexes highlights the role of free polycations in gene transfer.

Nonviral vectors based on polyethylenimine (PEI) usually contain an excess of PEI that is not complexed to DNA. Since unbound PEI contributes to cellular and systemic toxicity, purification of polyplexes from unbound PEI is desirable. Size exclusion chromatography (SEC) was used to purify PEI polyplexes of free PEI. Transfection properties of purified polyplexes and the effect of free PEI on gene delivery were studied in vitro and in vivo after systemic application into mice. SEC did not change the size and zeta-potential of polyplexes. Independent of the amount of PEI used for complex formation, purified PEI polyplexes had the same final PEI nitrogen/DNA phosphate ratio of 2.5. Notably, purified PEI polyplexes demonstrated low cellular and systemic toxicity. High transfection efficiency was achieved with purified polyplexes at high DNA concentrations (8-15 microg/ml). At low DNA concentrations (2-4 microg/ml) gene transfer with purified particles was less efficient than with polyplexes containing free PEI both in vitro and in vivo. Mechanistic studies showed that free PEI partly blocked cellular association of DNA complexes but was essential for the following intracellular gene delivery. Adding free PEI to cells treated with purified particles with a delay of up to 4 h resulted in significantly enhanced transfection efficiency compared with non-purified particles or purified particles without free PEI. This study presents an efficient method to remove free PEI from PEI polyplexes by SEC. Our results from transfection experiments demonstrate that free PEI substantially contributes to efficient gene expression but also mediates toxic effects in a dose-dependent manner. Purified polyplexes without free PEI have to be applied at increased concentrations to achieve high transfection levels, but exhibit a greatly improved toxicity profile.

Preparation and performance of cellulose acetate/polyethyleneimine blend microfiltration membranes and their applications

A modified microfiltration membrane has been prepared by blending a matrix polymer with a functional polymer. Cellulose acetate (CA) was blended with polyethyleneimine (PEI), which was then crosslinked by polyisocyanate, in a mixture of solvents. In the membrane, PEI can supply coupling sites for ligands in affinity separation or be used as ligands for metal chelating, removal of endotoxin or ion exchange. The effects of the time of phase inversion induced by water vapor, blended amount of PEI and amount of crosslinking agent on membrane performance were investigated. The prepared blend membranes have specific surface area of 12.04–24.11 m 2/g and pure water flux (PWF) of 10–50 ml/cm 2 min with porosity of 63–75%. The membranes, made of 0.15 50 wt.% PEI/CA ratio and 0.5 crosslinking agent/PEI ratio, were applied to adsorbing Cu 2+ and bovine serum albumin (BSA) individually. The maximum adsorption capacity of Cu 2+ ion on the blend membrane is 7.42 mg/g dry membrane. The maximum adsorption capacities of BSA on the membranes with and without chelating Cu 2+ ion are 86.6 and 43.8 mg/g dry membrane, respectively.

Influence of polyethylenimine on the precipitation process of lead sulfate crystals

Crystals of lead sulfate were precipitated in a solution of polyethylenimine (PEI) using a double-jet crystallizer. PEI controlled both the nucleation rate and the growth rate, and enabled to produce fine monodispersed crystals. This effect is considered to be due to a complexation between PEI and lead ion. The on-line measurement of the variation in the lead ion concentration indicated PEI lost its effect when a certain amount of reactants was supplied. And the duration in which PEI could control the precipitation rate and the amount of PEI had a strong correlation. In addition, it was suggested that their relationship could be utilized in order to produce monodispersed particles.

DNA Vector Polyethyleneimine Affects Cell pH and Membrane Potential: A Time-Resolved Fluorescence Microscopy Study

Polyethyleneimine (PEI) is one of the very efficient nonviral vectors being developed and tested for artificial gene transfer into target cells. One of its serious limitations is the significant cytotoxicity of the large amounts of free PEI in the mixtures of DNA and PEI used for transfection. To further investigate the cellular effects of free PEI, we have analyzed the PEI-induced alterations of various cell parameters such as membrane heterogeneity and fluidity, cytoplasmic pH, and plasma membrane potential in a variety of cells such as Swiss 3T3 fibroblast, Chinese hamster ovary, insect cells SF9, plant cell line BY2, and Saccharomyces cerevisae. Fluorescence probes such as Nile red, SNARF-1, and cyanine dye DiSC2(3), coupled with the technique of picosecond time-resolved fluorescence microscopy, were used in estimating the above-mentioned cell parameters. It was found that the cell membranes were largely unperturbed by PEI. However, the cytoplasmic pH showed an increase of ∼0.1–0.4 units when the cells were treated with PEI. The plasma membrane potential was found to be depolarized in S. cerevisae and Swiss 3T3 cells. These results suggest that the cytotoxic effects of PEI may partly originate from inhibition of regulation of cytoplasmic pH and plasma membrane potential. Further, it is proposed that the resultant cell alterations favors the transfection process.

Spectrophotometric determination of polyethylenimine in the presence of an oligonucleotide for the characterization of controlled release formulations

Polyethylenimine (PEI) is a cationic polymer that can be associated to oligonuclotides to promote their transfection both in vitro and in vivo. The controlled release of oligonucleotide/polyethylenimine complexes from biodegradable systems can result in an increased cellular internalisation of the oligonucleotide and a reduced cytotoxicity of the complex. This effect strongly depends on the amount of PEI loaded in and released from the delivery system. In this work we describe a rapid, sensitive and reproducible spectrophotometric method for the quantitative analysis of PEI by itself or in the presence of an associated oligonucleotide. PEI does not possess chromophores, hence the determination by ordinary spectrophotometry is not possible. However, upon addition of copper (II) ions, PEI forms a dark blue cuprammonium complex that can be detected by UV-vis spectrophotometry. The optimum conditions in terms of optical parameters, copper (II) concentration required for a quantitative PEI complexation, and the most suitable medium for the reaction were ascertained. A linear relationship ( r 2=0.9997) between absorbance and amounts of PEI was found at λ max of 285 nm over the concentration range 5.0–50.0 μg ml −1. The detection limit (QOD) was 4.0 μg ml −1. The method was validated for the quantitation of PEI in the presence of an oligonucleotide, which absorbs at 285 nm as well.

Synthesis, Characterization, and Biocompatibility of Polyethylenimine-graft-poly(ethylene glycol) Block Copolymers

Two series of block copolymers were prepared by grafting linear poly(ethylene glycol) (PEG) onto branched polyethylenimine (PEI). In the first series, the PEI (25 000) was grafted with varied numbers of PEG blocks (5000). The second series was composed of copolymers all containing an equal amount of PEG (50%) and PEI (50%), but with PEG of different molecular weights (MW: 550−20 000). In a two-step synthesis, both the activation of monomethyl-PEGs and the coupling reactions of the PEGs with PEI were performed with hexamethylene diisocyanate (HMDI), leading to water-soluble copolymers with hydrolytically stable urethane and urea bonds. The molecular structure of the resulting copolymers was evaluated spectroscopically (NMR, FTIR). Thermal and calorimetric analysis (TGA, DSC) as well as size exclusion chromatography (SEC) verified the successful formation of the copolymers. MW was determined by static light scattering in combination with SEC. With respect to their application as gene transfer agents, the biocompatibility of the copolymers was studied using an in vitro cytotoxicity assay (lactate dehydrogenase assay) and blood compatibility tests (hemolysis and erythrocyte aggregation). It was found that PEG reduced the toxicity of PEI and prevented hemolysis as well as the aggregation of erythrocytes. The extent of the positive influence of PEG on the biocompatibility of the copolymers was found to be dependent upon both the number of PEG blocks and the structure of the block copolymers.

Preparation of Thick Silica Films by the Electrophoretic Sol-Gel Deposition Using a Cationic Polymer Surfactant

Thick silica films were prepared on the cathode by the electrophoretic sol-gel deposition using a cationic polymer surfactant, polyethylenimine (PEI). The weight of the silica particles deposited on the cathode was maximized when the content of PEI added was 0.01mass% and pH of the coating sols was 5. As the amount of PEI added increased over the optimum content (0.01mass%), the weight of the silica particles deposited decreased with an increase in PEI content because of H2 generation at the cathode and the aggregation and precipitation of silica particles in the coating sols. Thick silica films obtained had no cracks and the thickness was ca. 20μm.

Modification of Transport Properties of Ion Exchange Membranes.XV. Preparation and Properties of Cation Exchange Membranes Having a Single Cationic Charged Layer on the Membrane Surface by Sulfonyl–Amide Bonding

Abstract In order to prepare an excellent monovalent cation permselective cation exchange membrane, a polyethyleneimine (PEI) layer was formed with sulfonyl–amide bonding between PEI and sulfonyl chloride groups on one surface of the membrane. Two methods were tried: 1) one surface of the membrane reacted with PEI and the remaining sulfonyl chloride groups were hydrolyzed, and 2) after one surface of the sulfonyl chloride groups had been hydrolyzed, the other surface of the membrane was reacted with PEI and the remaining sulfonyl chloride groups were hydrolyzed. The cation exchange membranes, which had been prepared using both methods, had excellent monovalent cation permselectivity, low electrical membrane resistance and high current efficiency for the long-term electrodialytic concentration of seawater. The reacted amount of PEI on the membrane was about 10% of the cation exchange capacity.

Protonation of Polyethylenimine

Abstract Protonation of polyethylenimine (PEI) has been studied by various investigators [1–41. Most studies involved potentiometric titrations with hydrochloric acid and the effect of added salts. Liu [51 has reported the specific influence of chloride, bromide, and nitrate ions on the viscosity of solutions of protonated PEL It has been noticed that, when a small amount of PEI is added to ammonium nitrate, gaseous ammonia is produced. No information, however, has been found concerning the quantitative basis of the reaction. The study of the quantitative nature of protonated PEI by various reagents is reported in this note. In general, agreement with previous work is excellent. It also shows slight variation on the degree of protonation by various reagents.