High Molecular Weight Polyethyleneimine Research Articles

Modulating nanocellulose hydrogels and cryogels strength by crosslinking and blending

The mechanical strength of hydrogels and cryogels made from carboxylated nanocellulose (NC) fibers can be modulated by chemically/physically crosslinking and blending with different fibrils (shorter/longer). Nanocellulose hydrogels are produced by oxidizing Bleached Eucalyptus Kraft (BEK) pulp followed by high pressure mechanical treatment. Polyethyleneimine (PEI) and hexamethylenediamine (HMDA) were selected to crosslink nanocellulose hydrogels physically and chemically, respectively. Shorter cellulose nanocrystals (CNC) and longer microcrystalline cellulose (MCC) fibrils were blended with the TEMPO oxidized nano/micro fibers to produce hydrogels of controlled properties. Nanocellulose cryogels were prepared from these hydrogels by a two steps process of freezing and lyophilization. The mechanical properties of nanocellulose hydrogels and cryogels were modulated by controlling the type and density of crosslinking as well as by blending with nano- or microfibrils. Chemical crosslinking (HMDA) increases the hydrogel elastic compression moduli (G′) but does not significantly affect the compressive strength of the cryogel. SAXS reveals the HMDA crosslinked hydrogel to be structurally homogeneous. Physical crosslinking with high molecular weight PEI increases the storage modulus (G′) of nanocellulose hydrogels. Blending a carboxylated nanocellulose fiber suspension with CNC significantly increases the cryogel compressive strength. Nanocellulose gel exhibits tuneable mechanical strength and absorption capacity from the crosslinking/blending strategy (type and density); this improved fundamental knowledge of the fiber-crosslinker and fiber-cellulose crystal interactions enables greater control and tunability of the properties of hydro- and cryogels for personal and infant care products, as agricultural water retention aids, and for biosensor applications.

Removing free-floating oil from water using cationic polymers/surfactant-modified silica

Abstract The purpose of this work was to evaluate the efficiency of oil sorption of silica particles modified by three different types of cationic polymers and a cationic surfactant. Low-molecular-weight polyethyleneimine (LPEI), high-molecular-weight polyethyleneimine (HPEI), polydiallyldimethylammonium chloride (PDM), and cetyltrimethylammonium bromide (CTAB) were used to modify the silica particles and then compared their performances for oil removal. The scanning electron microscope and zeta potential measurements were used to analyze the surface characteristics of unmodified and modified silica particles. Adsorptions of motor oil and palm oil on the modified silica particles have been investigated under various parameters such as the silica particle size, the oil concentration, the polymer/surfactant concentrations, and the pH. The results have shown that the modified silica particles enhanced the oil sorption ability by approximately 10–20 times depending on the size of silica particles, pH, and the type of polymer/surfactant used when compared with the unmodified silica particles. The highest palm oil adsorption values of LPEI-silica, HPEI-silica, PDM-silica, CTAB-silica, and unmodified silica were 2.40, 2.10, 1.95, 1.50, and 0.15 g/gsilica, respectively. Moreover, the oil sorption of the modified silica particles was increased by approximately 30–50% for the smallest-sized silica particles.

Synthesis of articular cartilage‐inspired branched polyelectrolyte polymer for enhanced lubrication

The superlubrication property of articular cartilage is attributed to the hydration lubrication mechanism. This involves the complexation of biomacromolecules with phosphatidylcholine lipids to form a lubricating boundary layer on the surface. Based on this mechanism, a branched polyelectrolyte polymer – PEI-PMPC was synthesised in this study to enhance lubrication via tert-butyl hydroperoxide-initiated grafting polymerisation of 2-methacryloyloxyethyl phosphorylcholine (MPC) onto polyethyleneimine (PEI) with various molecular weights. Following the characterisation of the polymer using nuclear magnetic resonance, a series of tribological tests were performed under different normal loads and different scan rates. The results showed that the PEI-PMPC polyelectrolyte polymer in aqueous solution could effectively reduce the friction coefficient and wear generation between the polyethylene ball and the silica wafer. Additionally, an improvement in the lubrication performance was detected for the PEI-PMPC polyelectrolyte polymer when high molecular weight PEI was used during the reaction, which was attributed to the formation of the hydration shells surrounding the zwitterionic charges of PMPC and the viscosity of the polymer. In conclusion, the PEI-PMPC polyelectrolyte polymer developed herein was characterised by enhanced lubrication, and may be potentially used for biomedical applications such as intra-articular injection to restore joint lubrication.

Polyethyleneimine-stabilized palladium nanoparticles for reduction of 4-nitrophenol

Palladium nanoparticles (Pd NPs) have been drawing great interest as catalysts for water treatment. Herein, high molecular weight polyethyleneimine (PEI) (molecular weight: 70 kDa) was used as template to stabilize Pd NPs. PEI was incubated with disodium tetrachloropalladate, followed by reduction with sodium borohydride. Pd NPs had narrow size distribution with diameter from 3.64 to 6.20 nm. The PEI-stabilized palladium nanoparticles (Pdn-PEI NPs) showed excellent long-term stability and positive zeta potential in phosphate saline buffers with different pH values. In addition, Pdn-PEI NPs exhibited high efficiency for catalysis of 4-nitrophenol (4-NP) in aqueous solution. The catalytic reduction of 4-NP followed the pseudo-first-order behavior, which had the highest catalytic ability (knor = 229). The enhanced properties can be attributed to the high stability and smaller size of Pdn-PEI NPs in aqueous solution, resulting from the application of PEI template. This method can be used to prepare highly stable metal nanoparticles with potential applications in catalysis of polluted water in the future.

Conformation and activity alteration of horseradish peroxidase induced by the interaction with gene carrier polyethyleneimines

Polyethyleneimine (PEI) has long been considered as “golden standard” for polymeric gene delivery carriers. However the molecular basis of the cytotoxicity of PEI is poorly understood. Little is known about the effects of PEI on the structure and functions of biomacromolecules. In this work, fluorescence, UV–vis absorption, circular dichroism spectroscopy were conducted to investigate the influence of PEI of average molecular weight 25, 10 and 1.8kDa (denoted as PEI25k, PEI10k and PEI1.8k) on the conformation of horseradish peroxidase (HRP) and its catalytic efficiency. Zeta-potential measurement and isothermal titration calorimetry were used to reveal the mechanism of the interaction between PEIs and HRP. PEIs were found to bind onto the surface of HRP predominantly via hydrophobic interaction and hydrogen bond or van der Waals interaction. The complex formation between HRP and PEI induced a more compact conformation of the enzyme and an increased hydrophobicity of the microenvironment surrounding heme pocket. The conformational change of HRP had little impact on the affinity towards H2O2 and phenol. However, the increase in the non-planarity of porphyrin ring in the heme group led to an increase in the exposure degree of the active center and thus an enhancement of catalytic efficiency of HRP in the presence of high molecular weight PEIs (PEI25k and PEI10k). The polymer size played an important role in PEI-HRP interaction. PEI of low molecular weight (PEI1.8k) was less efficient to alter the conformation and catalytic activity of HRP in aqueous solutions.

Designing of dynamic polyethyleneimine (PEI) brushes on polyurethane (PU) ureteral stents to prevent infections

Permanent antibacterial coatings have been developed by brush-like polyethyleneimine (PEI) on polyurethane (PU) ureteral stents since bacterial adhesion and biofilm formation with the following encrustation on stent surface limit their long term usage. In order to control or prevent bacterial infections; PEI chains with two different molecular weights (Mn: 1800 or 60,000Da) were covalently attached on the polyurethane (PU) surface by “grafting to” approach to obtain a brush-like structure. Then, PEI brushes were alkylated with bromohexane to enhance the disruption of bacterial membranes with increasing polycationic character. X-ray Photoelectron and Infrared Spectroscopy investigations confirmed that PEI grafting and alkylation steps were performed successfully. Surface roughness in dry state increased dramatically from 65.8nm to 277.7nm and 145.2nm for short chain PEI and long chain PEI grafted samples, respectively. Both low and high molecular weight PEI grafts exhibited a brush-like structure and potent antibacterial activity by lowering the adherence of Klebsiella pneumonia, Escherichia coli and Proteus mirabilis species up to two orders of magnitude without any cytotoxic effect on L929 and G/G cells. Thus, permanent bactericidal activity was achieved by the contact-active strategy of dynamic PEI brush-like structures on polyurethane ureteral stent.

A review of the developments of characteristics of PEI derivatives for gene delivery applications

ABSTRACTRedox‐active stimuli have gained a great deal of interest as an indicating factor for designing bioresponsive matrices in gene delivery. Hence, a wide range of gene carriers has been designed incorporating the redox‐stimuli characteristics. The most important type of gene carriers is the class of redox responsive polymers. Among them, disulfide incorporated redox‐responsive polyethyleneimine (PEI) and its derivatives, as a result of their outstanding DNA entrapping characteristics and their intrinsic endosomolytic activity, have attracted considerable attention in recent studies. The review presents the main developments of the characteristics of PEI derivatives and their applications in gene delivery. It is found that despite the uniquely stated characteristics, the noncleavable structure of conventional PEI (high molecular weight PEI: 25k), which makes it a nondegradable material, as well as the frequent inclusion of positively charged amino groups, which reduces its blood circulation period, render conventional PEI a very toxic material for gene‐delivery applications. The extremely high cellular toxicity of conventional PEI has restricted its administration for real in‐vivo physiological media. Recent studies have shown that employing low molecular weight PEI cross‐linked by disulfide linkages (SS‐PEI) and assembling low molecular weight disulfide linkages PEI (LMW SS‐PEI) with bio‐detachable anionic groups were two successful approaches for increasing bioavailability of the PEI‐based gene carriers, while keeping outstanding cellular transfection. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42096.

A releasable disulfide carbonate linker for polyethyleneimine (PEI)-based gene vectors

In this study, a releasable disulfide carbonate linker is used to prepare disulfide-containing crosslinked polyethyleneimines (PEI-SS-CLs) for gene delivery. ESI-MS analysis shows that after being incubated with 1,4-dithio-DL-threitol (DTT), the degradable linkages in the polyethyleneimine (PEI) derivatives undergo disulfide bond cleavage followed by intramolecular cyclization and cleavage of the neighboring carbamate bond. Moreover, it is observed that thiol/polyanions trigger the release of DNA from polyplexes via the reductive degradability of PEI-SS-CLs and ion-exchange. In vitro transfection results indicate that PEI-SS-CL-1.5 (at a crosslinker/PEI feed molar ratio of 1.5) exhibits higher transfection efficacy than the commercially available reagents such as the high molecular weight PEI with a molecular weight of 25 kDa (PEI 25k) and the versatile liposomes Lipofectamine 2000. PEI-SS-CL-1.5 also demonstrates significantly lower cytotoxicity, compared with PEI 25k and Lipofectamine 2000. Our study indicates that incorporating the thiol-specific cleavable disulfide bond into crosslinked PEIs and implementing regulated release of DNA are effective strategies for designing safe and effective gene vectors.

Polyethyleneimine‐poly(ethylene glycol)‐star‐copolymers as efficient and biodegradable vectors for mammalian cell transfection

High molecular weight (MW) polyethyleneimine (PEI) has been successfully used for the transfection of a broad variety of cell lines. In contrast to low MW PEI, which exhibits low transfection efficiencies but also low cytotoxicity, high MW PEI-mediated transfection achieves much higher efficiencies but at the cost of cell viability; therefore its use in commercial scale transfection and clinical application is limited. In this work we address this problem by constructing biodegradable high MW PEI mimics built from low MW PEI building blocks. The end-groups of small 5-arm star polyethylene glycol (PEG) prepolymers were decorated with linear oligo-ethyleneimine (OEI)/PEI arms of various MW via azomethine linkages. The resultant PEI-PEG-star-copolymers were investigated for their ability to complex plasmid DNA. Polymer/DNA complexes were characterized using techniques such as dynamic light scattering and transmission electron microscopy. Having established their cytotoxicity limits, they were tested as gene delivery vehicles for the transfection of suspension adapted Chinese hamster ovary (CHO-S) cells under serum-free conditions and adherent human embryonic kidney cells (HEK293T) in serum containing medium. Our PEI-PEG-star-copolymers showed a reduced cytotoxicity compared to high MW PEI while maintaining the ability to complex plasmid DNA and transfect mammalian cells, with significant transfection efficiencies. The effects of the optimum parameters on the transfection of mammalian cells using such novel polymers are discussed.

Unique concentration dependence on the fusion of anionic liposomes induced by polyethyleneimine

We investigated the interaction of branched polyethyleneimine (PEI) with anionic vesicles formed with 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) by spectroscopic measurements and microscopic observations. PEI induced the fusion of the vesicles only over a specific concentration range, which was found to be below the transition of vesicular zeta-potential from negative to positive value. Above the concentration window of membrane fusion, charge inversion of DOPS vesicles due to the further adsorption of PEI onto the surface of vesicle, inhibited the membrane fusion events. The PEI with low molecular weight induced the membrane fusion in a wider range of concentration than high molecular weight PEIs. Our results suggest that the mechanism of PEI interaction with the lipids depends on the molecular weight and stoichiometry of the polycation to negatively charged lipids.

Deactivation Efficiency of Stabilized Bactericidal Emulsions

Biocide emulsions stabilized with various stabilizing agents were prepared and characterized, and their efficiency in bacteria deactivation was evaluated. A number of stabilizing agents were tested for their stabilizing effect on emulsions of thiocyanomethylthiobenzothiazole (TCMTB) biocide. Two agents, the most successful in stabilizing the biocide, were chosen for further studies: high molecular weight polyethyleneimine (PEI) and an amphiphilic block copolymer of poly(caprolactone)-b-poly(acrylic acid) (PCL(33)-b-PAA(33)). The emulsion droplet sizes varied between 325 and 500 nm. Deactivation of bacteria was studied by exposing E. coli ATCC 11229 bacteria dispersions to emulsions stabilized by positively charged PEI or negatively charged PCL-b-PAA micelles and by measuring their absorbance; E. coli do not grow with time in the presence of biocide emulsions. PEI molecules alone act as biocide and deactivate the bacteria. PCL-b-PAA micelles as stabilizing agent do not affect the growth of the E. coli ; bacteria are deactivated by TCMTB released from the emulsion droplets. The kinetics of emulsion dissolution studies revealed for both stabilizing agents a decrease in droplet size with time while the emulsions were subjected to dialysis. The biocide was released from the emulsions within ∼250 min; the droplet shells consist mostly of PEI or PCL-b-PAA insoluble complexes with the biocide, which do not dissolve during dialysis. SEM images confirm the presence of residual crumbled shells with holes after 24 h of dialysis.

Hyperbranched Polyethyleneimine Induced Cross-Linking of Polyamide−imide Nanofiltration Hollow Fiber Membranes for Effective Removal of Ciprofloxacin

This study aims to develop a positively charged nanofiltration (NF) hollow fiber membrane for effective removal of ciprofloxacin from water. A novel NF membrane was fabricated by hyperbranched polyethyleneimine (PEI) induced cross-linking on a polyamide-imide hollow fiber support. The spongy-like, fully porous membrane support provides minimal transport resistance and sufficient mechanical strengths for water permeation under high pressures. It is found that the PEI modification significantly influences NF performance through the mechanisms of size exclusion, charge repulsion, and solute-membrane affinity. Specifically, after PEI induced cross-linking, the membrane pore size is significantly reduced. The membrane surface becomes more hydrophilic and positively charged. As a result of these synergic effects, the rejection of ciprofloxacin is substantially enhanced. Furthermore, experimental results show that the molecular weight of PEI has tremendous effect on NF performance of the as-modified membrane. The NF membrane modified by a high molecular weight PEI_60K exhibits the highest rejection, the lowest fouling tendency, and keeps a constant flux over the whole pH range. This study may have great potential for developing high-performance antifouling NF hollow fiber membranes for various industrial applications.

Interaction between silica in the presence of adsorbed poly(ethyleneimine): correlation between colloidal probe adhesion measurements and yield stress

The interaction forces between silica surfaces with adsorbed layers of polyethyleneimine (PEI) were measured using colloidal probe microscopy as a function of solution conditions and PEI molecular weight. The surface coverage of polymer, as determined from optical reflectometry, was a significant factor influencing the extension of the chains away from the interface and also the development of adhesion between the surfaces. For the high molecular weight PEI (70 kDa), the adhesion passed through a maximum as a function of pH. The magnitude and position of this maximum was dependent on the surface excess of adsorbed PEI. The greatest adhesion was observed for the highest surface coverage of 0.88 mg m(-2) at pH 11 where the force-distance curves on approach indicated the presence of a significant steric layer. Furthermore, the forces on separation under these conditions indicated strong bridging of PEI chains across the interface contributing to the enhanced adhesion. However, at lower surface coverage, no bridging was observed but the adhesion was still significantly greater than in the absence of an adsorbed layer of PEI. The adhesion at lower surface coverage was indicative of a charge-patch mechanism. The measured values of adhesion correlated very well with the observed yield stress of concentrated dispersions of silica in the presence of adsorbed layers of PEI. Thus, the molecular mechanisms probed during surface forces measurements can be used to predict the ensemble behaviour of the many particles dispersed in an aqueous medium which is of particular importance in minerals processing.

Synthesis, Characterization, and Carbon Dioxide Adsorption of Covalently Attached Polyethyleneimine-Functionalized Single-Wall Carbon Nanotubes

The reaction between fluorinated single-wall carbon nanotubes (F-SWNTs) and branched (M(w) = 600, 1800, 10000, and 25000 Da) or linear (M(w) = 25000 Da) polyethyleneimine (PEI) yields the covalent attachment of the polymer to the sidewalls of the nanotubes. The resulting PEI-functionalized SWNTs (PEI-SWNTs) were characterized by solid-state (13)C NMR, Raman spectroscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, atomic force microscopy, transmission electron microscopy, and thermal gravimetric analysis studies. As expected, the number of polymer molecules per SWNT is larger for low molecular weight PEI than for high molecular weight PEI. However, above 1800 Da, the number of polymer molecules per SWNT does not vary as much. This is supported by Raman spectral data that shows the D:G ratio is relatively insensitive of the molecular weight for M(w) > 1800 Da. The PEI-SWNTs are shown to have solubility in aqueous media of up to 0.4 mg x mL(-1). Solid-state (13)C NMR shows the presence of carboxylate substituents that have been attributed to carbamate formation as a consequence of the reversable CO(2) absorption to the primary amine substituents of the PEI. Desorption of CO(2) is accomplished by heating under argon at 75 degrees C, while the dependence of the quantity of CO(2) absorbed on temperature and the molecular weight of the PEI is reported. Under the conditions investigated the maximum absorption of 9.2% w/w is observed for PEI(25000)-SWNT at 27 degrees C. The possible CO(2) absorption applications of the PEI-SWNTs is discussed.

Polyethyleneimine (PEI) functionalized ceramic monoliths as enzyme carriers: Preparation and performance

Classical cordierite monoliths and acicular mullite (ACM) monoliths were used as support material for ionic adsorption of β-galactosidase from Aspergillus oryzae. Monoliths were silica-coated, then functionalized with polyethyleneimine (PEI) using different methods. In addition to direct adsorption of PEI, monoliths were modified with (3-glycidoxypropyl)trimethoxysilane (GPTMS) and γ-(aminopropyl)triethoxysilane (APTES)–glutaraldehyde for covalent attachment of the polymer. The optimal method, in terms of immobilization capacity and stability, was selected by using a particulate silica support and crushed monoliths. Immobilization of PEI via a GPTMS-functionalized ACM monolith yields the best enzyme carrier. At pH 7, 150 mg β-galactosidase g −1 SiO 2 can be adsorbed. In general, a coating with a higher molecular mass polymer results in stronger immobilization, at a higher rate. By using whole monoliths, we find that the molecular weight of the polymer coating influences the adsorption/desorption of the enzyme. The open walls of the ACM monoliths permit significant higher loadings of high molecular weight PEI, which results in a higher enzyme-support strength and increased stability with respect to enzyme desorption. These PEI systems provide an optimal environment for the β-galactosidase, 92% of the free enzyme activity is retained after immobilization. Although adsorption was quite strong and permitted the use of the immobilized enzyme in a wide range of conditions, the enzyme could be completely desorbed after its inactivation. The monolith-carrier combination can be reused several times.

Impregnation of palm shell activated carbon with polyethyleneimine and its effects on Cd 2+ adsorption

Palm shell activated carbon (AC) was impregnated with low (LMW) and high molecular weight (HMW) polyethyleneimine (PEI) via batch adsorption. The maximum amount of LMW PEI adsorbed on AC was determined to be approximately 425 mg/g carbon while the maximum adsorbed HMW PEI was 2.8 mg/g carbon. The LMW PEI adsorption data fitted the Langmuir isotherm better than the Freundlich isotherm. The PEI impregnated AC were characterized via nitrogen adsorption, scanning electron microscopy, elemental analysis, thermogravimetric, Fourier transform infra red and pH drift analyses. Only LMW PEI could be successfully impregnated as monolayers on the surface of the micropores. This impregnation leads to drastic reduction of surface area and pore volume whereas impregnation of HMW PEI does not significantly affect the physical characteristics of the AC. LMW PEI impregnation appears to enhance Cd 2+ adsorption capacity of the AC while HMW PEI impregnation is found to have an opposite effect. This result shows that LMW PEI impregnation technique may have the potential to improve the batch adsorption capacity of AC for other transition metal ion adsorption as well.

Protein stabilising effect of polyethyleneimine

The effect of polyethyleneimine (PEI), a cationic polymer, on protein stability was investigated. Shelf stability of lactate dehydrogenase, stored as an aqueous solution, at 36°C was distinctly improved in the presence of 0.01–1% (w/v) polymer (except at pH 5.0). PEI also prevented aggregation of the protein during long-term storage. Both high and low molecular weight (ca. 600 000 and 2000, respectively) PEI were equally effective. Stabilising effect was also observed for other proteins including alcohol dehydrogenase, β-galactosidase and trypsin. Circular dichroism scan in the far UV range confirmed the protection offered by PEI against complete loss of protein secondary structure during storage. Studies with LDH revealed that the presence of polymer did not increase its denaturation temperature, but on the other hand, hindered the oxidation of free sulfhydryl groups catalysed by metal ions and resultant inactivation of the enzyme. Protection by the polymer was also seen during drying of LDH but not during freeze-thawing.