Deposition Of Polyethylenimine Research Articles

High-Performance Crown Ether-Modified Membranes for Selective Lithium Recovery from High Na+ and Mg2+ Brines Using Electrodialysis

The challenge of efficiently extracting Li+ from brines with high Na+ or Mg2+ concentrations has led to extensive research on developing highly selective separation membranes for electrodialysis. Various studies have demonstrated that nanofiltration membranes or adsorbents modified with crown ethers (CEs) such as 2-OH-12-crown-4-ether (12CE), 2-OH-18-crown-6-ether (18CE), and 2-OH-15-crown-5-ether (15CE) show selectivity for Li+ in brines. This study aims to develop high-performance cation exchange membranes (CEMs) using CEs to enhance Li+ selectivity and to compare the performance of various CE-modified membranes for selective electrodialysis. The novel CEM (CR671) was modified with 12CE, 18CE, and 15CE to identify the optimal CE for efficient Li+ recovery during brine electrodialysis. The modification process included polydopamine (PDA) treatment and the deposition of polyethyleneimine (PEI) complexes with the different CEs via hydrogen bonding. Interfacial polymerization with 1,3,5-benzenetricarbonyl trichloride-crosslinked PEI was used to create specific channels for Li+ transport within the modified membranes (12CE/CR671, 15CE/CR671, and 18CE/CR671). The successful application of CE coatings and Li+ selectivity of the modified membranes were verified through Fourier-transform infrared spectroscopy, zeta-potential measurements, and electrochemical impedance spectroscopy. Bench-scale electrodialysis tests showed significant improvements in permselectivity and Li+ flux for all three modified membranes. In brines with high Na+ and Mg2+ concentrations, the 15CE/CR671 membrane demonstrated more significant improvements in permselectivity compared to the 12CE/CR671 (3.3-fold and 1.7-fold) and the 18CE/CR671 (2.4-fold and 2.6-fold) membranes at current densities of 2.3 mA/cm2 and 2.2 mA/cm2, respectively. At higher current densities of 14.7 mA/cm2 in Mg2+-rich brine and 15.9 mA/cm2 in Na+-rich brine, the 15CE/CR671 membrane showed greater improvements in Li+ flux, approximately 2.1-fold and 2.3-fold, and 3.2-fold and 3.4-fold compared to the 12CE/CR671 and 18CE/CR671 membranes. This study underscores the superior performance of 15CE-modified membranes for efficient Li+ recovery with low energy demand and offers valuable insights for advancing electrodialysis processes in challenging brine environments.

Fabrication of nanofiltration membranes through the deposition of polyethyleneimine on SMA-polyethersulfone supports under acid catalysis for cationic dye/salt separation

Organic selective nanofiltration membranes, with high organic rejections and salt passages, have attracted extensive research attention, especially for dye/salt separations. In the present work, nanofiltration membranes with lower MWCO were prepared by depositing PEI aqueous on porous supports containing poly (styrene-maleic anhydride) (SMA), under the catalysis of sulfuric acid. The amines in PEI reacted with the anhydrides in SMA through electrophilic protonation–addition, forming a crosslinked dense layer. Under the optimal conditions, a nanofiltration membrane with a permeance of about 24.3 Lm−2h−1bar−1 and a MWCO of about 400 Da was obtained. The membrane was further evaluated by filtrating aqueous solutions of dye and/or salt. The rejections of cationic dyes (crystal violet and methylene blue) were as high as 99.9%. The rejection of Na2SO4 was only 3.6%. During the 24 h filtration process of the crystal violet and Na2SO4 mixed aqueous solution, the separation performance remained stable, indicating the PEI/SMA-PES nanofiltration membrane had excellent organic-water selectivity and organics-salts selectivity. The membrane may have good potential in positively charged dye desalination.

Fabrication of NiFe2O4@PEI and NiFe2O4@PPy nanospheres for adsorptive and photocatalytic removal of organic dyes

Spinel ferrites (MFe2O4) and their binary composites with polymers are frequently used to remove and degrade organic dyes due to their magnetic, optical, and biocompatible features. In this study, NiFe2O4, as a superparamagnetic core, was coated using the deposition of polyethylenimine (PEI) and in-situ oxidative polymerization of pyrrole (py). Fourier-transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were employed to analyze NiFe2O4, NiFe2O4@PEI, and NiFe2O4@PPy nanospheres. The morphology and chemical composition of nanoparticles were investigated using field emission scanning electron microscopy (FESEM). The formation of core-shell nanostructure was confirmed using transmission electron microscopy (TEM). A vibrating sample magnetometer (VSM) recorded the magnetic behavior of samples before and after coating polymers. NiFe2O4 superparamagnetic core exhibited high saturation magnetization (Ms) (63.6 emu/g) and easy collection by applying an external magnetic field. The maximum magnetic adsorption efficiencies were determined to be 92% and 72% for NiFe2O4@PEI (NiFe2O4/PEI weight ratio of 1:10) and NiFe2O4@PPy (NiFe2O4/PPy weight ratio of 1:50), respectively. Moreover, optical properties and photocatalytic activity were examined using UV-Vis spectroscopy. The band gap energy value was reduced from 2.3 eV for pure NiFe2O4 to 2.0 eV and 1.9 eV for NiFe2O4@PEI and NiFe2O4@PPy nanoparticles, respectively. The photocatalytic decomposition of methyl orange (MO) under visible illumination was improved after coating NiFe2O4 with PEI and PPy polymers. The results denote that NiFe2O4@PEI and NiFe2O4@PPy core-shell nanostructures are effective candidates for the adsorptive and photocatalytic removal of organic dyes from wastewater.

Activated carbon modified with polyethyleneimine and MgO: Better adsorption of aldehyde and production of regenerative VOC adsorbent using a photocatalyst

In this study, a renewable adsorbent containing a photocatalyst is developed that exhibits effective adsorption performance for polar volatile organic compounds (VOCs) that are not well adsorbed by activated carbon (AC). AC is used as the basic adsorbent, and the surface of the AC is modified with polyethyleneimine (PEI) and magnesium oxide (MgO) for the effective adsorption of polar VOCs. In addition, a renewable VOC adsorbent and filter are demonstrated by introducing titanium dioxide (TiO2) as a photocatalyst to impart regeneration. The changes in the physical and chemical structures of the AC surface due to the modification with PEI and the loading of MgO and its effects are confirmed through scanning electron microscopy, Brunauer–Emmett–Teller (BET) analysis, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy analyses. Developing slit pores containing polar functional groups on the AC through PEI deposition and loading MgO in the pore of AC increase the adsorption capacity of acetaldehyde by four times (3.08–13.8 mg g−1). In addition, PEI deposition shows high regeneration efficiency (86.4 %) with the application of TiO2. This study provides important insights into the development of renewable VOC filters that can be used for various VOCs.

Polyethylenimine Deposited on Phosphomolybdic-Acid-Loaded Polyacrylonitrile Membranes for Enhanced Dye/Salt Separation

Rationally designing membranes for efficient fractionation of dyes and salts is a great challenge in the membrane community. Here, a composite loose nanofiltration membrane (NF) was fabricated by depositing polyethylenimine (PEI) onto a phosphomolybdic acid (PMo12)-loaded polyacrylonitrile substrate followed by cross-linking with glutaraldehyde. The physical and chemical properties of the loose NF membrane were systematically investigated. Compared with the unloaded membrane, the introduction of PMo12 regulates the deposition of PEI, leading to a smaller pore size, higher hydrophilicity, and stronger charge of the loose NF membrane. The optimized loose NF membrane presented an extremely low rejection of <2.00% to inorganic salts sodium sulfate (Na2SO4), magnesium sulfate, magnesium chloride, and sodium chloride, while maintaining a high rejection of >99.00% to organic dye Congo red (CR). In addition, the loose NF membrane is capable of fractionating CR/Na2SO4 mixtures with an astonishing separation factor of 59.18. Moreover, the stability of the loose NF membrane is qualified for a 100 h period filtration. This work provides an efficient strategy to fabricate loose NF membranes with high separation performance for the fractionation of dyes or salts.

Superhydrophobic self-extinguishing cotton fabrics for electromagnetic interference shielding and human motion detection

• Multifunctional cotton fabric has been prepared via a layer-by-layer method. • Cotton-10BL-Si shows superhydrophobic and self-extinguishing behaviors. • Cotton-10BL-Si has great potential in EMI shielding and motion sensors. • Cotton-10BL-Si shows satisfying washability and durability. Multifunctional intelligent fire-safe cotton fabric promises next-generation fire-fighting uniform and sensor applications. However, cotton fabrics' hygroscopicity and intrinsic flammability significantly impede their potential applications in industries. Herein, we report a superhydrophobic fireproof cotton fabric (PEI-APP-PEI-MXene) generated via sequential layer-by-layer deposition of polyethyleneimine (PEI), ammonium polyphosphate (APP), and titanium carbide (MXene), followed by hydrophobic treatment with silicone elastomer. Compared to untreated cotton, the treated cotton fabric with 10 polymolecular layers exhibits ∼43% and ∼42% reductions in the peak heat release rate and total heat release, respectively, a desired UL-94 V-0 rating, and a high limiting oxygen index (LOI) value of 39.5 vol.%. In addition to that, the treated fabrics displayed improved electromagnetic interference (EMI) shielding and motion-sensing abilities. The presented work provides a facile and effective surface modification approach to generate multifunctional cotton fabrics with promising practical applications.

Electron Transport Layer-Free Ruddlesden–Popper Two-Dimensional Perovskite Solar Cells Enabled by Tuning the Work Function of Fluorine-Doped Tin Oxide Electrodes

Organic–inorganic halide two-dimensional (2D) layered perovskites have been demonstrated to have better environmental stability than conventional three-dimensional perovskites. In this study, we investigate the fabrication of electron transport layer (ETL)-free Ruddlesden–Popper 2D perovskite solar cells (PSCs) by tuning the work function of a fluorine-doped tin oxide (FTO) electrode. With the deposition of polyethylenimine (PEIE) onto its surface, the work function of the FTO electrode could be raised from −4.72 to −4.08 eV, which is more suitable for electron extraction from the perovskite absorber. Using this technique, the ETL-free 2D PSCs exhibited an excellent power conversion efficiency (PCE) of 12.7% (on average), which is substantially higher than that of PSCs fabricated on a pristine FTO electrode (9.6%). Compared with the PSCs using TiO2, the ETL-free PSCs could be fabricated under a low processing temperature of 100 °C with excellent long-term stability. After 15 days, the FTO/PEIE-based ETL-free PSCs showed a PCE degradation of 16%, which is significantly lower than that of the TiO2-based case (29%). The best-performing PSC using a FTO/PEIE cathode showed a high PCE of 13.0%, with a small hysteresis degree of 2.3%.

Synthesis of poly(ethyleneimine)-functionalized mesoporous silica gel with dual loading of host ion and crosslinking for enhanced heavy metal removal in multinary solutions

Polyethyleneimine (PEI)-functionalized mesoporous silica gel (SG) was synthesized through dual loading (d-PEI-SG) of copper (Cu) as a host ion for Cu(II)-PEI complex and crosslinking with glutaraldehyde in the synthesis pathway to enhance deposition of PEI on the SG. For comparison, the PEI-functionalized SG was also prepared through single loading (s-PEI-SG) of the host ion and crosslinking with glutaraldehyde. In thermogravimetric analysis, the weight loss of d-PEI-SG at 110–500 °C (7.8%) was greater than that of s-PEI-SG (2.8%), indicating the enhanced deposition of PEI on the silica gel surface of d-PEI-SG. The elemental composition from X-ray photoelectron spectroscopy analysis demonstrated that relative quantities of carbon and nitrogen in d-PEI-SG were larger than those of s-PEI-SG. In batch tests, the maximum Cu(II) adsorption capacity of d-PEI-SG was determined to 170.4 μmol g−1, which was four times larger than that (41.8 μmol g−1) of s-PEI-SG. In a multinary solution of divalent metal ions (Cu(II), Pb(II), Zn(II), Ni(II), and Co(II)) and trivalent/tetravalent metal ions (Cu(II), Al(III), Cr(III), and Zr(IV)), d-PEI-SG had a higher Cu(II) adsorption capacity and selectivity than s-PEI-SG. Column experiments were also conducted in the multinary solution of Cu(II), Pb(II), Zn(II), Ni(II), and Co(II), demonstrating that d-PEI-SG could remove more Cu(II) than s-PEI-SG in flow-through conditions.

A platform for light-controlled formation of free-stranding lipid membranes

The engineering of artificial cells is one of the most significant scientific challenges. Thus, controlled fabrication and in situ monitoring of biomimetic nanoscale objects are among the central issues in current science and technology. Studies of transmembrane channels and cell mechanics often require the formation of lipid bilayers (LBs), their modification and their transfer to a particular place. We present here a novel approach for remotely controlled manipulation of LBs. Layer-by-layer deposition of polyethyleneimine and poly(sodium 4-styrenesulfonate) on a nanostructured TiO 2 photoanode was performed to obtain a surface with the desired net charge and to enhance photocatalytic performance. The LB was deposited on top of a multi-layer positive polymer cushion by the dispersion of negative vesicles. The separation distance between the electrostatically linked polyelectrolyte cushion and the LB can be adjusted by changing the environmental pH, as zwitter-ionic lipid molecules undergo pH-triggered charge-shifting. Protons were generated remotely by photoanodic water decomposition on the TiO 2 surface under 365 nm illumination. The resulting pH gradient was characterized by scanning vibrating electrode and scanning ion-selective electrode techniques. The light-induced reversible detachment of the LB from the polymer-cushioned photoactive substrate was found to correlate with suggested impedance models.

Layer‐by‐layer self‐assembly of multifunctional enzymatic UF membranes

ABSTRACTIn order to eliminate membrane fouling and to ensure enzymatic hydrolysis of urea, multifunctional biocatalytic membranes were prepared by using urease (URE) and trypsin (TRY) enzymes on the sulfonated polysulfone (SPSf) ultrafiltration membrane via layer‐by‐layer (LbL) self‐assembly method. The membrane architecture consisted of multilayer assembly with TRY and URE enzymes as the outer layer and inner sandwiched layer, respectively. Polyethyleneimine (PEI) and alginate (ALG) were used as cationic and anionic polyelectrolytes. Sulfonation and PEI deposition were successfully accomplished as confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy analysis, contact angle measurements, staining with toluidine blue and Congo red dyes and dead‐end filtration experiments. A characteristic value of SPSf membrane with a high water permeability (1000 L/m2.h.bar) and 95% bovine serum albumin (BSA) rejection was observed. In static conditions, URE activities of SPSf2‐PEI‐URE membrane were not affected by BSA fouling, while TRY immobilizations with increased concentrations (SPSf2‐PEI‐URE‐PEI‐ALG‐TRY) significantly lowered the activity of URE. In dynamic conditions, each deposited layer exhibited individual resistance to flow that can be considered as irreversible fouling and caused 90% of flux decline for the SPSf2‐PEI‐URE‐PEI‐ALG‐TRY membrane assembly. The recovery of the initial flux for the multilayered membrane at the end of six fouling and washing cycles was observed 85%. Moreover, at the end of 5 cycles, 78% of the URE initial activity of the multilayered membrane was preserved. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48750.

Purification of monoclonal antibodies in a stirred cell with polyethyleneimine‐modified polyethersulfone ultrafiltration membrane

AbstractBACKGROUNDCharged ultrafiltration membranes combined with optimal operating conditions can be used to enable monoclonal antibody purification. Positively charged ligands bound to the membrane surface can significantly contribute to the adsorption of negatively charged proteins and enhance the purification process.RESULTSIn this work, commercially available 500 kDa polyethersulfone ultrafiltration membranes were modified by sulfonation, followed by deposition of polyethyleneimine (PEI) and crosslinking with butanedioldiglycidylether. Polymer molecules of 2 and 10 kDa were used to evaluate how polymer size influences the fractionation of a harvested Chinese hamster ovary cell culture fluid containing a monoclonal antibody by ultrafiltration at different operational pH values. The precursor and modified membranes were analyzed by X‐ray photoelectron spectroscopy, which confirmed the successful modification of membranes. Nitrogen analysis showed the presence of amine groups, clearly confirming immobilization of PEI onto the membrane surface. When 10 kDa PEI is chosen for membrane modification, the intensity of this signal increases, as predicted for a higher‐molecular‐weight polymer. Ultrafiltration performance indicators (fluxes, transmissions, yields) were determined and compared for the modified and precursor membranes, with the PEI‐derived membranes showing ability for pH modulation of selectivity.CONCLUSIONHigh purities were consistently observed at pH 9 owing to a simultaneous decrease in the transmission of soluble protein and increase in both IgG transmission and adsorptive capacity of the membranes. A single‐step process at pH 9 renders a permeate with an antibody purity of 96%, using a non‐crosslinked membrane modified with 10 kDa PEI. © 2019 Society of Chemical Industry

A probeless and label-free electrochemical immunosensor for cystatin C detection based on ferrocene functionalized-graphene platform

A novel electrochemical sensor with inherent redox activity mediated by ferrocene for Cystatin C (CysC), an early kidney failure biomarker, is described. The current response was mediated by graphene oxide-ferrocene nanofilm with redox-activity coming from electroactive species surface-confined. Anti-CysC antibodies were immobilized by their Fc portions on the drop-casting polyethyleneimine (PEI) film for improving the sensitivity and reproducibility. Stepwise modifications of the nanostructured surface were characterized by electrochemical techniques, FT-IR and AFM. FT-IR confirmed the formation of the Fc-GO nanocomposite and PEI deposition on the electrode surface. The AFM micrographs confirmed a nanometric film of Fc-GO and PEI. The sensor platform showed a response from 0.1 to 1000 ng/mL and lower limit of detection (LOD) of 0.03 ng/mL of CysC, with good accuracy, specificity and it was successfully applied for CysC detection. Advantages of this immunosensor include rapid testing with minimal steps by the simple use of an intrinsic redox probe, working in a reduction potential, which avoids potential interferences. This proposal attempts to circumvent amperometric detection limitations and provides a promising candidate for future point-of-care diagnostics without redox probe additional solutions for measurements.

Electrochemical triggering of lipid bilayer lift-off oscillation at the electrode interface.

In situ studies of transmembrane channels often require a model bioinspired artificial lipid bilayer (LB) decoupled from its underlaying support. Obtaining free-standing lipid membranes is still a challenge. In this study, we suggest an electrochemical approach for LB separation from its solid support via hydroquinone oxidation. Layer-by-layer deposition of polyethylenimine (PEI) and polystyrene sulfonate (PSS) on the gold electrode was performed to obtain a polymeric nanocushion of [PEI/PSS]3/PEI. The LB was deposited on top of an underlaying polymer support from the dispersion of small unilamellar vesicles due to their electrostatic attraction to the polymer support. Since lipid zwitterions demonstrate pH-dependent charge shifting, the separation distance between the polyelectrolyte support and LB can be adjusted by changing the environmental pH, leading to lipid molecules recharge. The proton generation associated with hydroquinone oxidation was studied using scanning vibrating electrode and scanning ion-selective electrode techniques. Electrochemical impedance spectroscopy is suggested to be a powerful instrument for the in situ observation of processes associated with the LB-solid support interface. Electrochemical spectroscopy highlighted the reversible disappearance of the LB impact on impedance in acidic conditions set by dilute acid addition as well as by electrochemical proton release on the gold electrode due to hydroquinone oxidation.

Polyelectrolyte-coated ultra-small nanoparticles with Tb(III)-centered luminescence as cell labels with unusual charge effect on their cell internalization

The present work reports ultra-small polyelectrolyte-coated water insoluble Tb(III) complex species with bright Tb(III)-centered luminescence resulted from efficient ligand-to-metal energy transfer as efficient labels for Hep-2 cells. The flow cytometry data revealed the enhanced cellular uptake of negatively charged nanoparticles coated by the polystyrenesulfonate (PSS)-monolayer versus the positively charged nanoparticles. The latter are obtained by layer-by-layer deposition of polyethyleneimine (PEI) onto PSS-coated ones. Confocal and TEM images of Hep-2 cells exposed by the colloids confirm favorable cell internalization of the PSS- compared to PEI-PSS-coated colloids illustrating unusual charge-effect. Dynamic light scattering data indicate significant effect of the biological background exemplified by serum bovine albumin and phosphatidylcholine-based bilayers on the exterior charge and aggregation behavior of the colloids. The obtained results reveal the PSS-coated nanoparticles based on water insoluble Tb(III) complex as promising cell labels.

Modification of Nanofiber Support Layer for Thin Film Composite forward Osmosis Membranes via Layer-by-Layer Polyelectrolyte Deposition.

Electrospun nanofiber-supported thin film composite membranes are among the most promising membranes for seawater desalination via forward osmosis. In this study, a high-performance electrospun polyvinylidenefluoride (PVDF) nanofiber-supported thin film composite (TFC) membrane was successfully fabricated after molecular layer-by-layer polyelectrolyte deposition. Negatively-charged electrospun polyacrylic acid (PAA) nanofibers were deposited on electrospun PVDF nanofibers to form a support layer consisted of PVDF and PAA nanofibers. This resulted to a more hydrophilic support compared to the plain PVDF nanofiber support. The PVDF-PAA nanofiber support then underwent a layer-by-layer deposition of polyethylenimine (PEI) and PAA to form a polyelectrolyte layer on the nanofiber surface prior to interfacial polymerization, which forms the selective polyamide layer of TFC membranes. The resultant PVDF-LbL TFC membrane exhibited enhanced hydrophilicity and porosity, without sacrificing mechanical strength. As a result, it showed high pure water permeability and low structural parameter values of 4.12 L m−2 h−1 bar−1 and 221 µm, respectively, significantly better compared to commercial FO membrane. Layer-by-layer deposition of polyelectrolyte is therefore a useful and practical modification method for fabrication of high performance nanofiber-supported TFC membrane.

Layer-by-layer assembly of graphene on polyimide films via thermal imidization and synchronous reduction of graphene oxide

To investigate the effects of holding time after deposition of polyethylenimine (PEI) solution and molecular weight of PEI on the surface morphology of multi-layer films prepared by layer-by-layer (LbL) method, polyamic acid (PAA)/PEI/graphene oxide (GO) films were prepared using different holding times and different molecular weights of PEI. To convert PAA into polyimide (PI), the films were thermally imidized after film deposition. In this process, GO was also converted into partially reduced GO (rGO). The effects of holding time and molecular weight of PEI on the surface morphology and the sheet resistance of PI/PEI/rGO films were investigated. Also, to investigate the effect of rGO on the barrier properties of PI based multilayer films, (PI/PEI/rGO/PEI)6 films were prepared by LbL method. Longer holding time (10 min) and smaller molecular weight (25,000) of PEI lead to relatively flat surfaces, but shorter holding time (5 min) and larger molecular weight (75,000) result in wrinkled and overlapped surfaces. The sheet resistance of PI/PEI25K/rGO films prepared with holding time 10 and 5 min is 502.1 kΩ/sq and out of range (> 2000 kΩ/sq), respectively. The sheet resistance of PI/PEI75K/rGO films prepared with holding time 10 min is out of range (> 2000 kΩ/sq). Gas transmission rate (GTR) and permeability coefficient of (PI/PEI25K/rGO/PEI25K)6 are lower than those of (PI/PEI75K/rGO/PEI75K)6, respectively.

A flow-through enzymatic microreactor immobilizing lipase based on layer-by-layer method for biosynthetic process: Catalyzing the transesterification of soybean oil for fatty acid methyl ester production

Abstract A simple and convenient method was proposed in this paper to develop a flow-through enzymatic micro-reactor made from polytetrafluoroethylene (PTFE). It consisted of the polydopamine layer (functioned as a primer) and layer by layer (LBL) coatings composed of polyethylenimine (PEI) and lipase. The multiple deposition of PEI and lipase was the key factor of increasing the enzyme loading on microreactor. After 8 PEI/lipase layers, enzyme loading on the inner surface of 5-m microchannel reached a maximum (350 μg to 400 μg), compared with approximately 20 μg in single layer. Microreactor with higher enzyme loading was successfully applied on transesterification of soybean oil for effective fatty acid methyl ester (FAME, biodiesel) production. A 95.2% conversion rate of biodiesel can be achieved in 53 min under optimized conditions, instead of a couple of hours in the traditional batch reaction.

Polyelectrolyte nanocapsules with controlled properties fabricated by layer-by-layer deposition of polyethyleneimine and graft-copolyimide with polymethacrylic acid side chains

Herein, the polyelectrolyte capsules containing spectral and fluorescent probes were formed using the layer-by-layer method based on the layerwise deposition of oppositely charged polyelectrolytes on the micelles of different ionic surfactants, cetyltrimethylammonium bromide and sodium dodecyl sulfate, with previously solubilized substrates. The branched polyethyleneimine was used as a cationic polyelectrolyte, and the graft-copolymer with a polyimide backbone and polymethacrylic acid side chains acts as an anionic polyelectrolyte. The three-, five- and seven-layered capsules were synthesized. Dynamic light scattering method shows that irrespective of the nature of ionic surfactants the size of capsules ranges within 150–200nm, but in the case of sodium dodecyl sulfate an increase the number of deposited layers results in an increase in particle size, whereas the opposite trend is observed in the case of cetyltrimethylammonium bromide. A charge of the surfactant used has little effect on the protective properties of the obtained capsules, but allows of forming the particles with different size behaviors, which can be important for the formation of nanocapsules and their use in drug delivery.

Surface modification of polysulfone based hemodialysis membranes with layer by layer self assembly of polyethyleneimine/alginate-heparin: a simple polyelectrolyte blend approach for heparin immobilization

This study intends to improve blood compatibility of polysulfone (PSF) membranes by generating a nonthrombogenic surface through heparin immobilization. To achieve this task, the support membrane prepared from a blend of PSF and sulfonated polysulfone (SPSF) was modified with layer by layer (LBL) deposition of polyethyleneimine (PEI) and alginate (ALG) and heparin blended with ALG was immobilized only on the outermost surface of the LBL assembly. The results have shown that the adsorption of human plasma proteins and platelet activation on the LBL modified membranes decreased significantly compared with the unmodified PSF and PSF-SPSF blend membranes. Furthermore, blending ALG with a small amount of heparin remarkably prolonged the APTT values of heparin free PEI/ALG coated membranes. It is envisaged that the use of a blend of HEP and ALG only in the terminating layer of the LBL assembly can be an economical and alternative modification technique to create nonthrombogenic surfaces.

Reversible multi polyelectrolyte layers on gold nanoparticles

Gold nanoparticles surface can be easily modified by different molecules such as polyelectrolytes. In a typical multilayer system made of polyethyleneimine and poly(styrene sulfonate)sodium alternated layers around gold nanoparticles, we have evaluated the interactions between the different layers and the relative strength of interfacial properties. By means of UV–Visible and FTIR spectroscopies, we have shown that due to its amine functionalities, the bonding of polyethyleneimine to gold particles is stronger than the one implied with the sulfonate anion in the PSS inducing a clean removal of this latter after the last polyethyleneimine deposition. Considering that polyethyleneimine is cytotoxic and that only weak covalent bonds are concerned in polyelectrolyte multilayer, this last point is of main importance since external degradation thus exposing polyethyleneimine sub-layer of multilayer films to in vivo tissue cells can occur by many ways.