Number Of Polyelectrolyte Layers Research Articles

Study on Preparation and Performance of Acid pH-Responsive Intelligent Self-Healing Coating.

In this paper, microcapsules with acidic pH stimulus responsiveness were prepared through a one-step in situ polymerization method and a layer-by-layer assembly method. The effects of factors such as chitosan (CS) concentration, polymerization time, polymerization process temperature, and the number of polymerization layers on the performance of microcapsules were explored, and microcapsules with optimal performance were prepared and added to the epoxy coating. The morphology and structure of the microcapsules were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and zeta potential testing. The thermal stability and sustained release properties of the microcapsules were studied through thermogravimetric analysis and sustained release curve testing. Through scratch experiments, immersion experiments, salt spray experiments, and electrochemical impedance spectroscopy tests, the impact of the added amount of microcapsules on the self-healing performance and anti-corrosion performance of the coating in complex environments was explored. The results show that the optimal preparation process of acidic pH-responsive microcapsules requires that the concentration of chitosan is 2 mg/mL, the polymerization time of the polyelectrolyte layer is 8 h, the heating temperature during the polymerization process is 75 °C, and the number of polyelectrolyte layers is three. The prepared acidic pH-responsive microcapsules have good morphology, pH sensitivity, and thermal stability. The average particle size is approximately 203 μm, the drug loading rate reaches 59.74%, and the encapsulation rate reaches 63.99%. The optimal added amount of the acidic pH-responsive microcapsule coating is 15 wt%. The coating has a dual-trigger mechanism underlying it stimulus response capability and has an obvious stimulus response to acidic pH. It can inhibit corrosion in non-scratch areas, and its anti-corrosion ability is significantly stronger than that of epoxy coatings and ordinary self-healing coatings. The coating has a stronger repair effect and anti-corrosion ability when the environmental pH becomes acidic.

Investigating cationic and zwitterionic successive multiple ionic-polymer layer coatings for protein separation by capillary electrophoresis

Successive multiple ionic-polymer layers (SMILs) have long since proved their worth in capillary electrophoresis as they ensure stable electroosmotic flow (EOF) and relatively high separation efficiency. Recently, we demonstrated that plotting the plate height (H) against the solute migration velocity (u) enabled a reliable quantitative evaluation of the coating performances in terms of separation efficiency. In this work, various physicochemical and chemical parameters of the SMIL coating were studied and optimized in order to decrease the slope of the ascending part of the H vs u curve, which is known to be controlled by the homogeneity in charge of the coating surface and by the possible residual solute adsorption onto the coating surface. SMILs based on poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium styrene sulfonate) (PSS) were formed and the effect of each polyelectrolyte molar mass and of the number of polyelectrolyte layers (up to 21 layers) was studied. The use of polyethylene imine as an anchoring first layer was considered. More polyelectrolyte couples based on PDADMAC, polybrene, PSS, poly(vinyl sulfate), and poly(acrylic acid) were tested. Finally, zwitterionic polymers based on the poly(α-l-lysine) scaffold were synthesized and used as the last layer of SMILs, illustrating their ability to finetune the EOF, while maintaining good separation efficiency.

Uricase Crowding via Polyelectrolyte Layers Coacervation for Carbon Fiber-Based Electrochemical Detection of Uric Acid.

Urate oxidase (UOx) surrounded by synthetic macromolecules, such as polyethyleneimine (PEI), poly(allylamine hydrochloride) (PAH), and poly(sodium 4-styrenesulfonate) (PSS) is a convenient model of redox-active biomacromolecules in a crowded environment and could display high enzymatic activity towards uric acid, an important marker of COVID-19 patients. In this work, the carbon fiber electrode was modified with Prussian blue (PB) redox mediator, UOx layer, and a layer-by-layer assembled polyelectrolyte film, which forms a complex coacervate consisting of a weakly charged polyelectrolyte (PEI or PAH) and a highly charged one (PSS). The film deposition process was controlled by cyclic voltammetry and scanning electron microscopy coupled with energy-dispersive X-ray analysis (at the stage of PB deposition) and through quartz crystal microbalance technique (at latter stages) revealed uniform distribution of the polyelectrolyte layers. Variation of the polyelectrolyte film composition derived the following statements. (1) There is a linear correlation between electrochemical signal and concentration of uric acid in the range of 10-4-10-6 M. (2) An increase in the number of polyelectrolyte layers provides more reproducible values for uric acid concentration in real urine samples of SARS-CoV-2 patients measured by electrochemical enzyme assay, which are comparable to those of spectrophotometric assay. (3) The PAH/UOx/PSS/(PAH/PSS)2-coated carbon fiber electrode displays the highest sensitivity towards uric acid. (4) There is a high enzyme activity of UOx immobilized into the hydrogel nanolayer (values of the Michaelis-Menten constant are up to 2 μM) and, consequently, high affinity to uric acid.

Polarity studies of single polyelectrolyte layers in polyelectrolyte multilayers probed by steady state and life time doxorubicin fluorescence

HypothesisPolarity in polyelectrolyte multilayers (PEMs) may vary from the inner to the top layers of the film as the charge compensation of the layers is more effective inside the PEMs than in outer layers. Doxorubicin hydrochloride (DX) is used here to sense polarity at the single polyelectrolyte level inside PEMS. ExperimentalDX is complexed electrostatically to a polyanion, either polystyrene sulfonate (PSS) or polyacrylic acid (PAA) and assembled at selected positions in a multilayer of the polyanion and polyallylamine hydrochloride (PAH) as polycation. Local polarity in the layer domain is evaluated through changes in the intensity ratio of the first to second band of spectra of DX (I1/I2 ratio) by steady state fluorescence, and by Lifetime fluorescence. FindingsPAH/PSS multilayers, show a polarity similar to water with DX/PSS as top layer, decreasing to I1/I2 ratios similar to organic solvents as the number of polyelectrolyte layers assembled on top increases. For PAH/PAA multilayers, polarity values reflect a more polar environment than water when DX/PAA is the top layer, remaining unaltered by the assembly of polyelectrolyte layers on top. Results show that different polar environments may be present in a PEM when considering polarity at the single layer level.

Controlling the growth of Escherichia coli by layer-by-layer encapsulation

Escherichia coli is one of the most common commensal aerobic bacteria in the gut microbiota of humans (and other mammals). Nevertheless, if left free to proliferate, it can induce a large range of diseases from diarrhoea to extra-intestinal diseases. In recent years, this bacterium had become increasingly resistant to antibiotics. It is therefore essential to implement new approaches able to maintain both bacterial viability and to control their proliferation. In this context, we developed a process to encapsulate Escherichia coli in polymer shells. We took advantage of the fact that this bacterium has a negatively charged surface and modified it via a layer-by-layer process, i.e. with oppositely charged polyelectrolyte pairs (namely chitosan as the polycation and alginate or dextran sulfate as polyanion). We successfully demonstrate the controlled coating of the bacterial surface via zeta potential measurement, the viability of the encapsulated bacteria and a delay in growth due to the multilayer coating. This delay was dependent on the number of polyelectrolyte layers.

Coarse-Grained Molecular Dynamics (CG-MD) Simulation of the Encapsulation of Dexamethasone in PSS/PDDA Layer-by-Layer Assembled Polyelectrolyte Nanocapsules.

Experimental studies have reported the fundamental and applied science aspects of polyelectrolyte (PE) layer-by-layer (LbL) self-assembly. LbL nanocoating is a simple and robust technique that can be used to modify the surface properties of nearly any material. These modifications take place by adsorption of mere nanometers of PE to impart previously absent properties to the nanocoated substrate. Paper manufacturing, drug delivery, and antimicrobial applications have since been developed. LbL self-assembly has become a very lucrative field of research. Computational modeling of LbL nanocoating has received limited attention. PE simulations often require significant computational resources and make computational modeling studies challenging. In this study, atomic-level PE and dexamethasone models are developed and then converted into coarse-grained (CG) models. This modeling study is based on experimental results that were previously reported. The CG models showed the effect of salt concentration and the number of PE layers on the LbL drug nanocapsule. The suitability of the model was evaluated and showed that this model can serve as a predictive tool for an LbL-nanocoated drug delivery system. It is suggested that this model can be used to simulate LbL drug delivery systems before the experimental evaluation of the real systems take place.

Can Composite Janus Membranes with an Ultrathin Dense Hydrophilic Layer Resist Wetting in Membrane Distillation?

Tackling membrane wetting is an ongoing challenge for large-scale applications of membrane distillation (MD). Herein, composite Janus MD membranes comprising an ultrathin dense hydrophilic layer are developed by layer-by-layer assembling cationic polyethyleneimine and anionic poly(sodium 4-styrenesulfonate) polyelectrolytes on a hydrophobic polyvinylidene fluoride substrate. Using surfactant-containing saline water as the feed with low surface tension, experiments reveal that the number of polyelectrolyte layers, rather than surface wettability or surface charge, determines the anti-wetting performance of the composite Janus membranes. More deposited layers yield higher wetting resistance. With the aid of positron annihilation spectroscopy, this study, for the first time, demonstrates the origin of the excellent wetting resistance of the composite Janus membranes. The effective pore size of the polyelectrolyte multilayer decreases with an increase in the number of the deposited layer. The membrane with an ultrathin hydrophilic multilayer of 48 nm has a sufficiently small pore size to sieve out surfactant molecules from the feed solution via a size exclusion mechanism, thus protecting the hydrophobic substrate from being wetted by the low-surface-tension feed water. This study may pave the way for developing next-generation anti-wetting Janus membranes for robust membrane distillation.

Colloidal stability of silver nanoparticles with layer-by-layer shell of chitosan copolymers

The influence of polymeric shell formed by the layer-by-layer (LbL) assembly technique using chitosan or its grafted copolymers with dextran or poly(ethylene glycol) and dextran sulfate on physico-chemical properties and aggregation kinetics of silver nanoparticles (AgNP) was investigated. It is shown that the hydrodynamic diameter of encapsulated AgNP increases linearly with increasing the number of polyelectrolyte layers without sufficient aggregation. The critical concentrations of coagulation (CCC) and Hamaker constants (H) were determined in dependence on electrolyte charge, structure of polycation, and number of bilayers in the shells. While a shell consists of more than two bilayers, the values of critical electrolyte concentration and energy of interparticle interactions H are influenced mainly by copolymer structure. In all cases, the CCC value is more than doubled after formation of two or more bilayers over silver nanoparticle surface. The shells based on chitosan-poly(ethylene glycol) graft copolymer were proven to be the most effective in increasing aggregation stability in NaCl solutions, while chitosan-dextran graft copolymer effectively decreases van der Waals interaction between nanoparticles. Application of grafted copolymers allows one to obtain encapsulated colloids that are stable over a wide range of NaCl concentrations including the isotonic one and improve biocompatibility and targetability of nanovehicles engineered for therapeutic or imaging purposes.

Thickness of Polyelectrolyte Layers of Separately Confined Bacteria Alters Key Physiological Parameters on a Single Cell Level.

Confinement of bacterial cells in a matrix or in capsules is an integral part of many biotechnological applications. Here, the well-known layer-by-layer method of deposition of a polyelectrolyte film a few nanometers in thickness to confine separated bacterial cells in permeable and physically durable shells has been examined. Due to the physical properties of such a confinement, we found that this method enables investigation of effects of physical barriers against mass gain and cell division. Using the method of time-lapse confocal microscopy, we observed a prolonged lag phase, dependent on the number of polyelectrolyte layers. In the confinement, both the GFP fluorescent signal from the leaking T7 promoter and the cell size were increased by factors of more than five and two, respectively. This creates a paradigm shift that enables use of mechanical entrapment for control of bacterial cell physiology and opens possibilities of controlling the division rate as well as gene expression. These effects can be attributed to the perturbation of the sensing of the cell size, which results in disproportional synthesis of a cell envelope impinging the intracellular material and compels cells to grow rapidly. In addition, the charged surface of cells enables prolonged intercellular physical interaction and results in spherically shaped microcolonies.

SPR sensor based on polyelectrolyte complexes with DNA inclusion

Polyelectrolyte complexes offer unique possibilities for assembling nanostructures with recognition properties that find increasing application in various sensors for detection of biochemical interactions. In this work, the assembling of multilayers consisted of synthetic polyelectrolytes and DNA was monitored by changes in the SPR angle shift recorded after addition of each layer. For the first time, it was shown that primary modification of the Au surface influences the rate of the multilayer assembling and the shape of appropriate dependence of the SPR signal on the number of polyelectrolyte layers. Changes in the SPR signal were referred to the difference in rigidity of the layers and variation of the roughness of the surface reached by combination of the polyelectrolytes with different flexibility of the main chain and different distribution of the charges along the chain. The polyelectrolytes assembled make it possible to detect the DNA source and specific DNA interactions including its thermal and oxidative denaturation and intercalation with doxorubicin. The incubation of the SPR sensor in the doxorubicin solution made it possible to estimated the drug concentration in the range from 1∙10−12 to 1∙10-7 M (limit of detection 7∙10-13 M). Besides, the SPR sensor can be used for estimation of protective effect of antioxidants as was shown on the example of ascorbic acid suppressing DNA oxidation with reactive oxygen species.

Polyelectrolyte nanocontainers: Controlled binding and release of indomethacin

Herein, polyelectrolyte capsules containing anti-inflammatory drug indomethacin were formed using layer-by-layer strategy, which involves alternative deposition of oppositely charged polyelectrolytes, such as poly(acrylic acid) and poly(ethyleneimine) (or chitosan) onto the drug substrate. Two variants of encapsulation have been implemented: direct deposition of polyelectrolytes onto indomethacin dispersed in water at рН 6, and preliminary formation of soft matrix by solubilization of indomethacin in micellar solutions of cationic surfactants. The inclusion of indomethacin into nanosized polyelectrolyte capsules (hydrodynamic diameter of three- and five- layered capsules is 90–180 nm) has given a new form of indomethacin with the drug content of 0.20–0.25%, which exceeds its limiting solubility in water nearly by the factor of 40. The choice of materials and procedures used for preparation of capsules, as well as the number of polyelectrolyte layers that form shell has provided the control of the drug release from capsule and resulted in the design of pharmaceutical dosage forms with long-lasting effect.

Fluorescence enhancement of carbon dots by graphene for highly sensitive detection of tetracycline hydrochloride.

In this study, fluorescence of self-assembled multilayers (SAMs) of carbon dots (CDs) was found to be enhanced by graphene. The number of polyelectrolyte layers can be tuned to control the distance between CDs and graphene in SAMs. The enhanced fluorescence efficiency was found to be dependent on graphene concentration, degree of graphene reduction, and the distance between CDs and graphene surface. When graphene concentration and polyelectrolyte bilayer number were set to 0.005 mg mL−1 and 3 layers, respectively, fluorescence intensity of CDs could be increased up to 3.2 times. Tetracycline hydrochloride (Tc) could be detected by the established SAMs in the presence of graphene as the sensitivity was 2 orders higher than that of SAMs in the absence of graphene. Limit of detection of this sensing system was 0.9284 nM, which is 1–3 orders of magnitude lower than those of most of reported fluorescence sensors. This method could be successfully applied to detect trace Tc in milk samples.

Fabrication and Characterization of Chitosan/Alginate Multilayer Composite Membrane Supported by a Porous Poly (Acrylonitrile) Substrate for Pervaporation Dehydration of Alcohol

Chitosan (CS) and alginate (Alg) are complementary in their membrane performance, but the combination of them is normally difcult to use due to their different solubilities. Layer-by-Layer deposition appears to be an effective method for improving the separation efciency of a composite membrane. In this work, the polyelectrolyte multilayer composite membranes (PEMCMs) were fabricated by depositing CS and Alg solutions alternatively onto a hydrolyzed porous poly(acrylonitrile) (PAN) substrate under a reduced pressure, as evidenced by Attenuated total reflectance Fourier transform infrared spectroscopy, contact angle and zeta potential measurement. Pervaporation results showed that the water selectivity increased while the flux decreased with the growth of CS/Alg-based polyelectrolyte layer. It was interesting that the sorption process dominated the pervaporation process when the numbers of polyelectrolyte layers were less than 7. However, the diffusion effect was more profound than the sorption effect as more than 8 polyelectrolyte layers were deposited on the PAN substrate. In particular, the prepared CS/Alg PEMCMs exhibited highly improved water selectivities towards alcohol/water mixtures, and a good compromise between flux and separation factor was observed when compared to other polyelectrolyte-based membranes. For separating 90% IPA/water mixtures at 60 oC, the (CS/Alg)4 composite membrane displayed a separation factor of 4491 and a flux of 596 g/m2.h, respectively. These results indicate that the fabricated CS/Alg composite membranes are excellent waterpermselective ones for alcohol dehydration.

Improved bioavailability and pharmacokinetics of tea polyphenols by encapsulation into gelatin nanoparticles.

The authors prepared surface modified (with polyelectrolyte layers), tea polyphenols (TPP) encapsulated, gelatin nanoparticles (TPP-GNP) and characterised them. The size of the spherical nanoparticles was ∼50 nm. Number of polyelectrolyte layers and incubation time influenced the encapsulation efficiency (EE); highest EE was noted in nanoparticles with six polyelectrolyte layers (TPP-GNP-6L) incubated for 4 h. TPP released from TPP-GNP-6L in simulated biological fluids indicated protection and controlled release of TPP due to encapsulation. Mathematical modelling indicated anomalous type as a predominant mode of TPP release. TPP-GNP-6L exhibited enhanced pharmacokinetics in rabbit model compared with free TPP. The area under the concentration-time curve and mean residence time were significantly higher in TPP-GNP-6L compared with free TPP which provide an evidence of higher bioavailability of TPP due to encapsulation. The authors demonstrated that encapsulation of TPP into GNPs favoured slow and sustained release of TPP with improved pharmacokinetics and bioavailability thereby can prolong the action of TPP.

Hydrothermal carbonaceous sphere based stationary phase for anion exchange chromatography

Monodisperse carbonaceous spheres produced by the hydrothermal carbonization of sucrose were first applied as green stationary phase for ion chromatography after quaternization. Depending on the polycondensation of methylamine and 1,4-butanediol diglycidyl ether, polymer containing quaternary ammonium groups were facilely grafted onto the surfaces of hydrothermal carbonaceous spheres (HCSs). The quaternized HCSs with different number of polyelectrolyte layers were characterized by scanning electron microscopy, brunauer-emmett-teller, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and elemental analysis. The measurements of breakthrough curves demonstrated that more layers of grafted polyelectrolyte resulted in higher anion exchange capacity of stationary phase. With good stability, common inorganic anions, monocarboxylic acids, polarizable anions and carbohydrates were effectively separated on the stationary phases, respectively. The high hydrophilicity of HCS surface afforded excellent peak symmetry for all analytes. Furthermore, high-capacity HCSs stationary phase was successfully applied to detect fluoride in tea samples.

Grazing-incidence small-angle X-ray scattering property of double-layered gold nanoparticle arrays

Gold nanoparticle arrays fabricated via layer-by-layer technique were investigated using grazing-incidence small-angle X-ray scattering (GISAXS) method. Samples containing two gold nanoparticle layers that were separated by 5, 11, 15 and 21 polyelectrolyte (PE) interlayers were studied. By using different X-ray incident angles, correlations of gold nanoparticles (GNPs) in the same layer and in two different layers were investigated. It is found that both sideway correlations between GNPs in the same layer and vertical correlation between two gold nanoparticle layers depend on the thickness of PE interlayers. According to sideway correlation, the size of GNPs is determined to be (13.0 ± 0.5) nm in all of the four samples, which was also proved by scanning electron microscopy (SEM) and theoretical calculation of form factor of spherical particles. From vertical correlation, distance between two gold nanoparticle layers was determined for sample with 11, 15 and 21 PE layers. These distances can be reasonably explained with the number of PE layers and the thickness of single PE layer. These results indicate that by repeated depositing of oppositely charged PE layers, a true three-dimensional (3D) nanostructure can eventually be designed.

Polyelectrolyte micro- and nanoparticles with doxorubicin

Doxorubicin-containing micro- and nanoparticles obtained by layer-by-layer adsorption of dextran sulfate and chitosan on an insoluble antibiotic–polyanion complex with subsequent sonication were studied. The effects of the molecular mass of biopolymers, the number of polyelectrolyte layers, and the pH of the reaction medium on the composition, physicochemical properties, and the efficiency of doxorubicin incorporation have been examined. The release of doxorubicin and the mucoadhesive properties of the polyelectrolyte particles have been analyzed to determine the possibilities of their potential applications.

Fabrication of polyelectrolyte multilayered nano-capsules using a continuous layer-by-layer approach

The layer-by-layer approach is a highly versatile method for the fabrication of multilayered polymeric films and capsules. It has been widely investigated in research for various polyelectrolyte pairs and core template particles. However, the fabrication of nano-sized capsules at the larger scale is difficult and time consuming, due to the necessity of washing and centrifugation steps before the deposition of each polyelectrolyte layer. This results not only in a very long fabrication time, but also in the partial loss of particles during those intermediate steps. In this study, we introduced a continuous approach for the fabrication of multilayer polyelectrolyte based nano-capsules using calcium phosphate core nanoparticles and a tubular flow type reactor with the potential for synthesizing tens of milligrams of capsules per hour. Adsorption of the polyelectrolyte layer occurred in the tubing where particles and polyelectrolyte solution of choice were mixed, creating a layer of polyelectrolyte on the particles. After this, these newly surfaced-modified particles passed into the next segment of tubing, where they were mixed with a second polyelectrolyte of opposite charge. This process can be continuously repeated until the desired number of layers is achieved. One potential problem with this method concerned the presence of any excess polyelectrolyte in the tubing, so careful control of the amount of polymer added was crucial. It was found that slightly under dosing the amount of added polyelectrolyte ensured that negligible unadsorbed polyelectrolyte remained in solution. The particles created at each deposition step were stable, as they all had a zeta potential of greater than ±25mV. Furthermore the zeta potential measurements showed that charge reversal occurred at each stage. Having achieved the necessary number of polyelectrolyte layers, the calcium phosphate cores were easily removed via dissolution in either hydrochloric or acetic acid.

Inclusion of proteins into polyelectrolyte microcapsules by coprecipitation and adsorption

In present study microcapsules composed of synthetic (PSS and PAA) and biodegradable (DS and PAr) polyelectrolytes on calcium carbonate microparticles were obtained. The ultrastructural organization of biodegradable microcapsules was studied using transmission electron microscopy. The envelope of such capsules consisting of six polyelectrolyte layers is already well-formed, having the average thickness of 44 ± 3.0 nm, and their internal polyelectrolyte matrix is sparser compared to the synthetic microcapsules. Spectroscopy was employed to evaluate the efficiency of incorporation of FITC-labeled BSA into synthetic microcapsules by adsorption, depending on the number of polyelectrolyte layers. It was shown that the maximal amount of protein incorporated into the capsules with 6 or 7 polyelectrolyte layers (4 and 2 pg/capsule, correspondingly). As a result we conclude that, in comparison with co-precipitation, the use of adsorption allows to completely avoid the loss of protein upon encapsulation.

Liposomes as Drug Deposits in Multilayered Polymer Films

The ex vivo growth of implantable hepatic or cardiac tissue remains a challenge and novel approaches are highly sought after. We report an approach to use liposomes embedded within multilayered films as drug deposits to deliver active cargo to adherent cells. We verify and characterize the assembly of poly(l-lysine) (PLL)/alginate, PLL/poly(l-glutamic acid), PLL/poly(methacrylic acid) (PMA), and PLL/cholesterol-modified PMA (PMAc) films, and assess the myoblast and hepatocyte adhesion to these coatings using different numbers of polyelectrolyte layers. The assembly of liposome-containing multilayered coatings is monitored by QCM-D, and the films are visualized using microscopy. The myoblast and hepatocyte adhesion to these films using PLL/PMAc or poly(styrenesulfonate) (PSS)/poly(allyl amine hydrochloride) (PAH) as capping layers is evaluated. Finally, the uptake of fluorescent lipids from the surface by these cells is demonstrated and compared. The activity of this liposome-containing coating is confirmed for both cell lines by trapping the small cytotoxic compound thiocoraline within the liposomes. It is shown that the biological response depends on the number of capping layers, and is different for the two cell lines when the compound is delivered from the surface, while it is similar when administered from solution. Taken together, we demonstrate the potential of liposomes as drug deposits in multilayered films for surface-mediated drug delivery.