Polyelectrolyte Multilayer Films Research Articles

Highly sensitive and simple liquid chromatography assay with ion-pairing extraction and visible detection for quantification of gold from nanoparticles

A simple isocratic HPLC method using visible detection was developed and validated for the quantification of gold in nanoparticles (AuNP). After a first step of oxidation of nanoparticles, an ion-pair between tetrachloroaurate anion and the cationic dye Rhodamine B was formed and extracted from the aqueous media with the help of an organic solvent. The corresponding Rhodamine B was finally quantified by reversed phase liquid chromatography using a Nucleosil C18 (150mm × 4.6mm, 3µm) column and with a mobile phase containing acetonitrile and 0.1% trifluoroacetic acid aqueous solution (25/75, V/V) at 1.0mLmin−1.and at a wavelength of 555nm. The method was validated using methodology described by the International Conference on Harmonization and was shown to be specific, precise (RSD < 11%), accurate and linear in the range of 0.1 – 30.0µM with a lower limit of quantification (LLOQ) of 0.1µM. This method was in a first time applied to AuNP quality control after their synthesis. In a second time, the absence of gold leakage (either as AuNP or gold salt form) from nanostructured multilayered polyelectrolyte films under shear stress was assessed.

Synthetic Lift-off Polymer beneath Layer-by-Layer Films for Surface-Mediated Drug Delivery.

A broad range of biomaterials coatings and thin film drug delivery systems require a strategy for the immobilization, retention, and release of coatings from surfaces such as patches, inserts, and microneedles under physiological conditions. Here we report a polymer designed to provide a dynamic surface, one that first functions as a platform for electrostatic thin film assembly and releases the film once in an in vivo environment. Atom transfer radical polymerization (ATRP) was used to synthesize this polymer poly(o-nitrobenzyl-methacrylate-co-hydroxyethyl-methacrylate-co-poly(ethylene-glycol)-methacrylate) (PNHP), embedded beneath multilayered polyelectrolyte films. Such a base layer is designed to photochemically pattern negative charge onto a solid substrate, assist deposition of smooth layer-by-layer (LbL) polyelectrolyte in mildly acidic buffers and rapidly dissolve at physiological pH, thus lifting off the LbL films. To explore potential uses in the biomedical field, a lysozyme (Lys)/poly(acrylic acid) (PAA) multilayer film was developed on PNHP-coated silicon wafers to construct prototype antimicrobial shunts. Film thickness was shown to grow exponentially with increasing deposition cycles, and effective drug loading and in vitro release was confirmed by the dose-dependent inhibition of Escherichia coli (E. coli) growth. The efficacy of this approach is further demonstrated in LbL-coated microscale needle arrays ultimately of interest for vaccine applications. Using PNHP as a photoresist, LbL films were confined to the tips of the microneedles, which circumvented drug waste at the patch base. Subsequent confocal images confirmed rapid LbL film implantation of PNHP at microneedle penetration sites on mouse skin. Furthermore, in human skin biopsies, we achieved efficient immune activation demonstrated by a rapid uptake of vaccine adjuvant from microneedle-delivered PNHP LbL film in up to 37% of antigen-presenting cells (APC), providing an unprecedented LbL microneedle platform for human vaccination.

UV and NIR-Responsive Layer-by-Layer Films Containing 6-Bromo-7-hydroxycoumarin Photolabile Groups.

This paper describes polyelectrolyte multilayer films prepared by the layer-by-layer (LbL) technique capable of undergoing dissolution upon exposure to either ultraviolet or near-infrared light. Film dissolution is driven by photochemical deprotection of a random methacrylic copolymer with two types of side chains: (i) 6-bromo-7-hydroxycoumarinyl esters, photocleavable groups that are known to have substantial two-photon photolysis cross sections, and (ii) cationic residues from the commercially available monomer N,N-dimethylaminoethyl methacrylate (DMAEMA). In addition, the dependence of stability of both unirradiated and irradiated films on pH provides experimental evidence for the necessity of disrupting both ion-pairing and hydrophobic interactions between polyelectrolytes to realize film dissolution. This work therefore provides both new fundamental insight regarding photolabile LbL films and expands their applied capabilities to nonlinear photochemical processes.

* Calvarial Bone Regeneration Is Enhanced by Sequential Delivery of FGF-2 and BMP-2 from Layer-by-Layer Coatings with a Biomimetic Calcium Phosphate Barrier Layer.

A drug delivery coating for synthetic bone grafts has been developed to provide sequential delivery of multiple osteoinductive factors to better mimic aspects of the natural regenerative process. The coating is composed of a biomimetic calcium phosphate (bCaP) layer that is applied to a synthetic bone graft and then covered with a poly-l-Lysine/poly-l-Glutamic acid polyelectrolyte multilayer (PEM) film. Bone morphogenetic protein-2 (BMP-2) was applied before the coating process directly on the synthetic bone graft and then, bCaP-PEM was deposited followed by adsorption of fibroblast growth factor-2 (FGF-2) into the PEM layer. Cells access the FGF-2 immediately, while the bCaP-PEM temporally delays the cell access to BMP-2. In vitro studies with cells derived from mouse calvarial bones demonstrated that Sca-1 and CD-166 positive osteoblast progenitor cells proliferated in response to media dosing with FGF-2. Coated scaffolds with BMP-2 and FGF-2 were implanted in mouse calvarial bone defects and harvested at 1 and 3 weeks. After 1 week in vivo, proliferation of cells, including Sca-1+ progenitors, was observed with low dose FGF-2 and BMP-2 compared to BMP-2 alone, indicating that in vivo delivery of FGF-2 activated a similar population of cells as shown by in vitro testing. At 3 weeks, FGF-2 and BMP-2 delivery increased bone formation more than BMP-2 alone, particularly in the center of the defect, confirming that the proliferation of the Sca-1 positive osteoprogenitors by FGF-2 was associated with increased bone healing. Areas of bone mineralization were positive for double fluorochrome labeling of calcium and alkaline phosphatase staining of osteoblasts, along with increased TRAP+ osteoclasts, demonstrating active bone formation distinct from the bone-like collagen/hydroxyapatite scaffold. In conclusion, the addition of a bCaP layer to PEM delayed access to BMP-2 and allowed the FGF-2 stimulated progenitors to populate the scaffold before differentiating in response to BMP-2, leading to improved bone defect healing.

Polymeric ionic liquid based on magnetic materials fabricated through layer-by-layer assembly as adsorbents for extraction of pesticides

In this study, layer-by-layer assembly of polyelectrolyte multilayer films on magnetic silica provided a convenient and controllable way to prepare polymeric ionic liquid-based magnetic adsorbents. The resulting particles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic measurements. The data showed that the magnetic particles had more homogeneous spherical shapes with higher saturation magnetization when compared to those obtained by free radical polymerization method. This facilitated the convenient collection of magnetic particles, with higher extraction repeatability. The extraction performance of the multilayer polymeric ionic liquid-based adsorbents was evaluated by magnetic solid-phase extraction of four pesticides including quinalphos, fenthion, phoxim, and chlorpropham. The data suggested that the extraction efficiency depended on the number of layers in the film. The parameters affecting the extraction efficiency were optimized, and good linearity ranging from 2 to 250μgL−1 was obtained with correlation coefficients of 0.9994–0.9998. Moreover, the proposed method presented low limit of detection (0.5μgL−1, S/N=3) and limit of quantification (1.5μgL−1, S/N=10), and good repeatability expressed by the relative standard deviation (2.0%–4.6%, n=5). The extraction recoveries of four pesticides were found to range from 58.9% to 85.8%. The reliability of the proposed method was demonstrated by analyzing environmental water samples, and the results revealed satisfactory spiked recovery, relative standard deviation, and selectivity.

Effect of anionic surfactant on alginate‐chitosan polyelectrolyte multilayer thickness

ABSTRACTAlginate and chitosan are among the most common biopolyelectrolytes. Surfactants can be included in alginate and chitosan formulations in order to improve their physical and functional properties. In the present study, the effect of the anionic surfactant sodium dodecyl sulfate (SDS) on alginate‐chitosan polyelectrolyte multilayer (PEM) films is reported for the first time. Layer‐by‐layer deposition technique was employed to prepare the PEM samples and the samples were characterized by ellipsometry, X‐ray reflectivity, atomic force microscopy, and quartz crystal microbalance with dissipation. Incorporation of SDS into PEM formulations increased the film thickness and an increased adsorption behavior between alginate and chitosan layers are observed. Since the concentration of SDS was below its critical micelle concentration, no micelle formation was expected and hydrophobic‐hydrophobic interaction between alginate and SDS might be the main reason. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1798–1803

Polyelectrolyte multilayers for bio-applications: recent advancements.

The synergistic relationship between structure and the bulk properties of polyelectrolyte multilayer (PEM) films has generated tremendous interest in their application for loading and release of bioactive species. Layer-by-layer assembly is the simplest, cost effective process for fabrication of such PEMs films, leading to one of the most widely accepted platforms for incorporating biological molecules with nanometre precision. The bulk reservoir properties of PEM films render them a potential candidate for applications such as biosensing, drug delivery and tissue engineering. Various biomolecules such as proteins, DNA, RNA or other desired molecules can be incorporated into the PEM stack via electrostatic interactions and various other secondary interactions such as hydrophobic interactions. The location and availability of the biological molecules within the PEM stack mediates its applicability in various fields of biomedical engineering such as programmed drug delivery. The development of advanced technologies for biomedical applications using PEM films has seen rapid progress recently. This review briefly summarises the recent successes of PEM being utilised for diverse bio-applications.

Polyelectrolyte Multilayer Film Coated Silver Nanorods: An Effective Carrier System for Externally Activated Drug Delivery

Nanoparticle anisotropy offers unique functions and features in comparison with spherical nanoparticles (NPs) and makes anisotropic nanoparticles (ANPs) promising candidates in applications like drug delivery, imaging, biosensing and theranostics. Presence of surface active groups (e.g. amine, and carboxylate groups) on their surface provides binding sites for ligands or other biomolecules, and hence, this could be targeted for specific part or cells in our body. In the quest of such surface modification, functionalization of ANPs along Layer-by-Layer (LbL) coating of oppositely charged polyelectrolytes (PE) reduces cellular toxicity and promotes easy encapsulation of drugs. In this work, we report the silver nanorods (AgNRs) synthesis by adsorbate directed synthetic approach using cetyltrimethyl ammonium bromide (CTAB). The formed ANPs is investigated by scanning electron microscopy (SEM) and UV-Visible (UV-Vis) spectroscopy revealing the shaping of AgNRs of 3-16 nm aspect ratio with some presence of triangles. These NRs were further coated with bio polymers of chitosan (CH) and dextran sulphate (DS) through LbL approach and used for encapsulation of water soluble anti-bacterial drugs like ciprofloxacin hydrochloride (CFH). The encapsulation of drugs and profiles of drug release were investigated and compared to that of spherical silver nanoparticles (AgNPs). The added advantages of the proposed drug delivery system (DDS) can be externally activated to release the loaded drug and used as contrast agents for biological imaging under exposure to NIR light. Such system shows unique and attractive characteristics required for drug delivery and bioimaging thus offering the scope for further development as theranostic material.

Assembly, Morphology, Diffusivity, and Indentation of Hydrogel-Supported Lipid Bilayers.

Recognizing the limitations of solid-supported lipid bilayers to reproduce the behavior of cell membranes, including bendability, transmembrane protein inclusion, and virus entry, this study describes a novel biomimetic system for cell membranes with the potential to overcome these and other limitations. The developed strategy utilizes a hydrogel with tunable mechanical behavior that resembles those of living cells as the soft support for the phospholipid bilayer, while a polyelectrolyte multilayer film serves as an intermediate layer to facilitate the self-assembly of the lipid bilayer on the soft cushion. Quartz crystal microbalance studies show that, upon coming into contact with the polyelectrolyte film, vesicles fuse and rupture to yield a robust lipid bilayer. Fluorescence recovery after photobleaching confirms the formation of a membrane, while atomic force microscopy shows a low adhesion between the indenting probe and the bilayer. More importantly, in comparison to the solid-supported lipid bilayer, the response of this biomimetic system to nanoindentation demonstrates its increased mechanical stability and bendability when assembled on a soft cushion. Hence, the developed hydrogel-supported lipid bilayers can mimic biomechanical properties of cell membranes, which will enable scientists to study and to understand biophysicochemical interactions between cell membranes and extracellular entities.

Correction to "Cucurbit[8]uril as Nanocontainer in a Polyelectrolyte Multilayer Film: A Quantitative and Kinetic Study of Guest Uptake".

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionGet e-AlertsCorrection to “Cucurbit[8]uril as Nanocontainer in a Polyelectrolyte Multilayer Film: A Quantitative and Kinetic Study of Guest Uptake”Henning Nicolas, Bin Yuan, Jiawei Zhang, Xi Zhang, and Monika Schönhoff*Cite this: Langmuir 2017, 33, 19, 4879Publication Date (Web):May 5, 2017Publication History Published online5 May 2017Published inissue 16 May 2017https://doi.org/10.1021/acs.langmuir.7b00885Copyright © 2017 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views306Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (171 KB) Get e-AlertsGet e-Alerts Langmuir Get e-Alerts

Flexible and conductive multilayer films based on the assembly of PEDOT:PSS and water soluble polythiophenes

Flexible conductive polyelectrolyte multilayer films built upon anionic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and cationic poly(3-hexylthiophene)-based conjugated polyelectrolytes (P3HT-R) containing imidazolium, pyridinium and phosphonium ionic groups were prepared using electrostatic layer-by-layer assembly. Adsorbed amount of each polyelectrolyte strongly increases when divalent cations (Ba2+) are employed as electrolyte and when the rinsing step is avoided during the build-up. The electrical properties of these (P3HT-R/PEDOT:PSS)n multilayer films were then investigated using the van der Pauw method leading to an average conductivity of ∼2 S m−1. Semiconducting behavior of these organic coatings was demonstrated by the direct relationship between the conductivity and the temperature. (P3HT-R/PEDOT:PSS)n multilayer films exhibited p-type semiconducting behavior as showed by Seebeck measurements. Finally, these films were successfully deposited onto flexible polymer sheets and their conductivity was found to be not affected by applying a bending stress.

Highly Permeable Graphene Oxide/Polyelectrolytes Hybrid Thin Films for Enhanced CO2/N2 Separation Performance

Separation of CO2 from other gasses offers environmental benefits since CO2 gas is the main contributor to global warming. Recently, graphene oxide (GO) based gas separation membranes are of interest due to their selective barrier properties. However, maintaining selectivity without sacrificing permeance is still challenging. Herein, we described the preparation and characterization of nanoscale GO membranes for CO2 separation with both high selectivity and permeance. The internal structure and thickness of the GO membranes were controlled by layer-by-layer (LbL) self-assembly. Polyelectrolyte layers are used as the supporting matrix and for facilitating CO2 transport. Enhanced gas separation was achieved by adjusting pH of the GO solutions and by varying the number of GO layers to provide a pathway for CO2 molecules. Separation performance strongly depends on the number of GO bilayers. The surfaces of the multilayered GO and polyelectrolyte films are characterized by atomic force microscopy and scanning electron microscopy. The (poly (diallyldimethylammonium chloride) (PDAC)/polystyrene sulfonate (PSS)) (GO/GO) multilayer membranes show a maximum CO2/N2 selectivity of 15.3 and a CO2 permeance of 1175.0 GPU. LbL-assembled GO membranes are shown to be effective candidates for CO2 separation based on their excellent CO2/N2 separation performance.

Light-Controlled Selective Disruption, Multilevel Patterning, and Sequential Release with Polyelectrolyte Multilayer Films Incorporating Four Photocleavable Chromophores

We report photolabile polyelectrolyte multilayers (PEMs), produced by the layer-by-layer (LbL) approach, which comprise commercially available photoinert polyanions and photolabile polycations. Photochemical degradation of synthetic photolabile polycations renders these PEMs soluble in near neutral aqueous solutions. Taking advantage of the vast array of available photocleavable chromophores that absorb different wavelengths of light with different quantum yields of photolysis, we designed four photolabile polycations (P1–P4), each containing different photocleavable groups: dialkylaminocoumarin group (P1), different nitrobenzyl groups (P2 and P3), and methoxyphenacyl group (P4). PEMs containing different chromophores dissolved selectively under different irradiation conditions. Sequential photocontrolled dissolution of multilayers from a hybrid, quadruple-compartment LBL film was demonstrated using this approach, as was photolithographic patterning of films at multiple heights using different irradiation conditions and photomasks. We also demonstrated irradiation-selective, light-triggered release of guest fluorophores from microspheres coated with such PEMs.

Micro-Patterned Polystyrene Sheets as Templates for Interlinked 3D Polyelectrolyte Multilayer Microstructures

Polystyrene (PS) is currently mainly used as a sacrificial template during pattern release upon microcontact printing or for self-assembled flat free-standing films. We hereby present a method for creating 3D microstructured free-standing self-assembled polyelectrolyte multilayer (PEM) thin films. The approach presented utilizes a sacrificial microstructured PS template which can be coated with PEM thin films, whereby dissolution of the PS facilitates a free-standing 3D microstructured PEM film. The PS templating approach allows for omitting hot embossing on silicon masters, since PS templates can be prepared by drop casting on silicon masters. The prepared PEM film offers, if gold nanoparticles are incorporated, stimuli-responsive properties like light-induced chamber opening.

Effect of mono- and divalent ions on the formation and permeability of polyelectrolyte multilayer films

The layer by layer (LbL) sequential adsorption of oppositely charged polyelectrolytes is a simple tool to form ultrathin multilayer membranes with highly controlled properties. In our studies we have focused on the formation of multilayer films from the pair of synthetic, model polyelectrolytes: poly(allylamine hydrochloride) (PAH)/poly(4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC)/poly(4-styrenesulfonate) (PSS) in the presence of monovalent (NaCl) and divalent (MgCl2) ions solution with the same ionic strength. Quartz crystal microbalance (QCM) was used to determine the film mass. To examine barrier properties of the multilayers two electroactive probes were selected: positively charged hexaammineruthenium (III) chloride and equimolar solution of potassium hexacyanoferrate (II) and potassium hexacyanoferrate (III) of negative charge. We demonstrated that the mass/thickness of the film was larger when the polyelectrolytes were deposited in the presence of divalent ions. On the other hand, the permeability of the polymer films depended not only on the ionic strength, but also on the valence of the ions in the polyelectrolyte solution as well as the charge of the chosen electroactive probe.

Robust Guar Gum/Cellulose Nanofibrils Multilayer Films with Good Barrier Properties.

The pursuit of sustainable functional materials requires development of materials based on renewable resources and efficient fabrication methods. Hereby, we fabricated all-polysaccharides multilayer films using cationic guar gum (CGG) and anionic cellulose nanofibrils (i.e., TEMPO-oxidized cellulose nanofibrils, TOCNs) through a layer-by-layer casting method. This technique is based on alternate depositions of oppositely charged water-based CGG and TOCNs onto laminated films. The resultant polyelectrolyte multilayer films were transparent, ductile, and strong. More importantly, the self-standing films exhibited excellent gas (water vapor and oxygen) and oil barrier performances. Another outstanding feature of these resultant films was their resistance to various organic solvents including methanol, acetone, N,N-dimethylacetamide (DMAc) and tetrahydrofuran (THF). The proposed film fabrication process is environmentally benign, cost-effective, and easy to scale-up. The developed CGG/TOCNs multilayer films can be used as a renewable material for industrial applications such as packaging.

Label-Free Detection of DNA Hybridization Using a Reflective Microfiber Bragg Grating Biosensor With Self-Assembly Technique

A reflective fiber-optic biosensor based on microfiber Bragg grating (mFBG) for DNA hybridization detection using layer-by-layer self-assembly technology is demonstrated. By searching the wavelength separation of two well-defined resonances of mFBG in reflection, temperature-compensated refractive index measurement has been achieved. With the help of poly(ethylenimine) (PEI), poly(acrylic acid) (PAA), and single-stranded DNA (ssDNA) for the preparation of a polyelectrolyte multilayer film, more target DNA chains are absorbed by the (PEI/PAA)4(PEI/DNA)1 multilayer films immobilized on the surface of mFBG. The hybridization processes of the target ssDNA with the concentration of 1 μM have been monitored in real-time together with high specificity of the noncomplementary DNA target.

Buildup of hyperbranched polymer/alginate multilayers and their influence on protein adsorption and platelet adhesion

ABSTRACTA hyperbranched poly(methylene bisacrylamide–aminoethyl piperazine) (HPMA) and lactobionic acid modified hyperbranched poly(methylene bisacrylamide–aminoethyl piperazine) (LA–HPMA), namely, galactosylated HPMA, were assembled with alginate through the application of the layer‐by‐layer technique to fabricate polyelectrolyte multilayer (PEM) films. We monitored the assembly process to reveal the stepwise mass increase with a quartz crystal microbalance with the dissipation technique and by the reversal of the ζ potential. The thickness of PEMs assembled in solutions with different pHs was measured by spectroscopic ellipsometry; it showed a general decreasing tendency along with the pH increase. Postincubation in a buffer solution revealed that the multilayers possessed good stability with a thickness decrease from 5 to 15%. The PEMs showed a limited protein adsorption. Serum, bovine serum albumin, and fibrinogen were adsorbed onto the multilayers with a density within hundreds of nanograms per square centimeter to 1 μg/cm2 and showed a relatively smaller adsorption on the multilayers assembled at pH 9. The PEMs assembled with LA–HPMA showed the lowest adhesion and activation of platelets, regardless of the outmost layer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44769.

A supramolecular bioactive surface for specific binding of protein

Bioactive surfaces with immobilized bioactive molecules aimed specifically at promoting or supporting particular interactions are of great interest for application of biosensors and biological detection. In this work, we fabricated a supramolecular bioactive surface with specific protein binding capability using two noncovalent interactions as the driving forces. The substrates were first layer-by-layer (LbL) deposited with a multilayered polyelectrolyte film containing “guest” adamantane groups via electrostatic interactions, followed by incorporation of “host” β-cyclodextrin derivatives bearing seven biotin units (CD-B) into the films via host-guest interactions. The results of fluorescence microscopy and quartz crystal microbalance measurement demonstrated that these surfaces exhibited high binding capacity and high selectivity for avidin due to the high density of biotin residues. Moreover, since host-guest interactions are inherently reversible, the avidin-CD-B complex is easily released by treatment with the sodium dodecyl sulfate, and the “regenerated” surfaces, after re-introducing fresh CD-B, can be used repeatedly for avidin binding. Given the generality and versatility of this approach, it may pave a way for development of re-usable biosensors for the detection and measurement of specific proteins.

Infusing Lubricant onto Erasable Microstructured Surfaces toward Guided Sliding of Liquid Droplets.

Introducing a lubricant layer onto surfaces has emerged as a novel strategy to address a wide range of interface-related challenges. Recent studies of lubricant-infused surfaces have extended beyond repelling liquids to manipulating the mobility of fluids. In this study, we report a design of slippery surfaces based on infusing lubricant onto a polyelectrolyte multilayer film whose surface microstructures can be erased rapidly under mild condition. Unlike other lubricant-infused surfaces, the liquid movements (e.g., moving resistance and direction) on such surfaces can be manipulated via programming the surface microstructures beforehand. The work reported here offers a versatile design concept of lubricant-infused surfaces and may turn on new applications of this emerging class of bioinspired materials.