Polyelectrolyte Multilayer Shell Research Articles

Nafion-Based Nanocarriers for Fluorine Magnetic Resonance Imaging.

The aim of our study was to develop a novel method for nanocarriers’ preparation as a fluorine magnetic resonance imaging (19F MRI)-detectable drug delivery system. The novelty of the proposed approach is based on the application of fluorinated polyelectrolyte Nafion as a contrast agent since typical MRI contrast agents are based on paramagnetic gadolinium or ferro/superparamagnetic iron oxide compounds. An advantage of using an 19F-based tracer comes from the fact that the 19F image is detected at a different resonance frequency than the 1H image. In addition, the close to zero natural concentration of 19F nuclei in the human body makes fluorine atoms a promising MRI marker without any natural background signal. That creates the opportunity to localize and identify only exogenous fluorinated compounds with 100% specificity. The nanocarriers were formed by the deposition of polyelectrolytes on nanoemulsion droplets via the layer-by-layer technique with the saturation approach. The polyelectrolyte multilayer shell was composed of Nafion, the fluorinated ionic polymer used for labeling by 19F nuclei, and poly-l-lysine (PLL). The surface of such prepared nanocarriers was further pegylated by adsorption of pegylated polyanion, poly-l-glutamic acid (PGA). The 19F MRI-detectable hydrophobic nanocarriers with an average size of 170 nm and a sufficient signal-to-noise ratio have been developed and optimized to be used for passive tumor targeting and drug delivery.

In vivo Studies on Pharmacokinetics, Toxicity and Immunogenicity of Polyelectrolyte Nanocapsules Functionalized with Two Different Polymers: Poly-L-Glutamic Acid or PEG.

BackgroundThe functionalization of a nanoparticle surface with PEG (polyethylene glycol) is an approach most often used for extending nanomaterial circulation time, enhancing its delivery and retention in the target tissues, and decreasing systemic toxicity of nanocarriers and their cargos. However, because PEGylated nanomedicines were reported to induce immune response including production of anti-PEG antibodies, activation of the complement system as well as hypersensitivity reactions, hydrophilic polymers other than PEG are gaining interest as its replacement in nanomaterial functionalization. Here, we present the results of in vivo evaluation of polyelectrolyte nanocapsules with biodegradable, polyelectrolyte multilayer shells consisting of poly-l-lysine (PLL) and poly-l-glutamic (PGA) acid as a potential drug delivery system. We compared the effects of nanocapsules functionalized with two different “stealth” polymers as the external layer of tested nanocapsules was composed of PGA (PGA-terminated nanocapsules, NC-PGA) or the copolymer of poly-l-lysine and polyethylene glycol (PEG-terminated nanocapsules, NC-PEG).MethodsNanocapsules pharmacokinetics, biodistribution and routes of eliminations were analysed postmortem by fluorescence intensity measurement. Toxicity of intravenously injected nanocapsules was evaluated with analyses of blood morphology and biochemistry and by histological tissue analysis. DNA integrity was determined by comet assay, cytokine profiling was performed using flow cytometer and detection of antibodies specific to PEG was performed by ELISA assay.ResultsWe found that NC-PGA and NC-PEG had similar pharmacokinetic and biodistribution profiles and both were eliminated by hepatobiliary and renal clearance. Biochemical and histopathological evaluation of long-term toxicity performed after a single as well as repeated intravenous injections of nanomaterials demonstrated that neither NC-PGA nor NC-PEG had any acute or chronic hemato-, hepato- or nephrotoxic effects. In contrast to NC-PGA, repeated administration of NC-PEG resulted in prolonged increased serum levels of a number of cytokines.ConclusionOur results indicate that NC-PEG may cause undesirable activation of the immune system. Therefore, PGA compares favorably with PEG in equipping nanomaterials with stealth properties. Our research points to the importance of a thorough assessment of the potential influence of nanomaterials on the immune system.

Fabrication of polyelectrolyte microspheres using porous manganese carbonate as sacrificial template for drug delivery application

Abstract

Encapsulation of camptothecin into pegylated polyelectrolyte nanocarriers

Camptothecin is a natural compound with excellent antitumor activity over a wide spectrum of human and animal cancers. However, the direct formulation is limited by insolubility in water and other biocompatible solvents, low stability in physiologic conditions, rapid plasma clearance and high systemic toxicity. In this study, pegylated polyelectrolyte nanocapsules were utilized to prepare camptothecin nanocarriers. Nanosize droplets containing the camptothecin were encapsulated in polyelectrolyte multilayer shells formed by sequential adsorption of polyelectrolytes technique. The nanocapsules were pegylated for passive targeting through the adsorption of the pegylated polyelectrolyte. The biological effects of encapsulated camptothecin on two tumor cell lines: mouse colon carcinoma cell line CT26-CEA and the mouse mammary carcinoma cell line 4T1 were studied. Obtained results suggest, that encapsulated drug, as well as free one, showed similar activity on the tested cells.

Pegylated polyelectrolyte nanoparticles containing paclitaxel as a promising candidate for drug carriers for passive targeting

Targeted drug delivery systems are of special importance in cancer therapies, since serious side effects resulting from unspecific accumulation of highly toxic chemotherapeutics in healthy tissues can restrict effectiveness of the therapy. In this work we present the method of preparing biocompatible, polyelectrolyte nanoparticles containing the anticancer drug that may serve as a vehicle for passive tumor targeting. The nanoparticles were prepared via direct encapsulation of emulsion droplets in a polyelectrolyte multilayer shell. The oil cores that contained paclitaxel were stabilized by docusate sodium salt/poly-l-lysine surface complex (AOT/PLL) and were encapsulated in shells formed by the LbL adsorption of biocompatible polyelectrolytes, poly-L-glutamic acid (PGA) and PLL up to 5 or 6 layers. The surface of the nanoparticles was pegylated through the adsorption of the pegylated polyelectrolyte (PGA-g-PEG) as the outer layer to prolong the persistence of the nanocarriers in the circulation. The synthesized nanoparticles were stable in cell culture medium containing serum and their average size was 100nm, which makes them promising candidates for passive targeted drug delivery. This notion was further confirmed by the results of studying the biological effects of nanoformulations on two tumor cell lines: mouse colon carcinoma cell line CT26-CEA and the mouse mammary carcinoma cell line 4T1. The empty polyelectrolyte nanoparticles did not affect the viability of the tested cells, whereas encapsulated paclitaxel retained its strong cytotoxic/cytostatic activity.

Encapsulation of clozapine in polymeric nanocapsules and its biological effects

Clozapine is an effective atypical antipsychotic drug that unfortunately exhibits poor oral bioavailability. Moreover, the clinical use of the compound is limited because of its numerous unfavorable and unsafe side effects. Therefore, the aim of the present study was the development of a new nanocarrier for a more effective clozapine delivery. Here, clozapine was encapsulated into polymeric nanocapsules (NCs). Polyelectrolyte multilayer shells were constructed by the technique of sequential adsorption of polyelectrolytes (LbL) using biocompatible polyanion PGA (Poly-l-glutamic acid, sodium salt) and polycation PLL (poly-l-lysine) on clozapine-loaded nanoemulsion cores. Pegylated external layers were prepared using PGA-g-PEG (PGA grafted by PEG (polyethylene glycol)). Clozapine was successfully loaded into the PLL-PGA nanocarriers (CLO-NCs) with an average size of 100nm. In vitro analysis of the interactions of the CLO-NCs with the cells of the mononuclear phagocytic system (MPS) was conducted. Cell biocompatibility, phagocytosis potential, and cellular uptake were studied. Additionally, the biodistribution and behavioral effects of the encapsulated clozapine were also studied. The results indicate that surface modified (by PEG grafting) polymeric PLL-PGA CLO-NCs are very promising nanovehicles for improving clozapine delivery.

Layer-by-layer nanoparticles for the targeted co-delivery of cisplatin and EZH2 siRNA in a model of high grade serous ovarian cancer

Event Abstract Back to Event Layer-by-layer nanoparticles for the targeted co-delivery of cisplatin and EZH2 siRNA in a model of high grade serous ovarian cancer Santiago Correa1, 2, Ki Young Choi2, 3, Aria Shi1 and Paula T. Hammond2, 3 1 MIT, Biological Engineering, United States 2 MIT, Koch Institute for Integrative Cancer Research, United States 3 MIT, Chemical Engineering, United States Introduction: Layer-by-layer (LbL) assembly is a powerful and established technique for creating composite, multifunctional nanoparticles through the controlled fabrication of nanoscale thin films composed of biologically relevant materials.[1][2][3] LbL particles exhibit multifunctional properties and stability in vivo, making them attractive drug carriers for the treatment of cancer.[4][5][6] This work aims to apply the multifunctional capabilities of LbL nanotechnology towards addressing the unique challenges posed by high-grade serous ovarian cancer (HGSOC). HGSOC represents roughly 70% of malignant epithelial ovarian cancers and is responsible for nearly two-thirds of ovarian cancer deaths[7][8][9]. The lethality of HGSOC is attributed to its striking capacity to develop resistance against platinum-based chemotherapy like cisplatin.[10] Here we seek to improve the therapeutic response to cisplatin by simultaneously silencing expression of the Polycomb protein enhancer of Zeste homolog 2 (EZH2), which is thought to contribute towards drug-resistance in ovarian cancer.[11][12] Leveraging LbL technology, cisplatin-loaded liposomes will be modified with a polyelectrolyte multilayer shell containing siRNA against EZH2. Co-delivery of the payload will be further facilitated by terminating the multilayer with the polysaccharide hyaluronan, which is known to target cancer cells by both pH dependent and ligand-specific mechanisms.[13] Materials and Methods: Figure 1. Drug-loaded liposomes will be sequentially exposed to polyelectrolytes of alternating charge to generate a film composed of poly(L-arginine) (PLA), siEZH2, and hyaluronan (HA). For preliminary experiments, cellular viability was determined over a range of cisplatin concentrations to calculate the IC50 value. Cells were either untreated before insult with cisplatin or transfected with siEZH2 72 hours prior. For uptake experiments, COV362 cells were treated with LbL nanoparticles at a final concentration of 20 pM and imaged live using a Nikon A1R confocal microscope at 24 hours post-treatment. The in vivo efficacy of the treatment will be evaluated in an orthotopic xenograft model in immune-compromised mice. All in vivo experiments will be conducted with the COV362 line, due to its genetic similarity with primary HGSOC.[14] Results and Discussion: Figure 2. Preliminary in vitro results reveal that silencing EZH2 using siRNA sensitizes COV362, SKOV3 and CAOV3 ovarian cancer cell lines to cisplatin (P<0.001 between cisplatin only and cisplatin plus siEZH2 groups, by ANOVA1 with the Bonferonni post-test). Figure 3. LbL nanoparticles formed from fluorescent polystyrene cores coated with PLA and HA were used to evaluate uptake by COV362 cells. Live cell imaging demonstrated high degree of nanoparticle internalization, consistent with the targeting capabilities attributed to HA coated particles. Cell membranes are in magenta, lysosomes are in red, and LbL nanoparticles are in green. Conclusion: Our preliminary data and existing literature provide a strong foundation for the success of this work. We have already demonstrated the sensitization of ovarian cancer cells to cisplatin by depleting EZH2. Furthermore, we have demonstrated that our LbL nanoparticles penetrate into ovarian cancer cells efficiently, indicating that they will be capable of delivering our proposed combination therapy. The authors thank the Koch Institute Swanson Biotechnology Center for technical support, specifically the Peterson nanotechnology, biopolymer, and flow cytometry facilities.

Preparation of the squalene-based capsules by membrane emulsification method and polyelectrolyte multilayer adsorption

The aim of work was to develop method of the formation of polyelectrolyte multilayer capsules with emulsion core containing squalen as hydrophobic phase, by membrane emulsification technique. We investigated influence of surfactant concentration on the size distribution of the formed emulsion droplets by membrane emulsifier. Depending on the concentration of surfactant AOT two regime in the formation of emulsion was observed. For concentration below 1×10−2M classical membrane emulsification occurred and the average size of emulsion drops agrees with the theoretical prediction that considers drop detachment from the membrane surface by the shear force and necking instability, above this concentration self-emulsification process was dominant. The obtained nanoemulsion were successfully encapsulated with polyelectrolyte multilayer shell formed from PAH and PSS polyelectrolytes. To demonstrate the possibility of encapsulation of hydrophobic drugs naproxen was encapsulated in squalene core nanocarriers (the size of ∼120nm).

Magnetically responsive liquid core polyelectrolyte nanocapsules

The aim of this work was to develop the method of preparation of magnetically responsive, loaded nanocapsules based on a liquid core encapsulation by polyelectrolyte (PE) multilayer adsorption. Magnetically responsive drug nanodelivery systems were prepared by the sequential adsorption of PEs (layer-by-layer technique) using biocompatible PEs (poly-l-lysine as the polycation and poly-glutamic acid as the polyanion). The model lipophilic drug, β-carotene, was successfully encapsulated in the liquid core while Fe3O4 nanoparticles were embedded into the PE multilayer shell. This magnetically responsive drug nanodelivery system may be a promising platform for future targeted therapies (e.g. cancer) or other biomedical applications (e.g. separation systems and diagnostics).

Cytotoxic activity of paclitaxel incorporated into polyelectrolyte nanocapsules

Nanoencapsulation is a promising solution for the delivery of chemotherapeutics to tumors. A method of preparation of drug-loaded nanocapsules based on the liquid core encapsulation by a sequential adsorption of a polyelectrolyte is described. An easily evaporative solvent, chloroform, was used as an oil phase. An interfacial complex formed with an oil-soluble, Food and Drug Administration-approved surfactant, and polycation poly-l-lysine (PLL) was used as a microemulsion stabilizer. A polyelectrolyte multilayer shell was constructed by a sequential adsorption of polyelectrolytes using biocompatible polyelectrolytes (PLL as a polycation and poly-l-glutamic acid as a polyanion). A hydrophobic anticancer agent, paclitaxel, was successfully encapsulated in the nanocarriers with the average size of 100 nm. In vitro analysis of the effects of nanoformulations was performed using a mouse colon carcinoma cell line CT26-CEA. Biocompatibility of the nanocapsules was evaluated using various biochemical assays. The results indicate that the cell viability was diminished by positively but not by negatively charged nanocarriers. Analysis of the cellular uptake of nanocapsules determined by flow cytometry and confocal microscopy confirmed their accumulation inside the cells. Encapsulated paclitaxel retains its cytotoxic/cytostatic activity; although its effects were weaker than those of the corresponding concentrations of the free drug. The generated nanocapsules seem to be a valuable vehicle for tumor drug delivery; although further work is needed to increase their overall activity.

Ion Transport Through Polyelectrolyte Multilayers

Polyelectrolyte multilayer (PEM) films and capsules loaded with ion-sensitive fluorophores can be used as ion-sensors for many applications including measurements of intracellular ion concentration. Previous studies have shown the influence of the PEM films/shells on the specific response of encapsulated ion-sensitive fluorophores. PEM shells are considered as semipermeable barriers between the environment and the encapsulated fluorophores. Parameters such as the time response of the encapsulated sensor can be affected by the porosity and charge of the PEM shell. In this study, the time response of an encapsulated pH-sensitive fluorophore towards pH changes in the surrounding environment is investigated. Furthermore, the conductance of PEM films for potassium ions is determined.

Functionalized biocompatible polyelectrolyte multilayers for drug delivery: In situ investigation of mechanical properties by dissipative quartz crystal microbalance

Nanostructured polymeric capsules have been applied in different fields, and specifically are regarded as promising for smart drug delivery applications. The physical–chemical and mechanical properties, and thus the permeability of the polyelectrolyte multilayer shell, play an important role in efficient delivery. Quartz crystal microbalance working in liquid has been used for the characterization of the buildup process and of the viscoelastic properties of biocompatible multilayers and of their functionalization by S-layer proteins. Optical and scanning electron microscopy have been used for the morphological characterization of nanostructured capsules obtained at physiological conditions by the assembly of the characterized multilayers onto spherical cores and by their subsequent removal. The proposed functionalized biocompatible capsules can be regarded as promising candidates for smart drug delivery applications.

Engineering of erythrocyte-based drug carriers: control of protein release and bioactivity

This work reports the fabrication of layer-by-layer (LbL) polyelectrolyte coated erythrocyte carriers that provide a simple means for controlling the burst and subsequent release of lysozyme. Erythrocytes were loaded with RITC-lysozyme as model compound via the hypotonic dialysis method. An encapsulation efficiency of 41.6% and a loading amount of 12.7 pg/cell was achieved. It is demonstrated that these carriers maintain their shape and integrity similar to natural erythrocytes after the encapsulation procedures, and achieve a uniform distribution of the encapsulated lysozyme. The erythrocyte carriers were fixed with glutaraldehyde and then successfully coated with biocompatible polyelectrolytes, poly-L: -lysine hydrobromide and dextran sulfate, using the LbL method. It is demonstrated that the release profile of the encapsulated macromolecule can be regulated by adjusting the number of polyelectrolyte layers. Furthermore by adjusting the concentrations of the cross linking agent the activity of the encapsulated lysozyme can be well preserved. These core-shell microcapsules, consisting of erythrocytes loaded with bioactive substances and coated with a polyelectrolyte multilayer shell, hold promise for a new type of biocompatible and biodegradable drug delivery system.

Variable on-demand release function of magnetoresponsive hybrid capsules

Magnetoresponsive hybrid capsules formed with polyelectrolytes, amphiphile bilayers and Fe3O4 nanoparticles were fabricated by a colloid-templating technique. Melamine–formaldehyde (MF) core particles with polyelectrolyte multilayer shell were prepared by layer-by-layer assembly. Fe3O4 nanoparticles were additionally deposited on the capsular surface. Hollow capsules were obtained by the removal of the MF core particles. Amphiphile bilayer was finally coated on the obtained hollow capsules. The deposition amount of the Fe3O4 nanoparticles is variable by changing the concentration of Fe3O4 dispersion using for preparation of capsules. Encapsulated dyes were released on-demand by irradiation with an alternating magnetic field, due to a phase transition in the amphiphile membrane, induced by heating of the magnetic nanoparticles. The release rate of the hybrid capsules was controllable through controlling the deposition amount of Fe3O4 nanoparticles on the capsules.

Raman imaging and photodegradation study of phthalocyanine containing microcapsules and coated particles

AbstractWe present the results of using Raman molecular imaging and atomic force microscopy (AFM) investigation of the composition, stability, and photodegradation of polyelectrolyte multilayer microcapsules and coated microparticles containing copper–phthalocyanine and iron–phthalocyanine. The influence of laser light on degradation of these phthalocyanine dyes embedded in the walls of polyelectrolyte multilayer capsules and shells of microparticles was studied by both AFM and Raman molecular imaging, but only the latter technique gave information on dynamics of photodegradation. Raman peak assignment was performed according to theoretical calculations. The degradation rate of phthalocyanine dyes is estimated from Raman signal measurements and a model is proposed to account for the degradation rate. Practical applications of our approach are outlined. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Kinetic stability of water-dispersed oil droplets encapsulated in a polyelectrolyte multilayer shell

The original theoretical model of polyelectrolyte adsorption onto water-dispersed colloid particles is extended to the system of polydisperse droplets of sunflower oil. Polycation (poly(allylamine hydrochloride)) and polyanion (poly(sodium 4-styrenesulfonate)) are taken in the theoretically projected concentrations to perform Layer-by-Layer assembly of a multilayer shell on the surface of oil droplets preliminary stabilized with a protein emulsifier (bovine serum albumin). The velocity of gravitational separation in suspension of encapsulated oil droplets is theoretically predicted and experimentally measured depending on the coating shell's thickness, aiming to clarify the mechanism to control over the separation process. Combining the theory and experimental data, the mass density of a polyelectrolyte multilayer shell assembled in a Layer-by-Layer fashion is obtained. Polyelectrolyte multilayer coated oil droplets are characterized by means of ζ-potential, and particle size measurements, and visualized by scanning electron microscopy.

Fabrication and mechanical properties of microchambers made of polyelectrolyte multilayers

A highly ordered array of hollow chambers ranging from 2 to 25 μm in size are fabricated using the layer-by-layer assembly of poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) on sacrificial templates with imprinted patterns of wells. Polyelectrolyte multilayer (PEM) chambers collapse if made of shells that are thinner than a critical value. This critical thickness of the shells is measured experimentally and is found to depend on the chambers geometry. Euler's model of critical stress is used to describe the collapse of the chambers. Adhesive contact of the chamber’s roof with the support is suggested as a major mechanism responsible for the collapse. Deformation of individual PEM chambers made of thicker shells is studied using a sharp indenter and varying the loading speed. At loading speeds of less than 0.33 mN s−1, the elastic theory describes the experimental data well for small deformations, yielding a Young's modulus of 4 ± 1 GPa for the PEM shell, while further deformation causes severe plastic buckling of the chamber. If the loading speed exceeds 0.33 mN s−1, the sharp indenter starts to pierce the chamber's roof and the size of the resulted hole can be precisely controlled by changing the penetration depth of the indenter. Filling the PEM chambers with oil micro-droplets by solvent-exchange method is also demonstrated.

Magnetoresponsive Smart Capsules Formed with Polyelectrolytes, Lipid Bilayers and Magnetic Nanoparticles

Magnetoresponsive smart capsules formed with polyelectrolytes, lipid bilayers and magnetic nanoparticles were fabricated by a colloid-templating technique. Melamine-formaldehyde core particles with polyelectrolyte multilayer shell were prepared by layer-by-layer assembly. Magnetite (Fe(3)O(4)) nanoparticles were selectively deposited on the capsular surface by aqueous solution deposition using Pd catalysts. Hollow capsules were obtained by the removal of the melamine formaldehyde core particles. Vibrating sample magnetometer (VSM) measurement of the capsules revealed the ferromagnetic behavior of deposited Fe(3)O(4) nanoparticles. Alternating magnetic field irradiation generates heat in the capsular dispersion. Additional lipid bilayer coating was carried out on the obtained hollow capsules. Dye molecules were loaded by exploiting the temperature-dependence of the lipid membrane permeability. An encapsulated dye was released on-demand by irradiation with an alternating magnetic field, due to a phase transition in the lipid membrane, induced by heating of the magnetic nanoparticles. The magnetically induced release is attributed to the phase transition of the lipid membrane, caused by heat of Fe(3)O(4) nanoparticles under magnetic stimuli, and not to rupture of the capsules.

Mesoporous Silica-Templated Assembly of Luminescent Polyester Particles

We report the template assembly of luminescent poly-3-hydroxybutyrate (PHB) particles doped with rare-earth complexes. The hydrophobic polymer, PHB, has been infiltrated into the nanopores of mesoporous silica (MS) particles in organic solvent. Because of the van der Waals interaction of the polymer chains, PHB loaded in the nanopores yields replicated particles following removal of the MS template. To prevent aggregation of the hydrophobic PHB particles in aqueous media, the PHB-loaded mesoporous silica particles were coated with a polyelectrolyte multilayer (PEM) shell through the layer-by-layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS). Following removal of the silica core, the PEM-coated PHB replicas were used to effectively coordinate rare-earth complexes (europium β-diketone, EuC). The EuC-loaded PHB replicas coated with PAH/PSS emit intense luminescence over a wide pH range (3−11) and for at least several months in aqueous solution, which is du...

Modulating the release kinetics through the control of the permeability of the layer-by-layer assembly: a review

The layer-by-layer (LbL) self-assembly technique has emerged as a simple and versatile method for coating biological and non-biological templates for various biomedical applications. A promising avenue of this technique lies in the encapsulation of drugs and other biological substances for controlled release. Fundamental studies of LbL assembly on flat surfaces have provided a sound understanding of film deposition theory and its pertinence to ionic and molecular transport and diffusion through polyelectrolyte multilayer (PEM) films. However, there is a lack of information on the permeability of three-dimensional PEM shell systems. In either PEM films or shells, it has been shown that drug release is a function of the ionic strength, pH and/or multilayer thickness. This report aims to provide an overview of the physicochemical parameters affecting the permeability of two- and three-dimensional multilayer shells, including ionic strength, layer number and pH. Furthermore, their synergic effect on loading and release of biologically active molecules from LbL multilayers are discussed.