A review of block polymer surfactants

Pluronic F68 Micelles as Carriers for an Anti-Inflammatory Drug: A Rheological and Scattering Investigation

Age-long ambition of medical scientists has always been advancement in healthcare and therapeutic medicine. Biomedical research indeed claims paramount importance in nanomedicine and drug delivery, and the development of biocompatible storage structures for delivering drugs stands at the heart of emerging scientific works. The delivery of drugs into the human body is nevertheless a nontrivial and challenging task, and it is often addressed by using amphiphilic compounds as nanosized delivery vehicles. Pluronics belong to a peculiar class of biocompatible and thermosensitive nonionic amphiphilic copolymers, and their self-assemblies are employed as drug delivery excipients because of their unique properties. We herein report on the encapsulation of diclofenac sodium within Pluronic F68 self-assemblies in water, underpinning the impact of the drug on the rheological and microstructural evolution of pluronic-based systems. The self-assembly and thermoresponsive micellization were studied through isothermal steady rheological experiments at different temperatures on samples containing 45 wt % Pluronic F68 and different amounts of diclofenac sodium. The adoption of scattering techniques, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), allowed for the description of the system features at the nanometer length scale, providing information about the characteristic size of each part of the micellar structures as a function of temperature and drug concentration. Diclofenac sodium is not a good fellow for Pluronic F68. The triblock copolymer aids the encapsulation of the drug, highly improving its water solubility, whereas diclofenac sodium somehow hinders Pluronic self-assembly. By using a simple empirical model and no fitting parameters, the steady viscosity can be predicted, although qualitatively, through the volume fraction of the micelles extracted through scattering techniques and compared to the rheological one. A tunable control of the viscous behavior of such biomedical systems may be achieved through the suitable choice of their composition.

Pluronic® triblock copolymer-based nanoformulations for cancer therapy: A 10-year overview

This paper provides a review of the literature on the use of Pluronic® triblock copolymers for drug encapsulation over the last 10 years. A special focus is given to the progress of drug delivery systems (e.g., micelles, liposomes, micro/nanoemulsions, hydrogels and nanogels, and polymersomes and niosomes); the beneficial aspects of Pluronic® triblock copolymers as biological response modifiers and as pharmaceutical additives, adjuvants, and stabilizers, are also discussed. The advantages and limitations encountered in developing site-specific targeting approaches based on Pluronic-based nanostructures in cancer treatment are highlighted, in addition to innovative examples for improving tumor cytotoxicity while reducing side effects.

Hydrocarbon-Based Statistical Copolymers Outperform Block Copolymers for Stabilization of Ethanol-Water Foams

Well-defined block copolymers have been widely used as emulsifiers, stabilizers, and dispersants in the chemical industry for at least 50 years. In contrast, nature employs amphiphilic proteins as polymeric surfactants whereby the spatial distribution of hydrophilic and hydrophobic amino acids within the polypeptide chains is optimized for surface activity. Herein, we report that polydisperse statistical copolymers prepared by conventional free-radical copolymerization can provide superior foaming performance compared to the analogous diblock copolymers. A series of predominantly (meth)acrylic comonomers are screened to identify optimal surface activity for foam stabilization of aqueous ethanol solutions. In particular, all-acrylic statistical copolymers comprising trimethylhexyl acrylate and poly(ethylene glycol) acrylate, P(TMHA-stat-PEGA), confer strong foamability and also lower the surface tension of a range of ethanol-water mixtures to a greater extent than the analogous block copolymers. For ethanol-rich hand sanitizer formulations, foam stabilization is normally achieved using environmentally persistent silicone-based copolymers or fluorinated surfactants. Herein, the best-performing fully hydrocarbon-based copolymer surfactants effectively stabilize ethanol-rich foams by a mechanism that resembles that of naturally-occurring proteins. This ability to reduce the surface tension of low-surface-energy liquids suggests a wide range of potential commercial applications.

Linear Block Copolymer Synthesis

Block copolymers form the basis of the most ubiquitous materials such as thermoplastic elastomers, bridge interphases in polymer blends, and are fundamental for the development of high-performance materials. The driving force to further advance these materials is the accessibility of block copolymers, which have a wide variety in composition, functional group content, and precision of their structure. To advance and broaden the application of block copolymers will depend on the nature of combined segmented blocks, guided through the combination of polymerization techniques to reach a high versatility in block copolymer architecture and function. This review provides the most comprehensive overview of techniques to prepare linear block copolymers and is intended to serve as a guideline on how polymerization techniques can work together to result in desired block combinations. As the review will give an account of the relevant procedures and access areas, the sections will include orthogonal approaches or sequentially combined polymerization techniques, which increases the synthetic options for these materials.

Interfacial Rearrangements of Block Copolymer Micelles Toward Gelled Liquid-Liquid Interfaces with Adjustable Viscoelasticity

Though amphiphiles are ubiquitously used for altering interfaces, interfacial reorganization processes are in many cases obscure. For example, adsorption of micelles to liquid-liquid interfaces is often accompanied by rapid reorganizations toward monolayers. Then, the involved time scales are too short to be followed accurately. A block copolymer system, which comprises poly(ethylene oxide)₁₁₀ -b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}₁₇₀ (i.e., PEO₁₁₀ -b-qPDPAEMA₁₇₀ with quaternized poly(diisopropylaminoethyl methacrylate)) is presented. Its reorganization kinetics at the water/n-decane interface is slowed down by electrostatic interactions with ferricyanide ([Fe(CN)₆ ]^3- ). This deceleration allows an observation of the restructuring of the adsorbed micelles not only by tracing the interfacial pressure, but also by analyzing the interfacial rheology and structure with help of atomic force microscopy. The observed micellar flattening and subsequent merging toward a physically interconnected monolayer lead to a viscoelastic interface well detectable by interfacial shear rheology (ISR). Furthermore, the "gelled" interface is redox-active, enabling a return to purely viscous interfaces and hence a manipulation of the rheological properties by redox reactions. Additionally, interfacial Prussian blue formation stiffens the interface. Such manipulation and in-depth knowledge of the rheology of complex interfaces can be beneficial for the development of emulsion formulations in industry or medicine, where colloidal stability or adapted permeability is crucial.

Merging bioresponsive release of insulin-like growth factor I with 3D printable thermogelling hydrogels

3D printing of biomaterials enables spatial control of drug incorporation during automated manufacturing. This study links bioresponsive release of the anabolic biologic, insulin-like growth factor-I (IGF-I) in response to matrix metalloproteinases (MMP) to 3D printing using the block copolymer of poly(2-methyl-2-oxazoline) and thermoresponsive poly(2-n-propyl-2-oxazine) (POx-b-POzi). For that, a chemo-enzymatic synthesis was deployed, ligating IGF-I enzymatically to a protease sensitive linker (PSL), which was conjugated to a POx-b-POzi copolymer. The product was blended with the plain thermogelling POx-b-POzi hydrogel. MMP exposure of the resulting hydrogel triggered bioactive IGF-I release. The bioresponsive IGF-I containing POx-b-POzi hydrogel system was further detailed for shape control and localized incorporation of IGF-I via extrusion 3D printing for future applications in biomedicine and biofabrication.

Poloxamer 188 as surfactant in biological formulations - An alternative for polysorbate 20/80?

Surfactants are used to stabilize biologics. Particularly, polysorbates (Tween® 20 and Tween® 80) dominate the group of surfactants in protein and especially antibody drug products. Since decades drug developers rely on the ethoxylated sorbitan fatty acid ester mixtures to stabilize sensitive molecules such as proteins. Reasons are (i) excellent stabilizing properties, and (ii) well recognized safety and tolerability profile of these polysorbates in humans, especially for parenteral applications. However, over the past decade concerns regarding the stability of these two polysorbates were raised. The search of alternatives with preferably less reservations concerning degradation and product quality reducing issues leads, among others, to poloxamer 188 (e.g. Kolliphor® P188), a nonionic triblock-copolymer surfactant. This review sums up our current knowledge related to the characterization and physico-chemical properties of poloxamer 188, its analytics and stability properties for biological formulations. Furthermore, the advantages and disadvantages as a suitable polysorbate-alternative for the stabilization of biologics are discussed.

Unusual Growth and Hydration Characteristics of Oil Solubilized Micelles in Aqueous Pluronic Systems

Lipophile induced modulations of self-assembly characteristics in aqueous Pluronic systems merit attention because of wide-ranging uses of Pluronics as solubilizing agents of lipophilic substances. In this paper, we report unusual evolutions of structural and hydration properties in lavender essential oil (LO) solubilized Pluronic P85 aqueous micellar systems as a function of micellar volume fraction and temperature. Our DLS, SANS, and viscometry studies show that the spherical-to-wormlike micellar structural transition observed in 1% P85 solutions upon solubilization of LO quite unexpectedly gets suppressed with increased P85 concentration to ≥5%. Detailed SANS studies reveal that the core sizes of the oil solubilized micelles cannot attain the threshold value required for the onset of structural transition at higher copolymer concentrations due to their progressive shrinking with an increase in P85 concentration. Oil solubilized P85 solutions show two cloud points and very interestingly exhibit micellar growth upon cooling to their lower cloud points. Steady state fluorescence studies explain this based on increasing dehydration of micellar corona with a decrease in temperature, very much opposite to what is observed in pure aqueous Pluronic systems. The results give new insight into viscous flow properties and low temperature storage possibilities of oil solubilized aqueous Pluronic systems.

Recent Advances in the Excipients Used for Modified Ocular Drug Delivery

In ocular drug delivery, maintaining an efficient concentration of the drug in the target area for a sufficient period of time is a challenging task. There is a pressing need for the development of effective strategies for drug delivery to the eye using recent advances in material sciences and novel approaches to drug delivery. This review summarizes the important aspects of ocular drug delivery and the factors affecting drug absorption in the eye including encapsulating excipients (chitosan, hyaluronic acid, poloxamer, PLGA, PVCL-PVA-PEG, cetalkonium chloride, and gelatin) for modified drug delivery.

Recent Advances in Polymer-Based Vaginal Drug Delivery Systems

The vagina has been considered a potential drug administration route for centuries. Most of the currently marketed and investigated vaginal formulations are composed with the use of natural or synthetic polymers having different functions in the product. The vaginal route is usually investigated as an administration site for topically acting active ingredients; however, the anatomical and physiological features of the vagina make it suitable also for drug systemic absorption. In this review, the most important natural and synthetic polymers used in vaginal products are summarized and described, with special attention paid to the properties important in terms of vaginal application. Moreover, the current knowledge on the commonly applied and innovative dosage forms designed for vaginal administration was presented. The aim of this work was to highlight the most recent research directions and indicate challenges related to vaginal drug administrations. As revealed in the literature overview, intravaginal products still gain enormous scientific attention, and novel polymers and formulations are still explored. However, there are research areas that require more extensive studies in order to provide the safety of novel vaginal products.

Nanocomposite gels of poloxamine and Laponite for β-Lapachone release in anticancer therapy

Nano-hybrid systems have been shown to be an attractive platform for drug delivery. Laponite® RD (LAP), a biocompatible synthetic clay, has been exploited for its ability to establish of strong secondary interactions with guest compounds and hybridization with polymers or small molecules that improves, for instance, cell adhesion, proliferation, and differentiation or facilitates drug attachment to their surfaces through charge interaction. In this work, LAP was combined with Tetronics, X-shaped amphiphilic PPO-PEO (poly (propylene oxide)-poly (ethylene oxide) block copolymers. β-Lapachone (BLPC) was selected for its anticancer activity and its limited bioavailability due to very low aqueous solubility, with the aim to improve this by using LAP/Tetronic nano-hybrid systems. The nanocarriers were prepared over a range of Tetronic 1304 concentrations (1 to 20% w/w) and LAP (0 to 3% w/w). A combination of physicochemical methods was employed to characterize the hybrid systems, including rheology, particle size and shape (DLS, TEM), thermal analysis (TG and DSC), FTIR, solubility studies and drug release experiments. In vitro cytotoxicity assays were performed with BALB/3T3 and MCF-7 cell lines. In hybrid systems, a sol-gel transition can occur below physiological temperature. BLPC exhibits the most significant increase in solubility in formulations with a high concentration of T1304 (over 10% w/w) and 1.5% w/w LAP, or systems with only LAP (1.5%), with a 50 and 100-fold increase in solubilisation, respectively. TEM images showed spherical micelles of T1304, which elongated into wormlike micelles with concentration (20%) and in the presence of LAP, a finding that has not been reported before. A sustained release of BLPC over 140 hours was achieved in one of the formulations (10% T1304 with 1.5% laponite), which also showed the best selectivity index towards cancer cells (MCF-7) over BALB/3T3 cell lines. In conclusion, BLPC-loaded T1304/LAP nano-hybrid systems proved safe and highly effective and are thus a promising formulation for anticancer therapy.

Highlights in poloxamer-based drug delivery systems as strategy at local application for vaginal infections

Infectious diseases related to the vagina include diseases caused by the imbalance of the vaginal flora and by sexually transmitted infections. Some of these present themselves as a public health problem due to the lack of efficient treatment that leads to their complete cure, and others due to the growing resistance to drugs used in therapy. In this sense, new treatment strategies are desirable, with vaginal administration rout being a great choice since can bypass first-pass metabolism and decrease drug interactions and adverse effects. However, it is worth highlighting limitations related to patient's discomfort at application time. Thereby, the use of poloxamer-based drug delivery systems is desirable due its stimuli-sensitive characteristic. Therefore, the present review reports a brief overview of poloxamer properties, biological behavior and advances in poloxamer applications in controlled drug release systems for infectious diseases related to the vagina treatment and prevention.

Adsorption rate constants of therapeutic proteins and surfactants for material surfaces

Adsorption of therapeutic proteins to material surfaces can be a pivotal issue in drug development, especially for low concentration products. Surfactants are used to limit adsorption losses. For each formulation component, surface adsorption is the result of a combination of its diffusion and surface adsorption rates. The latter are difficult to measure accurately because a depletion layer forms rapidly in the bulk solution above a bare surface, slowing down adsorption. Adapting flow conditions and local surface chemistry, we are able to minimize depletion limitations and measure apparent adsorption rate constants of three monoclonal antibodies, other proteins and surfactants with a hydrophobic surface. We show that surface adsorption rates scale with the molecular mass of the molecule, with polysorbates therefore showing thousand times slower rates than antibodies. Moreover, we observed that the desorption dynamic of polysorbates from a given hydrophobic surface depends on surface coverage, whereas this is not the case for Poloxamer 188. These novel contributions to surface adsorption dynamics enable a new perspective on the evaluation of drug surface compatibility and can, together with diffusion rates, be used to predict the protective potential of surfactants in given conditions.

Sequence of Polyurethane Ionomers Determinative for Core Structure of Surfactant-Copolymer Complexes

The core of micelles self-assembled from amphiphiles is hydrophobic and contains little water, whereas complex coacervate core micelles co-assembled from oppositely charged hydrophilic polymers have a hydrophilic core with a high water content. Co-assembly of ionic surfactants with ionic-neutral copolymers yields surfactant-copolymer complexes known to be capable of solubilizing both hydrophilic and hydrophobic cargo within the mixed core composed of a coacervate phase with polyelectrolyte-decorated surfactant micelles. Here we formed such complexes from asymmetric (PUI-A2) and symmetric (PUI-S2), sequence-controlled polyurethane ionomers and poly(N-methyl-2-vinylpyridinium iodide)29-b-poly(ethylene oxide)204 copolymers. The complexes with PUI-S2 were 1.3-fold larger in mass and 1.8-fold larger in radius of gyration than the PUI-A2 complexes. Small-angle X-ray scattering revealed differences in the packing of the similarly sized PUI micelles within the core of the complexes. The PUI-A2 micelles were arranged in a more ordered fashion and were spaced further apart from each other (10 nm vs. 6 nm) than the PUI-S2 micelles. Hence, this work shows that the monomer sequence of amphiphiles can be varied to alter the internal structure of surfactant-copolymer complexes. Since the structure of the micellar core may affect both the cargo loading and release, our findings suggest that these properties may be tuned through control of the monomer sequence of the micellar constituents.

Biofabrication of Hepatic Constructs by 3D Bioprinting of a Cell-Laden Thermogel: An Effective Tool to Assess Drug-Induced Hepatotoxic Response

A thermoresponsive Pluronic/alginate semisynthetic hydrogel is used to bioprint 3D hepatic constructs, with the aim to investigate liver-specific metabolic activity of the 3D constructs compared to traditional 2D adherent cultures. The bioprinting method relies on a bioinert hydrogel and is characterized by high-shape fidelity, mild depositing conditions and easily controllable gelation mechanism. Furthermore, the dissolution of the sacrificial Pluronic templating agent significantly ameliorates the diffusive properties of the printed hydrogel. The present findings demonstrate high viability and liver-specific metabolic activity, as assessed by synthesis of urea, albumin, and expression levels of the detoxifying CYP1A2 enzyme of cells embedded in the 3D hydrogel system. A markedly increased sensitivity to a well-known hepatotoxic drug (acetaminophen) is observed for cells in 3D constructs compared to 2D cultures. Therefore, the 3D model developed herein may represent an in vitro alternative to animal models for investigating drug-induced hepatotoxicity.

Direct-Write Deposition of Thermogels

The use of biocompatible hydrogels has widely extended the potential of additive manufacturing (AM) in the biomedical field leading to the production of 3D tissue and organ analogs for in vitro and in vivo studies.In this work, the direct-write deposition of thermosensitive hydrogels is described as a facile route to obtain 3D cell-laden constructs with controlled 3D structure and stable behavior under physiological conditions.

The coarse-grained models of poly(ethylene oxide) and poly(propylene oxide) homopolymers and poloxamers in big multipole water (BMW) and MARTINI frameworks

Polyethylene oxide (PEO) and poly(propylene oxide) (PPO), especially their tri-block copolymers PEO-PPO-PEO (poloxamers), have a broad range of applications in biotechnology and medical science. Understanding their specific interactions with biomembranes is the key to unveil the unique features of poloxamers either as membrane-healing or membrane pore-forming agents. Based on the coarse-graining convention of the MARTINI force field and the big multipole water (BMW) model, which has a three charged site topology and can reproduce the correct dipole moment of four-water clusters, we generated coarse-grained (CG) models with analytical and numerical potentials for PEO and PPO homopolymers and poloxamers in dilute solution. The effective bonded interaction potentials between CG beads were determined from the probability distributions of bond lengths, angles and dihedrals that are determined from atomistic simulations. The nonbonded interaction parameters were fine-tuned to reproduce the conformational properties of atomistic PEO and PPO homopolymers and poloxamers via extensive CG simulations of PEO and PPO homopolymers and poloxamers in a BMW water environment. The reported CG models provide a promising framework for a comprehensive understanding of the microstructural, conformational, and dynamic properties of poloxamers and their delicate interactions with other species in an explicit water environment.

Synthesis of poly(amide-thioether) with tunable hydrophilicity via thiolactone chemistry and its application in oil-in-oil emulsions

Oil-in-oil emulsions are ideal systems for water-sensitive reactions such as polymerizations and catalytic reactions, which has received extensive attention in recent years. The application of oil-in-oil emulsions has been developed slowly due to the limited types of surfactants and complicated synthesis process. Herein, we proposed a simple method to prepare poly(amide-thioether)-based surfactant for oil-in-oil emulsions via taking advantage of single-pot multicomponent and click characters of thiolactone chemistry. Using a combination of alkyl amine and acrylamide thiolactone, the aminolysis of thiolctone occurred first, generating thiol group in-situ, and then the generated thiol group would sequentially react with the double bonds of acrylamide to form polythioether in the presence of amine. The hydrophobicity of the surfactant could be effectively adjusted by the chain length of the alkyl amine and thus this polymer could serve as a promising surfactant for oil-in-oil emulsion. Notably, the emulsion types could be switched by changing the chain length of the alkyl amine. In addition, the effects of surfactant loading, volume ratio of oil phases, oil types on the size and stability of oil-in-oil emulsions were further investigated. It was demonstrated that the oil-in-oil emulsion stabilized by poly(amide-thioether)s kept stable after more than five months. Besides, we preliminarily explored the application of the oil-in-oil emulsion to prepare closed cell foam and porous particles via photo-initiated thiol-ene polymerization. It is believed that this super-stable oil-in-oil emulsion could offer more possibilities for highly potential water-sensitive systems.

Blinded Comparative Review of Lubricants Commonly Used for Split-Thickness Skin Graft Harvest

Lubricating agents facilitate effective harvesting of split-thickness skin grafts. Multiple agents, including water-based gel, mineral oil, glycerin, and poloxamer 188, have been utilized in this capacity. The agent selected is typically at the discretion of the provider and institution, as a single "ideal" lubricant remains to be objectively established. Furthermore, a recent discontinuation of Shur-Clens® Skin Wound Cleanser1 (a wound cleansing solution consisting of the surfactant poloxamer 188) has prompted the search for a suitable substitute for many providers. The purpose of this study is to directly compare five lubricants (including a novel surgical lubricant-based solution) to select a preferred agent. Four practitioners blindly tested five lubricants while harvesting a split-thickness skin graft on a porcine skin model (glycerin, mineral oil, saline, poloxamer 188, and a novel lubricant solution created with surgical lube and sterile water). The results were recorded on a Likert scale where 1 indicated poor performance and 5 indicated excellent performance. Data were pooled, and means were compared with analysis of variance and post hoc Tukey test. The cost of each lubricating solution was also reported. Mean scores for each of the solutions were as follows: dry control = 1.1 ± 0.1; glycerin = 2.62 ± 1.02, saline = 3.88 ± 0.81, mineral oil = 3.75 ± 1.00, novel water-based lubricant solution = 4.63 ± 0.71, and poloxamer 188 = 3.88 ± 0.81. All solutions were superior to dry control (P < .01). Glycerin was noted to have statistically lower scores than all of the other solutions (P < .01). The novel water-based surgical lubricant solution had significantly higher mean scores than both glycerin (P < .01) and mineral oil (P < .05). Each solution was compared according to dollars per 100cc with glycerin and Shur-Clens® representing the most expensive options at almost $3/100cc and saline the least expensive at less than $0.15/100cc. In a porcine skin model, the novel water-based surgical lubricant solution had the best performance. It was statistically superior to glycerin and mineral oil and was also found to be the most cost-effective option in terms of overall performance compared with relative cost. Glycerin had the worst performance with statistically lower scores than all other solutions. Glycerin was also found to be the least cost-effective due to a large discrepancy between high cost and low overall performance. Saline performed better than expected. These results may be skewed due to the inherently greasy nature of the butcher shop porcine skin, creating limitations and decreasing the fidelity of the model. In a search for the "ideal" lubricant, other models should be further studied.

Polymer-assisted drug sequestration from plasma protein by a surfactant with curtailed denaturing capacity

The capability of a surfactant to sequester a drug bound to plasma protein was investigated using steady-state and time-resolved spectroscopic techniques. Surfactants are known to denature protein, and hence are not suitable for the sequestration of a drug from protein. Herein, we show that the denaturing capacity of a surfactant is curtailed completely and its drug sequestration power is enhanced in the presence of biocompatible Pluronic micelles due to the formation of unique supramolecular assemblies. Further, our detailed studies indicate that the concentration of surfactant required for the sequestration of a drug is less than its critical micellar concentration (CMC). The extent of sequestration of drug by polymer-surfactant supramolecular assemblies can be tuned finely by controlling the concentration of surfactant. Detailed analysis showed that up to ∼85% sequestration of a drug from plasma protein could be achieved using a sub-CMC concentration of surfactant. Our results clearly show that controlled sequestration of a drug from plasma protein can be achieved with a reduction in the protein denaturing properties of surfactants.

Development of a rapid and reliable analytical method for screening poloxamer 188 for use in cell culture process

Poloxamer P188 is a common nonionic surfactant additive used in cell culture media as a cellular protectant from the hydrodynamic forces and shear stress during bioprocessing. Presence of a hydrophobic high molecular weight impurity contaminant has been shown to compromise its protective properties and lead to batch failure. In this work we present, a reliable, sensitive, and rapid analytical method to detect and quantify the contaminant impurity in poloxamer 188. This method replaces a laborious and time-consuming functional test in the form of a shake flask assay. The method is based upon reversed-phase liquid chromatography with charged aerosol detection, simple mobile phase compositions, and a three-step gradient. The method was optimized to resolve the impurity from the main P188 fraction in less than 10 min. Analytical method qualification and functional test comparison demonstrate equivalent or better high throughput impurity screening performance. Attempts to identify the impurity and establish suitable method positive control standards are also discussed.

The poly(propylene oxide-co-ethylene oxide) gradient is controlled by the polymerization method: determination of reactivity ratios by direct comparison of different copolymerization models

An investigation of the copolymerization of EO and PO by in situ¹H NMR spectroscopy reveals striking differences in the monomer gradient, depending on the polymerization method.

Adsorption of Pluronic Surfactants in Alkylene Carbonates on Silica

Adsorption of triblock Pluronic surfactants bearing poly(ethylene oxide) (PEO) chains of different lengths, L-62 (5 EO groups on each end), L-64 (13 EO groups on each end), and F-68 (79 EO groups on each end), on silica has been characterized using atomic force microscopy (AFM). The solvent used herein was a mixture of ethylene carbonate (EC) and propylene carbonate (PC). The three Pluronic surfactants were dissolved in the mixed solvent, with the PEO chain acting as a solvophilic group and the poly(propylene oxide) (PPO) chain acting as a solvophobic group. The approaching force curve measurements for the three Pluronics (at 10 mmol dm^-3) revealed repulsive forces from an apparent separation of 20-30 nm. The most solvophilic Pluronic surfactant with the longest PEO chain (F-68) showed continuously increasing repulsive interaction with decreasing separation. The Milner-Witten-Cates (MWC) theory described the repulsive force curve data of F-68, suggesting that F-68 forms a polymer brush on the silica surface. The retracting force curve measurements detected stretching forces for the three Pluronic systems. These stretching forces were observed more frequently for the L-62 system than for the F-68 system, but the pull-off distance was shorter for L-62 than for F-68.

Multilayer Assembly of Tannic Acid and an Amphiphilic Copolymer Poloxamer 188 on Planar Substrates toward Multifunctional Surfaces with Discrete Microdome-Shaped Features

Tannic acid (TA) is a natural polyphenol compound with a broad spectrum of biological activities, the most notable of which being antioxidation. Poloxamer 188 (P188), a synthetic triblock copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), is amphiphilic in nature and best known for its ability to seal structurally damaged cellular membranes. The integration of both substances onto planar substrates could bring a new option for multifunctional coatings that are advantageous for implantable biomedical devices. Here, we demonstrate the feasibility of multilayer assembly of TA/P188 toward such a coating based on hydrogen bonding between phenolic hydroxyls of TA and ether groups of P188, and the unique surface feature it generates. The interactions between these two compounds were studied both in solution and in substrate-supported layer-by-layer assembly. The multilayer assembly process exhibits an exponential growth pattern as characterized by UV-vis spectrophotometry and quartz crystal microbalance with dissipation. Morphologically unique, microdome-shaped surface features emerge and evolve with the number of layers assembled. Such features bring a reservoir function to this coating, as demonstrated by the loading of hydrophobic nile red dye. Furthermore, the presence of TA in the multilayers was revealed by silver nitrate staining, and its antioxidation activity was demonstrated through a 2,2-diphenyl-1-picryl-hydrazyl free-radical scavenging assay.

Pluronic-Based Mixed Polymeric Micelles Enhance the Therapeutic Potential of Curcumin

Curcumin is a naturally occurring constituent of turmeric that is a good substitute for synthetic medicines for the treatment of different diseases, due to its comparatively safer profile. However, there are certain shortcomings that limit its use as an ideal therapeutic agent. In order to overcome these drawbacks, we prepared novel curcumin-loaded mixed polymeric micelles using different biocompatible polymers by the thin-film hydration method. We investigated the critical micelle concentration and temperature, drug loading and encapsulation efficiency, and minimum inhibitory concentration by spectrophotometry. Surface morphology, stability, particle size, drug-polymer interaction, and physical state of the prepared formulations were investigated using scanning electron microscopy, zeta potential, particle size analyzer, Fourier-transform infrared spectroscopy, and X-ray diffraction, respectively. The drug loading and entrapment efficiency were significantly increased (P < 0.01) when curcumin was encapsulated with pluronic-based mixed polymeric micelles as compared to that of pluronic-based micelles alone. In vitro studies exhibited that pluronic-based mixed polymeric micelles significantly increased anticancer (P < 0.01), antimicrobial (P < 0.001), antioxidant (P < 0.001), and α-amylase inhibitory (P < 0.001) activities when compared to pure curcumin and/or pluronic-based micelles alone. These findings suggest that the formation of mixed polymeric micelles increases the stability and solubility of curcumin.

Synthesis of Zwitterionic Pluronic Analogs

Novel polymer amphiphiles with chemical structures designed as zwitterionic analogs of Pluronic block copolymers were prepared by controlled free radical polymerization of phosphorylcholine (PC) or choline phosphate (CP) methacrylate monomers from a difunctional poly(propylene oxide) (PPO) macroinitiator. Well-defined, water-dispersible zwitterionic triblock copolymers, or "zwitteronics", were prepared with PC content ranging from 5 to 47 mol percent and composition-independent surfactant characteristics in water, which deviate from the properties of conventional Pluronic amphiphiles. These PC-zwitteronics assembled into nanoparticles in water, with tunable sizes and critical aggregation concentrations (CACs) based on their hydrophilic-lipophilic balance (HLB). Owing to the lower critical solution temperature (LCST) miscibility of the hydrophobic PPO block in water, PC-zwitteronics exhibited thermoreversible aqueous solubility tuned by block copolymer composition. The chemical versatility of this approach was demonstrated by embedding functionality, in the form of alkyne groups, directly into the zwitterion moieties. These alkynes proved ideal for cross-linking the zwitteronic nanoparticles and for generating nanoparticle-cross-linked hydrogels using UV-initiated thiol-yne "click" chemistry.

Adsorption and Surface Properties of Mixtures of Fatty Acid Methyl Ester Ethoxylates and Sodium Dodecylbenzene Sulfonate

Adsorption behavior of mixtures of fatty acid methyl ester ethoxylates (FMEE) and sodium dodecylbenzene sulfonate (LAS) was studied and the adsorption parameters were calculated. The critical micelle concentration (CMC) and surface tension were measured by Wilhelmy plate method. Physicochemical properties of the mixtures were also investigated, such as cloud point and foaming property. The results show that the CMC of LAS was much higher than that of FMEE and decreased significantly by adding a low quantity of FMEE, while a powerful interaction between FMEE and LAS molecules in the micelles and the surface adsorption layer was exhibited. The cloud point and foaming property of the mixtures increased with increasing LAS content. An obvious change of the physical form of LAS solution by adding FMEE was observed.

Modeling and rescue of defective blood-brain barrier function of induced brain microvascular endothelial cells from childhood cerebral adrenoleukodystrophy patients

Background

X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene. 40% of X-ALD patients will convert to the deadly childhood cerebral form (ccALD) characterized by increased permeability of the brain endothelium that constitutes the blood–brain barrier (BBB). Mutation information and molecular markers investigated to date are not predictive of conversion. Prior reports have focused on toxic metabolic byproducts and reactive oxygen species as instigators of cerebral inflammation and subsequent immune cell invasion leading to BBB breakdown. This study focuses on the BBB itself and evaluates differences in brain endothelium integrity using cells from ccALD patients and wild-type (WT) controls.

Methods

The blood–brain barrier of ccALD patients and WT controls was modeled using directed differentiation of induced pluripotent stem cells (iPSCs) into induced brain microvascular endothelial cells (iBMECs). Immunocytochemistry and PCR confirmed characteristic expression of brain microvascular endothelial cell (BMEC) markers. Barrier properties of iBMECs were measured via trans-endothelial electrical resistance (TEER), sodium fluorescein permeability, and frayed junction analysis. Electron microscopy and RNA-seq were used to further characterize disease-specific differences. Oil-Red-O staining was used to quantify differences in lipid accumulation. To evaluate whether treatment with block copolymers of poly(ethylene oxide) and poly(propylene oxide) (PEO–PPO) could mitigate defective properties, ccALD-iBMECs were treated with PEO–PPO block copolymers and their barrier properties and lipid accumulation levels were quantified.

Results

iBMECs from patients with ccALD had significantly decreased TEER (2592 ± 110 Ω cm²) compared to WT controls (5001 ± 172 Ω cm²). They also accumulated lipid droplets to a greater extent than WT-iBMECs. Upon treatment with a PEO–PPO diblock copolymer during the differentiation process, an increase in TEER and a reduction in lipid accumulation were observed for the polymer treated ccALD-iBMECs compared to untreated controls.

Conclusions

The finding that BBB integrity is decreased in ccALD and can be rescued with block copolymers opens the door for the discovery of BBB-specific molecular markers that can indicate the onset of ccALD and has therapeutic implications for preventing the conversion to ccALD.

Electronic supplementary material

The online version of this article (10.1186/s12987-018-0094-5) contains supplementary material, which is available to authorized users.

Aggregation and Rheological Behavior of the Lavender Oil-Pluronic P123 Microemulsions in Water-Ethanol Mixed Solvents

The effect of lavender oil on aggregation characteristics of P123 in aqueous-ethanolic solutions is investigated systematically by DLS, SANS, and rheology. The solubilization capacity of the P123 based formulations toward Lavender oil increased by increasing P123 concentration. The study unveiled the importance of the short chain alcohol-ethanol, as solubilization enhancer. The apparent hydrodynamic radius (R_h) increased significantly with an increase in lavender oil concentration up to maximum oil solubilization capacity of the copolymer at a particular ethanol concentration. DLS measurements on 5, 10, and 15 wt% P123 in the presence of 25% ethanol revealed the presence of large-sized micellar clusters in addition to the oil swollen micelles. The core size (R_C), radius of hard sphere (R_HS), and aggregation number (N) obtained from SANS profiles showed considerable enhancement with the addition of lavender oil confirming penetration of oil inside the copolymer. Rheological studies showed that viscosity also increased significantly with the addition of lavender oil near the maximum loading limit of the P123 concentration. Quite interestingly, the sol-gel transition temperature displayed a strong dependence on both P123 as well as oil concentration and decreased almost linearly by increasing oil concentration. This study demonstrates the use of a biocompatible and temperature sensitive self-assembled P123 based formulation for lavender oil solubilization that can be beneficial in the cosmetic industry wherein controlled release of fragrances and so forth is demanded.