Amphiphilic Macromolecules Research Articles

Liquid-Crystalline Ordering of Filaments Formed by Bidisperse Amphiphilic Macromolecules

Self-organization in mixtures of amphiphilic macromolecules with helical backbone having two different degrees of polymerization was studied by means of molecular dynamics simulations. It was found that in semi-dilute solutions bidispersity leads to increase of average aggregation number compared with monodisperse solutions and promotes formation of long wire-like aggregates, containing both short and long macromolecules. In concentrated mixtures, the structure of the aggregates is similar, they also contain both types of macromolecules and are nematically ordered. The values of orientational order parameter of both types of macromolecules in concentrated solutions are identical.

Specific Supramolecular Interaction Regulated Entropically Favorable Assembly of Amphiphilic Macromolecules

This article reports molecular interaction driven aqueous assembly of supramolecularly engineered amphiphilic macromolecules to cylindrical structure. Each polymer contains a single hydrophobic trialkoxybenzamide-linked naphthalene diimide (NDI) chromophore at the chain terminal as the supramolecular structure directing unit (SSDU). Irrespective of the structure of the appended hydrophilic polymer, H-bonding promoted J-aggregation among the NDI chromophore leads to the formation of thermally stable spherical micelle (critical aggregation concentration: 0.01–0.03 mM) which reorganizes to cylindrical micelle after a few hours. The reorganization time can be regulated by pH in the case of the anionic polymer as it affects the dynamics. Isothermal titration calorimetric (ITC) studies reveal positive ΔS values for assembly of all the polymers, reflecting the self-assembly process is favored by the entropy factor similar to the elegant examples in the biological domain. In contrast, a small molecule analogue of...

Nanotherapeutics Containing Lithocholic Acid-Based Amphiphilic Scorpion-Like Macromolecules Reduce In Vitro Inflammation in Macrophages: Implications for Atherosclerosis.

Previously-designed amphiphilic scorpion-like macromolecule (AScM) nanoparticles (NPs) showed elevated potency to counteract oxidized low-density lipoprotein (oxLDL) uptake in atherosclerotic macrophages, but failed to ameliorate oxLDL-induced inflammation. We designed a new class of composite AScMs incorporating lithocholic acid (LCA), a natural agonist for the TGR5 receptor that is known to counteract atherosclerotic inflammation, with two complementary goals: to simultaneously decrease lipid uptake and inhibit pro-inflammatory cytokine secretion by macrophages. LCA was conjugated to AScMs for favorable interaction with TGR5 and was also hydrophobically modified to enable encapsulation in the core of AScM-based NPs. Conjugates were formulated into negatively charged NPs with different core/shell combinations, inspired by the negative charge on oxLDL to enable competitive interaction with scavenger receptors (SRs). NPs with LCA-containing shells exhibited reduced sizes, and all NPs lowered oxLDL uptake to <30% of untreated, human derived macrophages in vitro, while slightly downregulating SR expression. Pro-inflammatory cytokine expression, including IL-1β, IL-8, and IL-10, is known to be modulated by TGR5, and was dependent on NP composition, with LCA-modified cores downregulating inflammation. Our studies indicate that LCA-conjugated AScM NPs offer a unique approach to minimize atherogenesis and counteract inflammation.

Fabrication of polymer capsules by an original multifunctional, active, amphiphilic macromolecule, and its application in preparing PCM microcapsules

Based on our recent discovery that D-PGMA solution showed excellent amphiphilic and reinitiation properties, an eco-friendly, facile and scalable method to prepare polymeric capsules was proposed.

A pH and salt dually responsive emulsion in the presence of amphiphilic macromolecules

A pH and salt dually responsive emulsion has been designed on the basis of a novel amphiphilic macromolecule. It was found that the water separation of an oil-in-water emulsion reached up to ∼60% after standing for 10 min at low pH. 2-(Diethylamino)ethyl methacrylate (DEA) residues were found to induce the macromolecules to protonate and to be hydrophilic at pH values between 2 and 6, resulting in dewetting from oil droplet surfaces in water. Besides, the macromolecules form aggregates with different structures at the water/oil interface, depending on the pH value or salt concentration of the emulsion system, enabling the system to be demulsified in response to the pH or salt stimulus. The experimental results also showed that with the addition of aluminium chloride at 100 mg L-1, the water separation was about 70% after 20 min. A possible mechanism with respect to demulsifying was proposed on the basis of an "ion bridge" among sodium acrylate (SA) residues, inducing the macromolecules to "cross-link" and become insoluble, and leading to oil/water separation. Furthermore, at a fixed pH of 5, addition of salt to the aqueous dispersion increased the degree of oil-water interfacial activity and batch emulsions were significantly unstable to coalesce at a low salinity of 25-50 mg L-1. This finding presents a new manipulation on emulsion stability and potential applications in the fields of oil recovery, wastewater treatment, sludge removal, and so on.

The Role of Hydrophobicity in the Cellular Uptake of Negatively Charged Macromolecules.

It is generally accepted that positively charged molecules are the gold standard to by-pass the negatively charged cell membrane. Here, it is shown that cellular uptake is also possible for polymers with negatively charged side chains and hydrophobic backbones. Specifically, poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene], a conjugated polyelectrolyte with sulfonate, as water-soluble functional groups, is shown to accumulate in the intracellular region. When the polymer hydrophobic backbone is dissolved using polyvinylpyrrolidone, an amphiphilic macromolecule, the cellular uptake is dramatically reduced. The report sheds light on the fine balance between negatively charged side groups and the hydrophobicity of polymers to either enhance or reduce cellular uptake. As a result, these findings will have important ramifications on the future design of targeted cellular delivery nanocarriers for imaging and therapeutic applications.

Degree of Unsaturation and Backbone Orientation of Amphiphilic Macromolecules Influence Local Lipid Properties in Large Unilamellar Vesicles.

Liposomes have become increasingly common in the delivery of bioactive agents due to their ability to encapsulate hydrophobic and hydrophilic drugs with excellent biocompatibility. While commercial liposome formulations improve bioavailability of otherwise quickly eliminated or insoluble drugs, tailoring formulation properties for specific uses has become a focus of liposome research. Here, we report the design, synthesis, and characterization of two series of amphiphilic macromolecules (AMs), consisting of acylated polyol backbones conjugated to poly(ethylene glycol) (PEG) that can serve as the sole additives to stabilize and control hydrophilic molecule release rates from distearoylphosphatidylcholine (DSPC)-based liposomes. As compared to DSPC alone, all AMs enable liposome formation and stabilize their colloidal properties at low incorporation ratios, and the AM's degree of unsaturation and hydrophobe conformation have profound impacts on stability duration. The AM's chemical structures, particularly hydrophobe unsaturation, also impact the rate of hydrophilic drug release. Course-grained molecular dynamics simulations were utilized to better understand the influence of AM structure on lipid properties and potential liposomal stabilization. Results indicate that both hydrophobic domain structure and PEG density can be utilized to fine-tune liposome properties for the desired application. Collectively, AMs demonstrate the potential to simultaneously stabilize and control the release profile of hydrophilic cargo.

Interfacial Films of Calcium Naphthenate: Influence of Polycardanol Structures

Calcium naphthenate deposition is a well-known challenge in South America oil fields. This type of scale results from the interfacial reaction of a specific naphthenic acids group with the divalent metal ions, more precisely Ca2+, found in produced water. To avoid/minimize precipitation of these solids, we have been used certain chemicals, while different chemicals acted by different mechanisms. In this work, amphiphilic macromolecules were produced by cardanol polyaddition (PCA) and polycondensation (PCC), characterized by Fourier transform infrared spectroscopy, 1H NMR, and size exclusion chromatography (SEC), and evaluated regarding their influence on the calcium naphthenate interfacial film formation, using model systems, by rheology tests. Naphthenic acids with a high concentration of tetra-protic naphthenic acids (ARNs) were extracted from an indigenous calcium naphthenate deposit and used to prepare model systems containing 25 mg/L of acids in toluene. Interfacial tension measurements of the model ...

Domains in mixtures of amphiphilic macromolecules with different stiffness of backbone

The domain structuring in concentrated mixtures of amphiphilic macromolecules with a different stiffness of backbone has been discovered and studied by means of molecular dynamics simulation. The macromolecules were composed of identical amphiphilic H-graft-P monomer units. In flexible macromolecules, the H-graft-P units are connected freely, whereas the stiff macromolecules have limitations imposed on torsion and bending angles and carry local helical structure. In solvent which is poor for the backbone, stiff macromolecules form filament clusters from few intertwined helical chains. The filaments can be aligned along each other sharing a common director or form a few liquid-crystalline domains oriented randomly with respect to each other. It was shown that increase of fraction of helical macromolecules leads to decrease of order parameter and its high variation over different samples due to the increase of length and polydispersity of persistent filaments.

Probing the Nanoscopic Thermodynamic Fingerprint of Paramagnetic Ligands Interacting with Amphiphilic Macromolecules.

Self-assembly of macromolecules with ligands is an intricate dynamic process that depends on a wide variety of parameters and forms the basis of many essential biological processes. We elucidate the underlying energetic processes of self-assembly in a model system consisting of amphiphilic core-shell polymers interacting with paramagnetic, amphiphilic ligand molecules from temperature-dependent continuous wave electron paramagnetic resonance (CW EPR) spectroscopy subsequent to spectral simulation. The involved processes as observed from the ligands’ point of view are either based on temperature-dependent association constants (KA,j,k) or dynamic rotational regime interconversion (IC) constants (KIC,j,k). The interconversion process describes a transition from Brownian (b1) towards free (b2) diffusion of ligand. Both processes exhibit non-linear van’t Hoff (lnK vs. T−1) plots in the temperature range of liquid water and we retrieve decisive dynamic information of the system from the energetic fingerprints of ligands on the nanoscale, especially from the temperature-dependent interconversion heat capacity (∆C°P,IC).

Highly Conductive Polypropylene-Graphene Nonwoven Composite via Interface Engineering.

Here we report a highly conductive polypropylene-graphene nonwoven composite via direct coating of melt blown polypropylene (PP) nonwoven fabrics with graphene oxide (GO) dispersions in N,N-dimethylformamide (DMF), followed by the chemical reduction of GO with hydroiodic acid (HI). GO as an amphiphilic macromolecule can be dispersed in DMF homogeneously at a concentration of 5 mg/mL, which has much lower surface tension (37.5 mN/m) than that of GO in water (72.9 mN/m, at 5 mg/mL). The hydrophobic PP nonwoven has a surface energy of 30.1 mN/m, close to the surface tension of GO in DMF. Therefore, the PP nonwoven can be easily wetted by the GO/DMF dispersion without any pretreatment. Soaking PP nonwoven in a GO/DMF dispersion leads to uniform coatings of GO on PP-fiber surfaces. After chemical reduction of GO to graphene, the resulting PP/graphene nonwoven composite offers an electrical conductivity of 35.6 S m-1 at graphene loading of 5.2 wt %, the highest among the existing conductive PP systems reported, indicating that surface tension of coating baths has significant impact on the coating uniformity and affinity. The conductivity of our PP/graphene nonwoven is also stable against stirring washing test. In addition, here we demonstrate a monolithic supercapacitor derived from the PP-GO nonwoven composite by using a direct laser-patterning process. The resulted sandwich supercapacitor shows a high areal capacitance of 4.18 mF/cm2 in PVA-H2SO4 gel electrolyte. The resulting highly conductive or capacitive PP/graphene nonwoven carries great promise to be used as electronic textiles.

Synthesis and Solution Properties of Hydrophobically Modified Polysaccharides

Hydrophobically modified polymers are amphiphilic macromolecules mainly constituted of a hydrophilic backbone and hydrophobic side groups. In aqueous solutions these polymers undergo inter- or intra-molecular hydrophobic association, which results in unusual properties useful for a number of practical applications. The areas of application of these polymers include associative thickeners for enhanced oil recovery, pharmaceuticals, personal care formulations, coatings, adhesives, surfactants, emulsifiers, etc. This review presents the analysis of a literature data on preparation of hydrophobically modified polysaccharides (HMP) and their properties in aqueous solutions. Some of the synthetic methods used for hydrophobic modification of non-ionic (cellulose ethers, starch, dextran, pullulan, etc.), anionic (carboxymethylcellulose, hyaluronic&lt;br /&gt;acid, pectic acid, alginic acid, heparin) and cationic olysaccharides (chitosan) are presented. The methodology used for the investigation of solution properties of hydrophobically modified polysaccharides is discussed. Special attention is paid to aggregate and micelle formation in solutions of hydrophobically&lt;br /&gt;modified polysaccharides, solubilization of hydrophobic compounds, their rheological properties and surface activity. The effects of polymer architecture (level of hydrophobic substitution, nature of hydrophobic groups, molecular weight of a hydrophilic backbone, etc.), concentration, temperature, presence of inorganic salts and organic solvents on solution properties of hydrophobically modified polysaccharides are discussed. Some applications of hydrophobically modified polysaccharides are briefly highlighted.

PEGylated BODIPY assembling fluorescent nanoparticles for photodynamic therapy

Two amphiphilic macromolecules were synthesized from polyethylene glycol monomethylether (PEG) and borondipyrrolmethene (BODIPY) via one-pot multicomponent Passerini reaction, and they could self-assemble into stable nanoparticles (NPs) in aqueous media. The optical properties, including fluorescence resonance energy transfer (FRET) were studied in detail. The obtained NPs possess good cytocompatibility, and could be used for living cell imaging and effective photodynamic therapy (PDT). These results shed light on one-pot synthesis of PEGylated fluorescent nanoparticles via multicomponent reaction for biomedical application.

Compartmentalization Technologies via Self-Assembly and Cross-Linking of Amphiphilic Random Block Copolymers in Water.

Orthogonal self-assembly and intramolecular cross-linking of amphiphilic random block copolymers in water afforded an approach to tailor-make well-defined compartments and domains in single polymer chains and nanoaggregates. For a double compartment single-chain polymer, an amphiphilic random block copolymer bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl, benzyl, and olefin pendants was synthesized by living radical polymerization (LRP) and postfunctionalization; the dodecyl and benzyl units were incorporated into the different block segments, whereas PEG pendants were statistically attached along a chain. The copolymer self-folded via the orthogonal self-assembly of hydrophobic dodecyl and benzyl pendants in water, followed by intramolecular cross-linking, to form a single-chain polymer carrying double yet distinct hydrophobic nanocompartments. A single-chain cross-linked polymer with a chlorine terminal served as a globular macroinitiator for LRP to provide an amphiphilic tadpole macromolecule comprising a hydrophilic nanoparticle and a hydrophobic polymer tail; the tadpole thus self-assembled into multicompartment aggregates in water.

Athero-inflammatory nanotherapeutics: Ferulic acid-based poly(anhydride-ester) nanoparticles attenuate foam cell formation by regulating macrophage lipogenesis and reactive oxygen species generation.

Future development of anti-oxidant formulations for atherosclerosis applications is essential to deliver an efficacious dose while limiting localized concentrations of pro-oxidants. In this study, we illustrate the potential of degradable ferulic acid-based polymer nanoparticles to control macrophage foam cell formation by significantly reducing oxLDL uptake through downregulation of scavenger receptors, CD-36, MSR-1, and LOX-1. Another critical finding is the ability of the degradable ferulate-based polymer nanoparticles to lower macrophage reactive oxygen species (ROS) levels, a precursor to apoptosis and plaque escalation. The degradable ferulic acid-based polymer nanoparticles hold significant promise as a means to alter the treatment and progression of atherosclerosis.

Creating Quasi Two-Dimensional Cluster-Assembled Materials through Self-Assembly of a Janus Polyoxometalate-Silsesquioxane Co-Cluster.

Clusters are an important class of nanoscale molecules or superatoms that exhibit an amazing diversity in structure, chemical composition, shape, and functionality. Assembling two types of clusters is creating emerging cluster-assembled materials (CAMs). In this paper, we report an effective approach to produce quasi two-dimensional (2D) CAMs of two types of spherelike clusters, polyhedral oligomeric silsesquioxanes (POSS), and polyoxometalates (POM). To avoid macrophase separation between the two clusters, they are covalently linked to form a POM-POSS cocluster with Janus characteristics and a dumbbell shape. This Janus characteristics enables the cocluster to self-assemble into diverse nanoaggregates, as conventional amphiphilic molecules and macromolecules do, in selective solvents. In our study, we obtained micelles, vesicles, nanosheets, and nanoribbons by tuning the n-hexane content in mixed solvents of acetone and n-hexane. Ordered packing of clusters in the nanosheets and nanoribbons were directly visualized using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) technique. We infer that the increase of packing order results in the vesicle-to-sheet transition and the change in packing mode causes the sheet-to-ribbon transitions. Our findings have verified the effectivity of creating quasi 2D cluster-assembled materials though the cocluster self-assembly as a new approach to produce novel CAMs.

Crystallization of Amphiphilic DNA C-Stars.

Many emerging technologies require materials with well-defined three-dimensional nanoscale architectures. Production of these structures is currently underpinned by self-assembling amphiphilic macromolecules or engineered all-DNA building blocks. Both of these approaches produce restricted ranges of crystal geometries due to synthetic amphiphiles' simple shape and limited specificity, or the technical difficulties in designing space-filling DNA motifs with targeted shapes. We have overcome these limitations with amphiphilic DNA nanostructures, or "C-Stars", that combine the design freedom and facile functionalization of DNA-based materials with robust hydrophobic interactions. C-Stars self-assemble into single crystals exceeding 40 μm in size with lattice parameters exceeding 20 nm.

Amphiphilic Polypeptoids Serve as the Connective Glue to Transform Liposomes into Multilamellar Structures with Closely Spaced Bilayers.

We report the ability of hydrophobically modified polypeptoids (HMPs), which are amphiphilic pseudopeptidic macromolecules, to connect across lipid bilayers and thus form layered structures on liposomes. The HMPs are obtained by attaching hydrophobic decyl groups at random points along the polypeptoid backbone. Although native polypeptoids (with no hydrophobes) have no effect on liposomal structure, the HMPs remodel the unilamellar liposomes into structures with comparable diameters but with multiple concentric bilayers. The transition from single-bilayer to multiple-bilayer structures is revealed by small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). The spacing between bilayers is found to be relatively uniform at ∼6.7 nm. We suggest that the amphiphilic nature of the HMPs explains the formation of multibilayered liposomes; i.e., the HMPs insert their hydrophobic tails into adjacent bilayers and thereby serve as the connective glue between bilayers. At higher HMP concentrations, the liposomes are entirely disrupted into much smaller micellelike structures through extensive hydrophobe insertion. Interestingly, these small structures can reattach to fresh unilamellar liposomes and self-assemble to form new two-bilayer liposomes. The two-bilayer liposomes in our study are reminiscent of two-bilayer organelles such as the nucleus in eukaryotic cells. The observations have significance in designing new nanoscale drug delivery carriers with multiple drugs on separate lipid bilayers and extending liposome circulation times with entirely biocompatible materials.

Supramolecularly Engineered Amphiphilic Macromolecules: Molecular Interaction Overrules Packing Parameters.

We report molecular interaction-driven self-assembly of supramolecularly engineered amphiphilic macromolecules (SEAM) containing a single supramolecular structure-directing unit (SSDU) consisting of an H-bonding group connected to a naphthalene diimide chromophore. Two such SEAMs, P1-50 and P2-50, having the identical chemical structure and hydrophobic/hydrophilic balance, exhibit distinct self-assembled structures (polymersome and cylindrical micelle, respectively) due to a difference in the H-bonding group (hydrazide or amide, respectively) of the single SSDU. When mixed together, P1-50 and P2-50 adopted self-sorted assembly. For either series of polymers, variation in the hydrophobic/hydrophilic balance does not alter the morphology reconfirming that self-assembly is primarily driven by directional molecular interaction which is capable of overruling the existing norms in packing parameter-dependent morphology control in an immiscibility-driven block copolymer assembly.

Supramolecularly Engineered Amphiphilic Macromolecules: Molecular Interaction Overrules Packing Parameters

AbstractWe report molecular interaction‐driven self‐assembly of supramolecularly engineered amphiphilic macromolecules (SEAM) containing a single supramolecular structure‐directing unit (SSDU) consisting of an H‐bonding group connected to a naphthalene diimide chromophore. Two such SEAMs, P1‐50 and P2‐50, having the identical chemical structure and hydrophobic/hydrophilic balance, exhibit distinct self‐assembled structures (polymersome and cylindrical micelle, respectively) due to a difference in the H‐bonding group (hydrazide or amide, respectively) of the single SSDU. When mixed together, P1‐50 and P2‐50 adopted self‐sorted assembly. For either series of polymers, variation in the hydrophobic/hydrophilic balance does not alter the morphology reconfirming that self‐assembly is primarily driven by directional molecular interaction which is capable of overruling the existing norms in packing parameter‐dependent morphology control in an immiscibility‐driven block copolymer assembly.