Manganese graft ionomer complexes (MaGICs) for dual imaging and chemotherapy.

Novel manganese graft ionomer complexes (MaGICs) that contain Mn ions complexed with a polyaminobisphosphonate-g-poly(ethylene oxide) (PEO) copolymer were developed for use as T-weighted contrast agents for MRI. The complexes exhibited good colloidal stability without release of free manganese and did not result in any in vitro toxicity against mouse hepatocytes. T relaxivities of the MaGICs at physiological pH were 2-10 times higher than that of a commercial manganese-based positive contrast agent.

Humidity-modulated phase control and nanoscopic transport in supramolecular assemblies.

Supramolecular assembly allows for enhanced control of bulk material properties through the fine modulation of intermolecular interactions. We present a comprehensive study of a cross-linkable amphiphilic wedge molecule based on a sulfonated trialkoxybenzene with a sodium counterion that forms liquid crystalline (LC) phases with ionic nanochannel structures. This compound exhibits drastic structural changes as a function of relative humidity (RH).

Properties, chemistry, and applications of the bioactive polysaccharide curdlan.

Curdlan is a bacterial polysaccharide that has been of significant recent interest due to its interesting and valuable rheological properties and its inherent bioactivity. The simple (1→3)-β-glucan homopolymeric, unbranched structure of curdlan is conducive to enhanced solubility relative to many other abundant natural polysaccharides, thus, providing alternatives for processing the polymer into desired shapes and formulations. At the same time, this relatively good solubility enables chemical modification under mild conditions, leading to a growing body of literature on derivative chemistry, structure-property relationships, and the potential for regioselective modification.

Cation and anion transport in a dicationic imidazolium-based plastic crystal ion conductor.

Here we investigate the organic ionic plastic crystal 1,2-bis[N-(N'-hexylimidazolium-d2(4,5))]ethane 2PF6(-) in one of its solid plastic crystal phases by means of multinuclear solid-state (SS) NMR and pulsed-field-gradient NMR diffusometry. We quantify distinct cation and anion diffusion coefficients as well as the Arrhenius diffusion activation energies (Ea) in this dicationic imidazolium-based plastic crystal. Our studies suggest a change in transport mechanism for the cation upon varying thermal and magnetic treatment (9.

Toward design of magnetic nanoparticle clusters stabilized by biocompatible diblock copolymers for T₂-weighted MRI contrast.

We report the fabrication of magnetic particles comprised of clusters of iron oxide nanoparticles, 7.4 nm mean diameter, stabilized by a biocompatible, amphiphilic diblock copolymer, poly(ethylene oxide-b-D,L-lactide). Particles with quantitative incorporation of up to 40 wt % iron oxide and hydrodynamic sizes in the range of 80-170 nm were prepared.

Improved microchip design and application for in situ transmission electron microscopy of macromolecules.

Understanding the fundamental properties of macromolecules has enhanced the development of emerging technologies used to improve biomedical research. Currently, there is a critical need for innovative platforms that can illuminate the function of biomedical reagents in a native environment. To address this need, we have developed an in situ approach to visualize the dynamic behavior of biomedically relevant macromolecules at the nanoscale.

Olefin cross-metathesis as a source of polysaccharide derivatives: cellulose ω-carboxyalkanoates.

Cross-metathesis has been shown for the first time to be a useful method for the synthesis of polysaccharide derivatives, focusing herein on preparation of cellulose ω-carboxyalkanoates. Commercially available cellulose esters were first acylated with 10-undecenoyl chloride, providing esters with olefin-terminated side chains. Subsequent cross-metathesis of these terminal olefin moieties with acrylic acid was performed in solvents including acrylic acid, THF, and CH2Cl2.

Quantitation of Complexed versus Free Polymers in Interpolyelectrolyte Polyplex Formulations.

The quantity of free polymer in a polymer/DNA complex (polyplex) formulation critically impacts its gene transfection efficiency, cellular uptake, and toxicity. In this study, the compositions of three interpolyelectrolyte polyplex formulations were quantified by a facile NMR method. Using careful integration of a 1D H NMR spectrum with a broad spectral width, the quantities of unbound polymer and polyplexes in solution were determined.

Synthesis and structure-property evaluation of cellulose ω-carboxyesters for amorphous solid dispersions.

The use of amorphous solid dispersions (ASDs) is an effective and increasingly widely used approach for solubility enhancement of drugs and drug candidates with poor aqueous solubility. Successful molecular dispersion of drugs in polymer matrices requires new polymers that are designed to meet all ASD requirements, including drug release and prevention of drug recrystallization in storage or from solution. We describe herein design and synthesis of a new series of cellulose ω-carboxyalkanoates for ASDs, by reaction of cellulose with long-chain diacids that have been monoprotected as benzyl esters at one end, and monoactivated as acid chlorides at the other.

Synthesis of amphiphilic 6-carboxypullulan ethers.

Hydrophobically modified polysaccharides that contain carboxyl groups possess exceptional features for drug delivery and other applications. Carboxyl groups were introduced at C-6 in the pullulan backbone by applying the well-established oxidation with TEMPO and NaOCl/NaBr. The oxidized product, 6-carboxypullulan, is even more water-soluble than pullulan.

Poly(trehalose): sugar-coated nanocomplexes promote stabilization and effective polyplex-mediated siRNA delivery.

When nanoparticles interact with their environment, the nature of that interaction is governed largely by the properties of its outermost surface layer. Here, we exploit the exceptional properties of a common disaccharide, trehalose, which is well-known for its unique biological stabilization effects. To this end, we have developed a synthetic procedure that readily affords a polymer of this disaccharide, poly(methacrylamidotrehalose) or "poly(trehalose)" and diblock copolycations containing this polymer with 51 repeat units chain extended with aminoethylmethacrylamide (AEMA) at three degrees of polymerization (n = 34, 65, and 84).

Alginate esters via chemoselective carboxyl group modification.

Alginates are (1→4) linked linear copolysaccharides composed of β-D-mannuronic acid (M) and its C-5 epimer, α-L-guluronic acid (G). Several strategies for synthesis of carboxyl modified alginate derivatives exist in the literature. Most of these however employ aqueous chemistries, such as carbodiimide coupling reactions.

Synthesis and Properties of Sulfonium Polyelectrolytes for Biological Applications.

Sulfonium macromolecules displayed for the first time nucleic acid binding and transfection in vitro. Conventional and controlled radical polymerization techniques coupled with subsequent alkylation generated a sulfonium homopolymer, poly(DMSEMA), and a sulfonium diblock copolymer, poly(OEG--DMSEMA). DNA gel shift assays probed the ability of sulfonium macromolecules to complex nucleic acids, and luciferase assays examined the transfection efficiency and cytotoxicity of both sulfonium macromolecules.

Effects of sulfate groups on the adsorption and activity of cellulases on cellulose substrates.

Pretreatment of lignocellulosic biomass with sulfuric acid may leave sulfate groups on its surface that may hinder its biochemical conversion. This study investigates the effects of sulfate groups on cellulase adsorption onto cellulose substrates and the enzymatic hydrolysis of these substrates. Substrates with different sulfate group densities were prepared from H2SO4- and HCl-hydrolyzed and partially and fully desulfated cellulose nanocrystals.

New insights for accurate chemically specific measurements of slow diffusing molecules.

Investigating the myriad features of molecular transport in materials yields fundamental information for understanding processes such as ion conduction, chemical reactions, and phase transitions. Molecular transport especially impacts the performance of ion-containing liquids and polymeric materials when used as electrolytes and separation media, with applications encompassing battery electrolytes, reverse-osmosis membranes, mechanical transducers, and fuel cells. Nuclear magnetic resonance (NMR) provides a unique probe of molecular translations by allowing measurement of all mobile species via spectral selectivity, access to a broad range of transport coefficients, probing of any material direction, and investigation of variable lengthscales in a material, thus, tying morphology to transport.

Solid dispersion of quercetin in cellulose derivative matrices influences both solubility and stability.

Amorphous solid dispersions (ASD) of quercetin (Que) in cellulose derivative matrices, carboxymethylcellulose acetate butyrate (CMCAB), hydroxypropylmethylcellulose acetate succinate (HPMCAS), and cellulose acetate adipate propionate (CAAdP) were prepared with the goal of identifying an ASD that effectively increased Que aqueous solution concentration. Crystalline quercetin and Que/poly(vinylpyrrolidinone) (PVP) ASD were evaluated for comparison. Powder X-ray diffraction (XRPD) and differential scanning calorimetry (DSC) were used to examine the crystallinity of ASDs, physical mixtures (PM) and quercetin.

Unraveling the local energetics of transport in a polymer ion conductor.

We compare diffusion activation energy measurements in a hydrated perfluorosulfonate ionomer and aqueous solutions of triflic acid. These measurements provide insight into water transport dynamics on sub-nm length scales, and gauge the contribution of the polymer sidechain terminal group. Future membrane materials design will hinge on detailed understanding of transport dynamics.

Chemical shifts of phenolic monomers in solution and implications for addition and self-condensation.

Alkali metal counter-cations alter the electron density of phenolates in solution by electrostatic interactions. This change in electron density affects their reactivity toward formaldehyde, hydroxymethylphenols, and isocyanates during polymerization. The electronic perturbation of phenolic model compounds in the presence of alkali metal hydroxides was investigated with (13)C and (1)H nuclear magnetic resonance in polar solvents relative to non-ionic controls, altering the chemical shifts of the model compounds, thus indicating changes in electron density using the chemical shift as a proxy.

Magnetic Nanoclusters with Hydrophilic Spacing for Dual Drug Delivery and Sensitive Magnetic Resonance Imaging.

Magnetic Block Ionomer Clusters () with hydrophilic ionic cores and nonionic coronas have been prepared that have ultrahigh transverse NMR relaxivities together with capacities for incorporating high concentrations of polar antibiotic payloads. Magnetite-polymer nanoparticles were assembled by adsorbing the polyacrylate block of an aminofunctional poly(ethylene oxide--acrylate) (HN-PEO--PAA) copolymer onto magnetite nanoparticles. The PEO blocks extended into aqueous media to keep the nanoparticles dispersed.

RAFT synthesis of ABA triblock copolymers as ionic liquid-containing electroactive membranes.

2-(Dimethylamino)ethyl acrylate (DMAEA) imparts versatile functionality to poly[Sty-b-(nBA-co-DMAEA)-b-Sty] ABA triblock copolymers. A controlled synthetic strategy minimized chain transfer reactions and enabled the preparation of high-molecular-weight ABA triblock copolymers with relatively narrow PDIs between 1.39 and 1.

Sample preparation and image acquisition using optical-reflective microscopy in the measurement of fiber orientation in thermoplastic composites.

A complete sample preparation procedure used to determine three-dimensional fiber orientation from optical micrographs of glass fiber-reinforced thermoplastic composites is presented. Considerations for elimination of irregularities in the elliptical footprints, contrast enhancement between fibers and surrounding polymer matrix, controlled-etching that allows the identification of small shadows where fiber recedes into the matrix, and topographical reconstruction of the elliptical footprint are described in the procedure. This procedure has produced high-quality optical micrographs employed to obtain accurate fiber orientation data for thermoplastic composites using the method of ellipses.

Phosphonium-containing diblock copolymers for enhanced colloidal stability and efficient nucleic acid delivery.

RAFT polymerization successfully controlled the synthesis of phosphonium-based AB diblock copolymers for nonviral gene delivery. A stabilizing block of either oligo(ethylene glycol(9)) methyl ether methacrylate or 2-(methacryloxy)ethyl phosphorylcholine provided colloidal stability, and the phosphonium-containing cationic block of 4-vinylbenzyltributylphosphonium chloride induced electrostatic nucleic acid complexation. RAFT polymerization generated well-defined stabilizing blocks (M(n) = 25000 g/mol) and subsequent chain extension synthesized diblock copolymers with DPs of 25, 50, and 75 for the phosphonium-containing block.

Crystallinity and motional dynamics study of a series of poly(arylene ether sulfone) segmented copolymer analogues.

Solid-state NMR spectroscopy was utilized to study the crystallinity and its correlation to the motional dynamics of a series of biphenol based poly(arylene ether sulfone) (PAES) copolymer analogues obtained by incorporating flexible aliphatic blocks. Introduction of a series of conformationally flexible aliphatic blocks into the rigid aromatic PAES blocks in the copolymer sequence had increased the crystallinity of the polymer matrix because the copolymer system with aliphatic blocks provided a decrease in the glass transition temperature (Tg) while maintaining a nonvariant melting temperature (Tm). Modified PAES copolymer systems with aliphatic blocks had yielded shorter (1)H T1 relaxation times and longer (1)H T1ρ relaxation times relative to the neat aromatic PAES copolymer.

Regioselective synthesis of cellulose ester homopolymers.

Regioselective synthesis of cellulose esters is extremely difficult due to the small reactivity differences between cellulose hydroxyl groups, small differences in steric demand between acyl moieties of interest, and the difficulty of attaching and detaching many protecting groups in the presence of cellulose ester moieties without removing the ester groups. Yet the synthesis of homopolymers of particular regioselectively substituted anhydroglucose esters is of critical importance to allow us to determine the analytical characteristics of such homopolymers, their structure-property relationships, and to obtain guidance that may ultimately enable identification and synthesis of cellulose derivatives with superior properties for various applications. We report here a new, general synthesis of both cellulose-2,6-O-diesters and cellulose-2,6-A-O-3-B-O-triesters with a high degree of regioselectivity, employing 3-O-allylcellulose as a key protected precursor.

MAG versus PEG: Incorporating a Poly(MAG) Layer to Promote Colloidal Stability of Nucleic Acid/"Click Cluster" Complexes.

Herein, we demonstrate the reversible addition-fragmentation chain transfer (RAFT) synthesis of an adamantane-conjugated glycopolymer, poly(2-methacrylamido-2-deoxy glucopyranose) (Ad-pMAG), as a hydrophilic coating to promote colloidal stability of click cluster-pDNA complexes in biological media. The Ad-pMAG is assembled via noncovalent interactions through inclusion complex formation between adamantane (Ad) and the β-cyclodextrin (βCD) core of the click cluster/pDNA and then further assembled with plasmid DNA to form polyplexes. Ad-pMAG incorporation was favorable over Ad-poly(ethylene glycol) (Ad-PEG) due to the enhanced colloidal stability of the click cluster/pDNA polyplex under physiological salt conditions at high N/P ratios.