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Using small-angle neutron scattering (SANS), we examine the structure and conformational behavior of wheat arabinoxylan (AX) prepared at various concentrations in a sodium phosphate aqueous buffer. As for another major hemicellulose, xyloglucan, we observe a small number of large clusters surrounded by AX chains that behave exactly as a polymer in good solvent with a Flory exponent ν = 0.588. The fit of the data at high q -values to a standard worm-like chain model gives the persistence length l p = 45 Å and cross section of the chains 2 R c = 11-12 Å. In addition, using a dedicated modeling approach, we extract from the SANS data at the intermediate q -range the correlation length ξ of the solutions in the semidilute regime. The decay of ξ with concentration follows a scaling law that further confirms the self-avoiding statistical behavior of the AX chains. This first comprehensive study about the properties of water-soluble AX at different length scales may help in the development of products and processes involving AX as a substitute for fossil carbon molecules.

Self-sorting in functionalized dipeptide systems can be driven by the chirality of a single amino acid, both at a high pH in the micellar state and at a low pH in the gel state. The structures formed are affected to some degree by the relative concentrations of each component showing the complexity of such an approach. The structures underpinning the gel network are predefined by the micellar structures at a high pH. Here, we describe the systems prepared from two dipeptide-based gelators that differ only by the chirality of one of the amino acids. We provide firm evidence for self-sorting in the micellar and gel phases using small-angle neutron scattering and cryo-transmission electron microscopy (cryo-TEM), showing that complete self-sorting occurs across a range of relative concentrations.

Self-assembled aggregates formed by semidilute polyanion hyaluronan (hyaluronic acid, HA) and an oppositely charged surfactant tetradecyltrimethylammonium bromide (TTAB) in an aqueous phosphate-buffered saline (PBS) solution have been studied via light scattering (LS), small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM). The addition of 0-20 mM TTAB to a 27.7 mM (monomer, 1 wt %) HA solution (597 kDa) in PBS buffer leads to soluble complexes until phase separation occurs near charge equilibrium (>20 mM TTAB). While the viscosity remains rather constant, already small amounts of added TTAB lead to the formation of large globular superstructures, which are built in a hierarchical fashion from a locally threadlike structural arrangement of TTA micelles along the stiff HA chains, within the little changed HA network. These globular domains have radii of 60-100 nm and contain 500-700 TTA micelles, which means that they are very "fluffy" and composed of about 99% water. They do not grow in size or number upon further TTAB addition, but, instead, the additional TTA micelles form further threadlike complexes outside of the big globular domains. Such a type of polyelectrolyte-surfactant complexes (PESCs) has not been described before and has to be attributed to the particular properties of HA, which are high stiffness and relatively weak interactions with oppositely charged micelles due to having the charged carboxylic group close to the polysaccharide backbone. These findings demonstrate that the HA network structure in solution basically remains unaffected by complexation with an oppositely charged surfactant, explaining the unchanged rheological behavior and the formation of a unique PESC local "coacervate" structure within the HA hydrogel network.

Poly(lactide-co-glycolide)-block-poly(ethylene glycol) (PLGA-PEG) nanoparticles are commonly used as drug carriers in controlled drug release and targeting. To achieve predictable and clinically relevant volumes of drug distribution, nanoparticle size, surface charge, and especially composition and structure must be controlled. Understanding the internal structures within the particles is fundamentally important to explain differences in drug loading and variations in drug release rate. We prepared nanoparticles from ester-terminated PLGA-PEG polymers via nanoprecipitation, and studied the effects of altering the solvent-water miscibility (THF, acetone, and acetonitrile). Morphology, size, polydispersity, and ζ-potential of PLGA-PEG nanoparticles were characterized. Small angle neutron scattering measurements and fitted models revealed the internal nanoparticle structure: PLGA blocks of 7-9 nm are encapsulated inside a fairly dense PEG/water network in a fractal geometry. Particles with a larger PLGA block volume and higher PEG volume fraction in the particle interior result in greater retention of the hydrophilic anticancer drug carboplatin.

Copolymers based on poly(N-(2-hydroxypropylmethacrylamide)) with conjugated Doxrubicin are established as candidate anticancer therapeutics. Two HPMA-co-polymers (ca. 35000 g mol(-1)) with 2.5 and 8 mol % gly-phe-leu-gly peptidyl side-chain content have been modified using linear hydrocarbon and small aromatic molecules as simple drug mimics. This first contrast-variation SANS study on these systems demonstrates, combined with detailed modeling, a controlled switch from random coil to a more defined morphology induced by inclusion of a series of model drug mimics. Relatively small changes in drug-mimic type and loading can significantly alter the solution conformation, and we tentatively propose a helical type structure that is more or less tightly wound, depending on both hydrophobe loading and type. The results presented have important implications for understanding the influence of conjugate structure on solution properties, which is an important factor influencing biological and clinical activity.