Scattering investigation of multiscale organization in aqueous solutions of native xanthan

The hierarchical morphology of xanthan solutions is analyzed by light and neutron scattering in a broad range of concentrations in order to connect their morphology to their well-documented dynamic properties. Static light scattering inside the semidilute regime is dominated by the form factor of individual xanthan chains while at higher concentrations chain interconnections appear to modify the low wave vector scattering. Dynamic light scattering reveals the self-similar nature of the solutions caused by interchain associations as intensity autocorrelation functions present power-law behaviour. Small angle neutron scattering is dominated by the fractal scattering from the formed network at intermediate length scales. At small length scales the rigid structure of xanthan is revealed and the molecular weight per unit length is extracted. No detectable morphological alterations for shear rates up to 1000 rad/s are observed revealing that the shear thinning behaviour of xanthan is related to the disruption of chain-chain associations

Complexation of Lysozyme with Adsorbed PtBS-b-SCPI Block Polyelectrolyte Micelles on Silver Surface

We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene)-bsodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the surface of silver. The adsorption kinetics are monitored by surface plasmon resonance and the surface morphology by atomic force microscopy. The micellar adsorption kinetics is dictated by two processes and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein binding and low resistance in loading. When the micellar adsorbed amount is high the situation is inversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface

Micelles from HOOC-PnBA- b -PAA-C12_{12} H15_{15} Diblock Amphiphilic Polyelectrolytes as Protein Nanocarriers

We investigate the potential of self-assembled nanostructures of the PnBA-b-PAA amphiphilic diblock polyelectrolyte as candidates for protein nanocarriers. Three PnBA-b-PAA copolymers with different molecular weights and PnBA/PAA weight ratios are tested. The system with the most well-defined core–shell micellar structure is chosen for complexation with lysozyme. Its solutions are found to contain well-defined core–shell micelles that are stable upon increase in solution salt content to physiological levels. Upon mixing with lysozyme we find that the protein globules accumulate preferably at the outer parts of the hydrated corona of the micelles. Increasing the protein concentration, intermicellar aggregation is enhanced in a controllable way. At high salt content the number of proteins per micelle is lower compared with the low salt content, which points to an interaction of predominantly electrostatic nature. While light scattering is very sensitive to complexation, small-angle neutron scattering is able to distinguish between the contributions from individual micelles and aggregates. This work demonstrates the use of scattering techniques to characterize protein–polymer interactions in multiple hierarchical levels

A sustainable bioprocess to produce bacterial cellulose (BC) using waste streams from wine distilleries and the biodiesel industry: evaluation of BC for adsorption of phenolic compounds, dyes and metals

BackgroundThe main challenge for large-scale production of bacterial cellulose (BC) includes high production costs interlinked with raw materials, and low production rates. The valorization of renewable nutrient sources could improve the economic effectiveness of BC fermentation while their direct bioconversion into sustainable biopolymers addresses environmental pollution and/or resource depletion challenges. Herein a green bioprocess was developed to produce BC in high amounts with the rather unexplored bacterial strain Komagataeibacter rhaeticus, using waste streams such as wine distillery effluents (WDE) and biodiesel-derived glycerol. Also, BC was evaluated as a bio-adsorbent for phenolics, dyes and metals removal to enlarge its market diversification.ResultsBC production was significantly affected by the WDE mixing ratio (0–100%), glycerol concentration (20–45 g/L), type of glycerol and media-sterilization method. A maximum BC concentration of 9.0 g/L, with a productivity of 0.90 g/L/day and a water holding capacity of 60.1 g water/g dry BC, was achieved at 100% WDE and ≈30 g/L crude glycerol. BC samples showed typical cellulose vibration bands and average fiber diameters between 37.2 and 89.6 nm. The BC capacity to dephenolize WDE and adsorb phenolics during fermentation reached respectively, up to 50.7% and 26.96 mg gallic acid equivalents/g dry BC (in-situ process). The produced BC was also investigated for dye and metal removal. The highest removal of dye acid yellow 17 (54.3%) was recorded when 5% of BC was applied as the bio-adsorbent. Experiments performed in a multi-metal synthetic wastewater showed that BC could remove up to 96% of Zn and 97% of Cd.ConclusionsThis work demonstrated a low-carbon approach to produce low-cost, green and biodegradable BC-based bio-adsorbents, without any chemical modification. Their potential in wastewater-treatment-applications was highlighted, promoting closed-loop systems within the circular economy era. This study may serve as an orientation for future research towards competitive or targeted adsorption technologies for wastewater treatment or resources recovery

Polyethylene Oxide Hydrogels Crosslinked by Peroxide for the Controlled Release of Proteins

Crosslinking of polyethylene oxide (PEO) using a peroxide in the melt is employed to synthesize soft hydrogels with the ability of controlled release of proteins. The viscoelastic properties of the swollen networks confirm the elastic nature of the synthesized material and they are in agreement with swelling characteristics. The hydrogels have mesh sizes at the nm scale as it is estimated by swelling measurements and measured by small angle neutron scattering (SANS). Diffusion of bovine serum albumin (BSA) and lysozyme (LYZ) out of the hydrogels is restricted by the presence of the network. The diffusion coefficient in the hydrogels is lower for BSA in comparison to LYZ, while in both cases it drops as the mesh size of the network becomes smaller. This study introduces the use of peroxide-crosslinked PEO networks in the investigation of protein transport within hydrogels, the development of hydrogel-based protein delivery patches and polymeric constructs

Formation of Uni-Lamellar Vesicles in Mixtures of DPPC with PEO-b-PCL Amphiphilic Diblock Copolymers

The ability of mixtures of 1.2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and the amphiphilic diblock copolymers poly (ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) to stabilize uni-lamellar nano-vesicles is reported. Small angle neutron scattering (SANS) is used to define their size distribution and bilayer structure and resolve the copresence of aggregates and clusters in solution. The vesicles have a broad size distribution which is compatible with bilayer membranes of relatively low bending stiffness. Their mean diameter increases moderately with temperature and their number density and mass is higher in the case of the diblock copolymer with the larger hydrophobic block. Bayesian analysis is performed in order to justify the use of the particular SANS fitting model and confirm the reliability of the extracted parameters. This study shows that amphiphilic block copolymers can be effectively used to prepare mixed lipid-block copolymer vesicles with controlled lamellarity and a significant potential as nanocarriers for drug delivery

The structure and dynamics of polyelectrolyte combs

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