No abstract

Attractive protein−protein interactions in concentrated monoclonal antibody (mAb) solutions may lead to the formation of clusters that increase viscosity. Here, we propose an analytical model that relates mAb solution viscosity to clustering by accounting for the contributions of suboptimal mAb packing within a cluster and cluster fractal dimension. The influence of short-range, anisotropic attractions and longrange Coulombic repulsion on cluster properties is investigated by analyzing the clustersize distributions, cluster fractal dimensions, radial distribution functions, and static structure factors from a library of coarse-grained molecular dynamics simulations. The library spans a vast range of mAb charges and attractive interactions in solutions of varying ionic strength. We present a framework for combining the viscosity model and simulation library to successfully characterize the attraction, repulsion, and clustering of an experimental mAb in three different pH and cosolute conditions by fitting the measured viscosity or structure factor from small-angle X-ray scattering. At low ionic strength, the cluster-size distribution is impacted by strong charges, and both the viscosity and net charge or structure factor and net charge must be considered to deconvolute the effects of short-range attraction and long-range repulsion.

Nanofibers of polyaniline and oligoanilines of controlled molecular weight, e.g., tetraaniline, octaaniline, and hexadecaaniline, are synthesized using a versatile high ionic strength aqueous system that permits the use of H(2)O(2) with no added catalysts as a mild oxidizing agent. Films of oligoanilines deposited on plastic substrates show a robust and reversible chemiresistor response to NO(2) vapor at room temperature in ambient air (100-5 ppm).

Interfacial evaporation using porous hydrogels has demonstrated highly effective solar evaporation performance under natural sunlight to ensure an affordable clean water supply. However, it remains challenging to realize scalable and ready‐to‐use hydrogel materials with durable mechanical properties. Here, self‐assembled templating (SAT) is developed as a simple yet effective method to fabricate large‐scale elastic hydrogel evaporators with excellent desalination performance. The highly interconnected porous structure of the hydrogels with low tortuosity and tunable pore size enables high level of tunability on the water transport rate. With superior elasticity, the porous hydrogels are easy to process with a rapid shape recovery after being rolled, folded, and twisted over hundred times, and exhibit highly effective and stable evaporation with an evaporation rate of ≈2.8 kg m−2 h−1 and ≈90 % solar‐to‐vapor efficiency. It is anticipated that this SAT strategy, without the typical need for freeze‐drying, will accelerate the industrialization of hydrogel solar evaporators for practical applications.

The effects of a subclass of monoclonal antibodies (mAbs) on protein−protein interactions, formation of reversible oligomers (clusters), and viscosity (η) are not well understood at high concentrations. Herein, we quantify a short-range anisotropic attraction between the complementarity-determining region (CDR) and CH3 domains (K CDR-CH3 ) for vedolizumab IgG1, IgG2, or IgG4 subclasses by fitting small-angle X-ray scattering (SAXS) structure factor S eff (q) data with an extensive library of 12-bead coarse-grained (CG) molecular dynamics simulations. The K CDR-CH3 bead attraction strength was isolated from the strength of longrange electrostatic repulsion for the full mAb, which was determined from the theoretical net charge and a scaling parameter ψ to account for solvent accessibility and ion pairing. At low ionic strength (IS), the strongest short-range attraction (K CDR-CH3 ) and consequently the largest clusters and highest η were observed with IgG1, the subclass with the most positively charged CH3 domain. Furthermore, the trend in K CDR-CH3 with the subclass followed the electrostatic interaction energy between the CDR and CH3 regions calculated with the BioLuminate software using the 3D mAb structure and molecular interaction potentials. Whereas the equilibrium cluster size distributions and fractal dimensions were determined from fits of SAXS with the MD simulations, the degree of cluster rigidity under flow was estimated from the experimental η with a phenomenological model. For the systems with the largest clusters, especially IgG1, the inefficient packing of mAbs in the clusters played the largest role in increasing η, whereas for other systems, the relative contribution from stress produced by the clusters was more significant. The ability to relate η to shortrange attraction from SAXS measurements at high concentrations and to theoretical characterization of electrostatic patches on the 3D surface is not only of fundamental interest but also of practical value for mAb discovery, processing, formulation, and subcutaneous delivery.

No abstract

Nanocomposite films containing a high volume fraction (> 50vol%) of nanoparticles (NPs) in a polymer matrix are promising for their functionality and use as structural coatings, and also provide a unique platform to understand polymer behavior under strong confinement. Previously, we developed a novel technique to fabricate such nanocomposites at room temperature using solvent-driven infiltration of polymer (SIP) into NP packings. In the SIP process, a bilayer made of an underlying polymer film and a dense packing of NPs is exposed to solvent vapor which induces condensation of the solvent into the voids of the packing. The condensed solvent plasticizes the underlying polymer film, inducing polymer infiltration into the solvent-filled voids in the NP packing. In this work, we study the effect of confinement on the kinetics of SIP and the final partitioning of polymer into the interstices of the NP packing. We find that, while the dynamics of infiltration during SIP are strongly dependent on confinement, the final extent of infiltration is independent of confinement. The time for infiltration obeys a power law with confinement, as defined by the ratio of the chain size and the pore size. Qualitatively, the observed time scale is attributed to changes in concentration regimes as infiltration proceeds, which lead to shifting characteristic length scales in the system over time. When the concentration in the pore exceeds the critical overlap concentration, the characteristic length scale of the polymer is no longer that of the entire chain, but rather the correlation length, which is smaller than the pore size. Therefore, at long times, the extent of infiltration is independent of the confinement ratio. Furthermore, favorable surface interactions between the polymer and the nanoparticles enhance partitioning into the NP packing.

Understanding phase transitions of fluids confined within nanopores is important for a wide variety of technological applications. It is well known that fluids confined in nanopores typically demonstrate freezing-point depressions, ΔTf, described by the Gibbs-Thomson (GT) equation. Herein, we highlight and correct several thermodynamic inconsistencies in the conventional use of the GT equation, including the fact that the enthalpy of melting, ΔHm, and the solid-liquid surface energy, γ(SL), are functions of pore diameter, complicating their prediction. We propose a theoretical analysis that employs the Turnbull coefficient, originally derived from metal nucleation theory, and show its consistency as a more reliable quantity for the prediction of ΔTf. This analysis provides a straightforward method to estimate ΔTf of nanoconfined organic fluids. As an example, we apply this technique to ibuprofen, an active pharmaceutical ingredient (API), and show that this theory fits well to the experimental ΔTf of nanoconfined ibuprofen.