Incorporation of an acrylic fatty acid derivative as comonomer for oxidative cure in acrylic latex

An acrylic fatty acid derivative (AcFAD) was evaluated as comonomer for promotion of oxidative cure in waterborne latexes. AcFAD was polymerized by solvent homopolymerization and copolymerization and by emulsion copolymerization, and the final products characterized. In the two polymerization processes, NMR analyses confirmed that the reaction occurred involving both the terminal acrylic double bond and the conjugated double bonds of the aliphatic chain. Compared with a reference acrylic latex, the results obtained after AcFAD incorporation showed a time-dependent increase in gel content and in solvent resistance of dry films. These were ascribed to oxidative cure and consequent self-crosslinking of the acrylic polymer, involving the conjugated double bonds in AcFAD side chains. Oxidative cure was also confirmed by FTIR analyses. In addition, reduction in minimum film-forming temperature evidenced that AcFAD has an internal plasticization effect during film formation. Incorporation of this comonomer in acrylic paint binder formulations constitutes a promising alternative to the use of volatile coalescing agents.     

Compound lipophilicity as a descriptor to predict binding affinity (1/K(m)) in mammals

In bioaccumulation models, biotransformation is one of the processes decreasing the concentration of chemicals in an organism. In order to be metabolized, a compound needs to bind to an enzyme. In this study, we derived relationships between binding affinity and lipophilicity, expressed as Log (1/K(m)) and Log K(ow), respectively. We focused on oxidations in mammals catalyzed by alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), flavin-containing monooxygenase (FMO), and cytochrome P450 (CYP) enzymes. For all regressions, 1/K(m) increased with compound K(ow), which can be understood from the tendency to biotransform lipophilic compounds into more polar, thus more easily excretable metabolites. Lipophilicity was relevant to the binding of most of the substrate classes of ADH, ALDH, and CYP. The resulting slopes had 95% Confidence Intervals covering the value of 0.63, typically noted in protein-water distribution (Log K(pw)) and Log K(ow) regressions. A reduced slope (0.2-0.3) was found for FMO: this may be due to a different reaction mechanism involving a nucleophilic attack. The general patterns of metabolism were mechanistically interpreted in terms of partitioning theory. Information on the overall principles determining biotransformation may be helpful in predicting metabolic rates.     

A caged progesterone analog alters intracellular Ca2+ and flagellar bending in human sperm

Progesterone is a physiological agonist for mammalian sperm, modulating its flagellar movement and facilitating the acrosome reaction. To study the initial action of progesterone, we developed a caged analog with a photosensitive group: nitrophenylethanediol, at position 20. Using this compound combined with stroboscopic illumination, we performed Ca(2)(+) imaging of human spermatozoa and analyzed the effects of progesterone on the intracellular Ca(2)(+) concentration ([Ca(2)(+)](i)) of beating flagella for the first time. We observed a transient [Ca(2)(+)](i) increase in the head and the flagellum upon photolysis of the caged progesterone and an increase in flagellar curvature. Detailed kinetic analysis revealed that progesterone elicits an increase in the [Ca(2)(+)](i) immediately in the flagellum (mid-piece and principal piece), thereafter in the head with a short time lag. This observation is different from the progesterone-induced Ca(2)(+) mobilization in mouse spermatozoa, where the Ca(2)(+) rise initiates at the base of the sperm head. Our finding is mostly consistent with the recent discovery that progesterone activates CatSper channels in human spermatozoa, but not in mouse spermatozoa.     

Double-Interlinked Colloidal Gels for Programable Fabrication of Supraparticle Architectures

Engineering colloidal gel inks with suitable features for fabricating robust supraparticle architectures through 3D printing may overcome the challenges of precisely controlling nanoparticles spatial distribution across multiple scales. Herein, oppositely charged proteinaceous-polymeric nanoparticles are combined to generate multi-component colloidal gel (COGEL) inks for fabricating supraparticle volumetric architectures. Leveraging on different nano-functional units, double-interlinked supraparticle assemblies are established via electrostatic interactions and on-demand covalent photocrosslinking. The COGEL inks are readily processable through in-air extrusion 3D printing, forming stable colloidal filaments. 3D printing yielded architecturally defined and robust supraparticle constructs that supported human stem cells attachment and cytoskeletal spreading. Owing to double interparticle interlinks the fabricated supraparticle constructs remained stable under physiological conditions and high/low shear stress, improving over the lower mechanical stability of single-interlinked platforms. Double-interlinked COGELs are processable via suspension 3D printing, unlocking the freeform volumetric writing of nanoparticle inks in protein-based hydrogels volume. The dual-interlinked COGEL technology opens new possibilities for generating user-defined supraparticle architectures with precise volumetric distribution of nanoparticles, both in-air and in-hydrogel platforms. The freedom to select modular multi-particle combinations, as well as the rapid 3D programming of COGEL inks, broadens the range of modular colloidal materials that can be fabricated for a variety of biomedical applications.     

Giant Polarization in Quasi-Adiabatic Ferroelectric Na+ Electrolyte for Solid-State Energy Harvesting and Storage

The advent of new solid-state energy storage devices to tackle the electrical revolution requires the usage of nonlinear behavior leading to emergent phenomena. The ferroelectric analyzed herein belongs to a family of electrolytes that allow energy harvesting and storage as part of its self-charging features when thermally activated. The Na_2.99Ba_0.005ClO electrolyte shows quasi-adiabatic behavior with a continuous increase in polarization upon cycling, displaying almost no hysteresis. The maximum polarization obtained at a weak electric field is giant and similar to the remanent polarization. It depends on the temperature with a pyroelectric coefficient of 5.37 C m⁻² °C⁻¹ from −5 to 46 °C. The emergence occurs via negative resistance and capacitance. The glass transition is found to have its origins in the sharp depolarization at 46 – 48 °C. Above –10 °C, at ≈ –5 °C, another thermal anomaly may rely on the topologic characteristics of the A_3–2xBa_xClO (A = Li, Na, K) glass electrolytes enabling positive feedback of the current of electrons throughout the surface of the inner cell. The phenomena may pave the way toward a better understanding of dipolar nanodomain fragile glasses with exceptional ferroelectric characteristics to architect energy harvesting and storage devices based on multivalent thermally activated Na⁺-ion-ion electrolytes.