Engineered hydrogen-bonded glycopolymer capsules and their interactions with antigen presenting cells

Hollow glycopolymer microcapsules were fabricated by hydrogen-bonded layer-by-layer (LbL) assembly, and their interactions with a set of antigen presenting cells (APCs), including dendritic cells (DCs), macrophages (MACs), and myeloid derived suppressor cells (MDSCs), were investigated. The glycopolymers were obtained by cascade postpolymerization modifications of poly(oligo(2-ethyl-2-oxazoline methacrylate)-stat-glycidyl methacrylate) involving the modification of the glycidyl groups with propargylamine and the subsequent attachment of mannose azide by copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC). Multilayer assembly of the hydrogen-bonding pair (glycopolymer/poly(methacrylic acid) (PMA)) onto planar and particulate supports (SiO2 particles, d = 1.16 μm) yielded stable glycopolymer films upon cross-linking by CuAAC. The silica (SiO2) particle templates were removed yielding hollow monodisperse capsules, as demonstrated by fluorescence and scanning electron microscopy. Cellular uptake studies using flow cytometry revealed the preferential uptake of the capsules by DCs when compared to MACs or MDSCs. Mannosylated capsules showed a cytokine independent cis-upregulation of CD80 specifically on DCs and a trans-downregulation of PDL-1 on MDSCs. Thus, the glycopolymer capsules may have potential as vaccine carriers, as they are able to upregulate costimulatory molecules for immune cell stimulation on DCs and at the same time downregulate immune inhibitory receptors on suppressor APC such as MDSCs

Impact of Minor Alloy Components on the Electrocapillarity and Electrochemistry of Liquid Metal Fractals

Exploring and controlling surface tension‐driven phenomena in liquid metals may lead to unprecedented possibilities for next‐generation microfluidics, electronics, catalysis, and materials synthesis. In pursuit of these goals, the impact of minor constituents within liquid alloys is largely overlooked. Herein, it is showed that the presence of a fraction of solute metals such as tin, bismuth, and zinc in liquid gallium can significantly influence their electrocapillarity and electrochemistry. The instability‐driven fractal formation of liquid alloy droplets is investigated with different solutes and reveals the formation of distinctive non‐branched droplets, unstable fractals, and stable fractal modes under controlled voltage and alkaline solution conditions. In their individually unique fractal morphology diagrams, different liquid alloys demonstrate significantly shifted voltage thresholds in transition between the three fractal modes, depending on the choice of the solute metal. Surface tension measurements, cycle voltammetry and surface compositional characterizations provide strong evidence that the minor alloy components drastically alter the surface tension, surface electrochemical oxidation, and oxide dissolution processes that govern the droplet deformation and instability dynamics. The findings that minor components are able to regulate liquid alloys’ surface tensions, surface element distributions and electrochemical activities offer great promises for harnessing the tunability and functionality of liquid metals

Insight into the structural, chemical and surface properties of proteins for the efficient ultrasound assisted co-encapsulation and delivery of micronutrients

Three different proteinaceous biopolymers, namely, egg white protein (EWP), soy protein isolate (SPI) and corn protein isolate (CPI) were used as protective shell materials to encapsulate micronutrients via an ultrasonic encapsulation technique. It was found that the physicochemical properties of the three protein-based matrices, including surface/total thiol (-SH) content, surface activity and denaturation temperature were the key factors that influenced the shell formation and stability. The EWP and CPI-shelled microcapsules reduced the degradation of the encapsulated vitamins by 20% and 40% after exposure to heating and UV-light irradiation. A double emulsion technique was further developed to co-encapsulate both oil- (vitamin A and D) and watersoluble (vitamin B, C and minerals) micronutrients. In-vitro digestion study showed that the proteinaceous microcapsules enable a sustained release of micronutrients, demonstrating their potential for food fortification applications

Characterization of Humic Acid from the River Bottom Sediments of Burigonga: Complexation Studies of Metals with Humic Acid

In order to characterize and study of the complexation of humic acid with metal ions, sediment samples were collected from five different places in the Buriganga River. The Humic Acids were extracted with the standard procedure provided by the International Humic Substance Society (IHSS). The extracted Humic Acids were characterized with FTIR, EDX and CHNS analyzer and a comparison between the standard and extracted HA was carried out. High C/N ratios (71.48-87.36) are observed in the CHNS analysis. A complexation study of the Humic Acid with iron (III) and cadmium (II) was also carried out using EDX, UV-Visible spectrophotometer and AAS techniques. The coagulation behavior was observed with Jar test. From the study, it was found that iron and cadmium could make a complex at pH 6.0 which was confirmed by EDX (Electron Dispersive x-ray)

Deciphering the role of quaternary n in o\u3csub\u3e2\u3c/sub\u3e reduction over controlled n-doped carbon catalysts

© 2020 American Chemical Society. Nitrogen-doped carbon catalysts prepared from amino-functionalized metal-organic frameworks [amino-MIL-101(Al)] were investigated for the oxygen-reduction reaction (ORR) with special emphasis on elucidating the role of different nitrogen species (e.g., pyridinic, pyrrolic, and quaternary N) as active catalytic sites. Careful optimization of pyrolysis temperature of the amino-MIL-101(Al) leveraged the synthesis of the catalysts with or without quaternary N functionalities. This allowed us to investigate the type(s) of N species responsible for the ORR catalysis and thus address the conflicting results reported so far regarding the pyridinic and/or quaternary N as active sites for ORR catalysis via four-electron transfer (4e-) pathways. Our findings suggest that the total nitrogen content in the catalysts does not influence the ORR, while the quaternary N sites exclusively catalyze the reduction of O2 via the 4e- transfer pathway in both alkaline and acidic electrolytes. Catalysts containing only pyridinic and pyrrolic N were observed to be ineffective for the ORR. The experimental results were further supported by computational simulation using the gradient-correlated density functional theory which revealed that the dissociative O2 adsorption (i.e., binding and cleavage of O═O bonds) is more favorable to quaternary N. Furthermore, calculations based on the relative surface potential energy, dipole moment, binding energy, and electron density indicate that the most stable structure of O2 chemisorption sites could only be achieved on the quaternary N carbon

Nanoengineering Particles through Template Assembly

The nanoengineering of particles is of interest for both fundamental and applied science. How particles are made substantially affects their properties and quality, and therefore usefulness. Disseminating current understanding of particle engineering can help facilitate the use of existing technologies, as well as guide future developments. Herein, we describe three methods used in our laboratory for the nanoengineering of particles, based on template assembly, and discuss important considerations for each. First, we describe the use of layer-by-layer assembly for depositing multilayered nanofilms on particle surfaces to generate core–shell particles and hollow capsules. Second, we detail the use of mesoporous silica templating for the engineering of porous polymer replica particles. Third, we describe how the coordination of phenolic compounds and metal ions can be used to fabricate thin films via metal–phenolic network formation on particle templates. We provide stepwise, easy-to-follow guides for each method and discuss commonly encountered challenges and obstacles, with considerations for how to alter these protocols to achieve desired particle properties. While we intend for these guides to be easily accessible to researchers new to particle engineering, we believe they can also provide useful insight to experienced researchers working in the field of engineering advanced particles

Nanoengineering Particles through Template Assembly

The nanoengineering of particles is of interest for both fundamental and applied science. How particles are made substantially affects their properties and quality, and therefore usefulness. Disseminating current understanding of particle engineering can help facilitate the use of existing technologies, as well as guide future developments. Herein, we describe three methods used in our laboratory for the nanoengineering of particles, based on template assembly, and discuss important considerations for each. First, we describe the use of layer-by-layer assembly for depositing multilayered nanofilms on particle surfaces to generate core–shell particles and hollow capsules. Second, we detail the use of mesoporous silica templating for the engineering of porous polymer replica particles. Third, we describe how the coordination of phenolic compounds and metal ions can be used to fabricate thin films via metal–phenolic network formation on particle templates. We provide stepwise, easy-to-follow guides for each method and discuss commonly encountered challenges and obstacles, with considerations for how to alter these protocols to achieve desired particle properties. While we intend for these guides to be easily accessible to researchers new to particle engineering, we believe they can also provide useful insight to experienced researchers working in the field of engineering advanced particles

Multiligand Metal–Phenolic Assembly from Green Tea Infusions

The synthesis of hybrid functional materials using the coordination-driven assembly of metal–phenolic networks (MPNs) is of interest in diverse areas of materials science. To date, MPN assembly has been explored as monoligand systems (i.e., containing a single type of phenolic ligand) where the phenolic components are primarily obtained from natural sources via extraction, isolation, and purification processes. Herein, we demonstrate the fabrication of MPNs from a readily available, crude phenolic sourcegreen tea (GT) infusions. We employ our recently introduced rust-mediated continuous assembly strategy to prepare these GT MPN systems. The resulting hollow MPN capsules contain multiple phenolic ligands and have a shell thickness that can be controlled through the reaction time. These multiligand MPN systems have different properties compared to the analogous MPN systems reported previously. For example, the Young’s modulus (as determined using colloidal-probe atomic force microscopy) of the GT MPN system presented herein is less than half that of MPN systems prepared using tannic acid and iron salt solutions, and the disassembly kinetics are faster (∼50%) than other, comparable MPN systems under identical disassembly conditions. Additionally, the use of rust-mediated assembly enables the formation of stable capsules under conditions where the conventional approach (i.e., using iron salt solutions) results in colloidally unstable dispersions. These differences highlight how the choice of phenolic ligand and its source, as well as the assembly protocol (e.g., using solution-based or solid-state iron sources), can be used to tune the properties of MPNs. The strategy presented herein expands the toolbox of MPN assembly while also providing new insights into the nature and robustness of metal–phenolic interfacial assembly when using solution-based or solid-state metal sources

Coordination-Driven Multistep Assembly of Metal–Polyphenol Films and Capsules

We report the assembly of metal-polyphenol complex (MPC) films and capsules through the sequential deposition of iron­(III) ions (Fe^(III)) and a natural polyphenol, tannic acid (TA), driven by metal–ligand coordination. Stable Fe^(III)/TA films and capsules were formed, indicating lateral and longitudinal cross-linking of TA by Fe^(III) in the film structure. Quartz crystal microbalance, ultraviolet–visible (UV-vis) spectrophotometry, and X-ray photoelectron spectroscopy were carried out to quantitatively analyze the film growth. A comparison of the MPC capsules prepared through multistep assembly with those obtained through one-step deposition, as reported previously [Ejima et al., <i>Science</i> <b>2013</b>, <i>341</i>, 154–156], reveals substantial differences in the nature of complexation and in their physicochemical properties, including permeability, stiffness, and degradability. This study highlights the importance of engineering MPC films with different properties through implementing different assembly methods