26 research outputs found
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 azideâalkyne cycloaddition (CuAAC). Multilayer assembly of the hydrogen-bonding pair (glycopolymer/poly(methacrylic acid) (PMA)) onto planar and particulate supports (SiO2 particles, d = 1.16 ÎŒm) 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 tensionâdriven phenomena in liquid metals may lead to unprecedented possibilities for nextâgeneration 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 instabilityâdriven fractal formation of liquid alloy droplets is investigated with different solutes and reveals the formation of distinctive nonâbranched 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 alloysâ 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 OâO 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
coreâshell 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 metalâphenolic 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
coreâshell 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 metalâphenolic 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 MetalâPhenolic Assembly from Green Tea Infusions
The synthesis of hybrid functional
materials using the coordination-driven assembly of metalâphenolic
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 sourceîžgreen
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
Youngâs 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 (âŒ50%) 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 metalâphenolic interfacial assembly when
using solution-based or solid-state metal sources
Coordination-Driven Multistep Assembly of MetalâPolyphenol Films and Capsules
We
report the assembly of metal-polyphenol complex (MPC) films
and capsules through the sequential deposition of ironÂ(III) ions (Fe<sup>(III)</sup>) and a natural polyphenol, tannic acid (TA), driven by
metalâligand coordination. Stable Fe<sup>(III)</sup>/TA films
and capsules were formed, indicating lateral and longitudinal cross-linking
of TA by Fe<sup>(III)</sup> in the film structure. Quartz crystal
microbalance, ultravioletâvisible (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>, 154â156], 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