Effect of sulfonation time on physicochemical, osteogenic, antibacterial properties and biocompatibility of carbon fiber reinforced polyether ether ketone.

The carbon fiber reinforced polyetheretherketone (CFR-PEEK) has been increasingly used in orthopedics dentistry due to its excellent biocompatibility and mechanical properties. However, the biological inertness and poor antibacterial activity limit its clinical applications. This paper focused on the performances of CFR-PEEK with porous morphology that were exposed to different sulfonation periods (1, 3, 5, and 10 min, corresponding to CP-S1, CP-S3, CP-S5, and CP-S10, respectively). Residual sulfuric acid was removed by acetone rinsing, NaOH immersion, and hydrothermal treatment before in vitro and in vivo studies. The results showed some significant difference in the physicochemical properties, including energy dispersive X-ray spectroscopy (EDS) map of sulfur atoms, X-ray photoelectron spectroscopy (XPS) of valences of sulfur ions, Fourier transformation infrared spectroscopy (FTIR), hydrophilicity, hardness, and elastic modulus among CP-S3, CP-S5, and CP-S10. However, CP-S5 and CP-S10 were more effective in promoting the proliferation, adhesion, and osteogenic differentiation of seeded bone mesenchymal stem cells (BMSCs) and growth inhibition of S. aureus and P. gingivalis compared with other groups. Furthermore, the CP-S5 and CP-S10 samples achieved better cranial bone repair than the non-sulfonation group in a rat model. Therefore, it can be inferred that both 5 and 10 min are viable sulfonation durations for 30% CFR-PEEK. These findings provide a theoretical basis for developing CFR-PEEK for clinical applications.

Reversible Regulating the Substrate Specificity of Enzymes in Microgels by a Phase Transition in Polymer Networks.

Here, we report a distinct approach for regulating the substrate specificity of enzymes immobilized in microgels by a phase transition in polymer networks. The finding is demonstrated on glucose oxidase that is immobilized in thermoresponsive poly(N-isopropylacrylamide)-based microgels. Laser light scattering and enzymatic oxidation tests indicate that the broadened specificity appears at low temperatures, at which the gel matrix is in the relatively swollen state relative to its state at microgel synthesis temperature; upon heating to the relative higher temperatures, the gel matrix is not able to shrink further that offers a tight space in which the enzyme resides to retain high glucose specificity. It is proposed that polymer phase transition in the gel matrix mainly alter protein gates that control passage of substrates into active sites, making them open or close to a certain extent that enable reversible regulating the substrate specificity. The finding is also observed on bulk gels under a rational design, making it of potential interest in enzymatic biofuel cell applications.

Recent Progress in Pd-Based Nanocatalysts for Selective Hydrogenation.

Selective hydrogenation plays an important role in the chemical industry and has a wide range of applications, including the production of fine chemicals and petrochemicals, pharmaceutical synthesis, healthcare product development, and the synthesis of agrochemicals. Pd-based catalysts have been widely applied for selective hydrogenation due to their unique electronic structure and ability to adsorb and activate hydrogen and unsaturated substrates. However, the exclusive and comprehensive summarization of the size, composition, and surface and interface effect of metal Pd on the performance for selective hydrogenation is still lacking. In this perspective, the research progress on selective hydrogenation using Pd-based catalysts is summarized. The strategies for improving the catalytic hydrogenation performance over Pd-based catalysts are investigated. Specifically, the effects of the size, composition, and surface and interfacial structure of Pd-based catalysts, which could influence the dissociation mode of hydrogen, the adsorption, and the reaction mode of the catalytic substrate, on the performance have been systemically reviewed. Then, the progress on Pd-based catalysts for selective hydrogenation of unsaturated alkynes, aldehydes, ketones, and nitroaromatic hydrocarbons is revealed based on the fundamental principles of selective hydrogenation. Finally, perspectives on the further development of strategies for chemical selective hydrogenation are provided. It is hoped that this perspective would provide an instructive guideline for constructing efficient heterogeneous Pd-based catalysts for various selective hydrogenation reactions.

New 3D Porous Silver Nanopolycluster as a Highly Effective Supercapacitor Electrode: Synthesis and Study of the Optical and Electrochemical Properties.

A high-nucleus silver nanopolycluster as a new type of silver-based polymer supercapacitor (SSc) by a simple and single-step synthesis process was designed and synthesized. The structural, optical, and electrochemical properties of SSc-2 were determined. This highly stable conductive 3D nanopolycluster shows great cycling stability, large capacity, and high energy density without any modification or doping process and so acts as an excellent SSc (412 F g-1 at 1.5 A g-1). In addition, there was a stable cycling performance (94% capacitance) following 7000 cycles at 3 A g-1 current density. The presence of fluorinated groups, 3D expansion of high-nucleus metallic clusters, and porosity are the advantages of SSc-2 that lead to stability, conductivity, and high capacity, respectively. These results lead to the development of a novel kind of SSc by overcoming the low conductivity and limited capacity challenges without any modification.

Tuning catalysis of boronic acids in microgels by in situ reversible structural variations.

The catalysis of boronic acids immobilized in polymer microgels can be modulated by bubbling with N2/CO2 gas, and in some cases by adding glucose, making their catalytic activity comparable or even superior to that of the corresponding free boronic acid monomers homogeneously dispersed in solutions and, more importantly, making these boronic-acid-containing polymer microgels able to catalyze alternate reactions that may extend the usefulness. This enhanced catalytic function of these boronic-acid-containing microgels as organoboron acid catalysts is plausibly achieved via in situ reversibly structural variations. Kinetic studies have been carried out on the model boronic-acid-catalyzed aza-Michael addition, aldol, amidation, and [4 + 2] cycloaddition reactions in order to better understand the catalytic process.

One-pot HTST synthesis of responsive fluorescent ZnO@apo-enzyme composite microgels for intracellular glucometry.

Responsive fluorescent microgels, that can selectively, reversibly, and rapidly convert the fluctuation in intracellular glucose level into fluorescence signal, have the potential use for intracellular glucometry to promote the understanding of physiology. Herein, we report one-pot synthesis of such a responsive fluorescent composite microgels, which is made of a representative apo-enzyme, apo-glucose oxidase (apo-GOx), interpenetrated in a composite gel network that is comprised of ZnO quantum dots covalently bonded onto crosslinked poly(ethylene glycol) dimethacrylate. The key of this one-pot synthesis is applying a high-temperature short-time heating (HTST) method, so that the naturally dynamic profile of apo-GOx can be maintained and harnessed on the composite microgels to allow the highly selective response to glucose over a glucose concentration range of 0-20 mM. While the composite microgels can undergo volume phase transitions and convert both an increase and a decrease in glucose concentration into fluorescence signal shortly (<1 s), the changes in average hydrodynamic diameter and fluorescence of the composite microgels can be fully reversible even after twenty cycles of adding/removing glucose, indicating a reversible and rapid time response to the glucose concentration variations. With the composite microgels as biosensors, the fluorescence of the composite microgels embedded in the model cancer cells B16F10 can be modulated in response to intracellular glucose level variations, which are derived from a change in glucose concentration in the culture medium by an external supply, or that can be triggered by biochemical reactions (with the ß-galactosidase catalysed hydrolysis of lactose as a model reaction for achieving increased glucose levels, and the GOx catalysed oxidation of glucose for achieving decreased glucose levels).

Salt-Enhanced CO2-Responsiveness of Microgels.

Here, we report a distinct mechanism for harnessing CO2-responsiveness through enhancing CO2 capture ability. The finding is demonstrated on the microgels that are composed of oligo(ethylene glycol) and sulfonate moieties. Laser light scattering studies on dilute aqueous dispersion of these microgels indicated a low CO2-responsivity, which can be significantly enhanced by adding NaCl and other salts. This salt-enhanced CO2-responsiveness of microgels can be elucidated by the antipolyelectrolyte behavior and its superposition of forming cross-links physically with CO2 as an intermediate. Further results of the filtration experiments on microgel translocation through pores suggest the feasibility of the explanation. The finding is also supported by the CO2 capture-release experiments on the dispersion, which can reversibly absorb and desorb CO2.

Observation of Unusual Thermoresponsive Volume Phase Transition Behavior of Cubic Poly(N-isopropylacrylamide) Microgels.

Here, we report the observation of an unusual thermoresponsive volume phase transition behavior of cubic poly(N-isopropylacrylamide) (PNIPAM) microgels. Cubic PNIPAM microgels with a mean edge size of 125 ± 41 nm were synthesized via electrochemical-initiated radical polymerization with a photovoltaic cell as power supply. In turbidity and laser light scattering studies on dilute aqueous dispersions of these cubic microgels, both the light attenuation and hydrodynamic radius variations with temperature reveal an additional transition at about 25.0 °C, besides the widely reported volume phase transition at the PNIPAM LCST that is typically found for (quasi-)spherical microgels. This unusual thermoresponsive volume phase transition behavior of the cubic microgels can be elucidated by using a core-corona model, with the contribution from each part varying at different temperatures. The finding is also checked by thermal analysis.

Facile synthesis of silver nanoparticles in a crosslinked polymeric system by in situ reduction method for catalytic reduction of 4-nitroaniline.

In this study, poly(N-isopropylmethacrylamide-co-methacrylic acid) microgels prepared by free radical precipitation polymerization were used as micro-reactors for the synthesis and stabilization of silver nanoparticles. UV-Visible spectroscopy, Transmission Electron Microscopy and Fourier-transform infrared spectroscopy were used to characterize both pure and hybrid microgels. The catalytic reduction of 4-nitroaniline was carried out in the presence of hybrid microgels to test their catalytic activity, and the catalysis mechanism was explored by varying the concentrations of reacting species like 4-nitroaniline and NaBH4, as well as the dose of the catalyst. The kinetic data indicates that this reaction follows pseudo-first order. The variation in apparent rate constant (kapp) with respect to NaBH4 concentration also discloses it to be the following Langmuir-Hinshelwood mechanism. The relationship between catalyst concentration and apparent rate constant was found to be increasing in a linear manner. The data obtained also confirmed that silver nanoparticles loaded microgels have the potential to be used as an excellent micro-reactor for selective reduction of 4-nitroaniline to p-phenylenediamine.

Engineering of responsive polymer based nano-reactors for facile mass transport and enhanced catalytic degradation of 4-nitrophenol.

Silver nanoparticles with average diameter of 10±3nm were synthesized within the sieves of poly(N-isopropylacrylamide-2-hydroxyethylmethacrylate-acrylic acid) (p(NIPAAm-HEMA-AAc)) polymer microgels. Free radial emulsion polymerization was employed for synthesis of p(NIPAAm-HEMA-AAc) polymer microgels. Silver nanoparticles were introduced within the microgels sphere by in situ reduction method. Microgels and hybrid microgels were characterized by Fourier transform infrared spectroscopy, ultra violet-visible spectroscopy, transmission electron microscopy and dynamic light scattering measurements. Catalytic activity of Ag-p(NIPAAm-HEMA-AAc) hybrid microgels was studied using catalytic reduction of 4-nitrophenol (4-NP) as a model reaction in aqueous media. The influence of sodium borohydride (NaBH4) concentration, catalyst dose and 4-NP concentration on catalytic reduction of 4-NP was investigated. A linear relationship was found between catalyst dose and apparent rate constant (kapp). The mechanism of catalysis by hybrid microgels was explored for further development in this area. The deep analysis of catalytic process reveals that the unique combination of NIPAAm, HEMA and AAc does not only stabilize silver nanoparticles in polymer network but it also enhances the mass transport of hydrophilic substrate like 4-NP from outside to inside the polymer network.

Immobilization of sulfur in microgels for lithium-sulfur battery.

Immobilization of sulfur in microgels is achieved via free radical polymerization of commercial poly(ethylene glycol) dimethacrylate in the solution of sulfur-terminated poly(3-oligo(ethylene oxide)4-thiophene), a copolymer prepared by the inverse vulcanization of S8 with allyl-terminated poly(3-oligo(ethylene oxide)4-thiophene). This microgelation leads to enhanced Li-S battery performance over the sulfur-terminated polymer.

Glucose-mediated catalysis of Au nanoparticles in microgels.

The catalytic activity of Au nanoparticles in phenylboronic acid-containing polymer microgels can be tuned through the swelling-deswelling transition of the microgels in response to changes in glucose concentration. Upon adding glucose, the model catalytic reduction of hydrophilic 4-nitrophenol is accelerated, while the reduction of relatively more hydrophobic nitrobenzene slows down.

Enhanced enzymatic hydrolysis of cellulose in microgels.

A cellulose-based microgel, where an individual microgel contains approximately one cellulose chain on average, is synthesized via free radical polymerization of a difunctional small-molecule N,N'-methylenebisacrylamide in cellulose solution. This microgelation leads to a low-ordered cellulose, favoring enzymatic hydrolysis of cellulose to generate glucose.

Copper on responsive polymer microgels: a recyclable catalyst exhibiting tunable catalytic activity.

Copper has been immobilized on a chitosan-based responsive polymer microgel by simply stirring the microgel dispersion with copper sulfate. The ensuing catalyst is highly active for a model azide-alkyne [3+2]-cycloaddition reaction, and can be recycled at least 5 times; the catalytic activity can be tuned via swelling-deswelling transitions of the polymer gels.

[Development of a droplet-interfaced high performance liquid chromatography-capillary electrophoresis two dimensional separation platform].

Proteomics demands high resolution multidimensional separation techniques due to its extremely high complexity. Droplet microfluidics provides a series of unique advantages in manipulating micro and nanolitre samples, such as micro-volume operation, limited diffusion and none cross-contaminating, therefore has the potential to be an ideal interface strategy for multidimensional separation. Using the microchips of different structures, functions such as "droplet generation" and "oil depletion" can be realized. Based on these functions, samples can be transferred from continuous flow to segmented flow and then back to continuous flow. In this way, different separation modes can be combined. In this study, droplet technology was utilized as a novel interface strategy in combining high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Using tryptic peptides mixture as a sample, this two dimensional HPLC-CE system provided high resolution separation with a peak capacity over 3000. This proof-of-principle study has demonstrated the usefulness of droplet interface technology in multidimensional separation.