Binary Polymer Brushes on Silica@Polymer Hybrid Nanospheres and Hollow Polymer Nanospheres by Combined Alkyne−Azide and Thiol−Ene Surface Click Reactions

Green Synthesis of Hollow Structures through the Decomposition of Azo Compounds Incorporated inside Polystyrene Particles

Hollow polymer particles are applied in various fields owing to their high specific surface area and inner volume. The hollow regions in such particles are generally synthesized using a template. However, chemical agents must be used to remove the templates, which is associated with a high environmental load. To address this problem, we previously established a method for synthesizing hollow polymer particles without a template. However, the mechanism underlying this synthesis was unclear, which this study aimed to rectify. First, azo compounds were dissolved in a styrene monomer phase, and soap-free emulsion polymerization was performed to produce polystyrene particles. The azo compounds were incorporated into the polystyrene particles from the monomer phase at a polymerization temperature greater than the melting point of the azo compounds. Finally, the polystyrene particles were heated at a temperature greater than the 10 h half-life temperature of the azo compounds to emit nitrogen gas, and the azo compounds were decomposed to prepare the hollow regions in the polystyrene particles. However, the resulting particles were not hollow when the azo compound was not incorporated into the polystyrene particles. By comparing the melting behavior of different azo compounds, this study elucidates the mechanism underlying our template-free method for synthesizing hollow polystyrene particles.

Copolymerization of Mesoporous Styrene-Bridged Organosilica Nanoparticles with Functional Monomers for the Stimuli-Responsive Remediation of Water

For every mass product, there are problems associated with the resulting waste. Residues of hormones in urine cannot be removed sufficiently from wastewater, and this has undesired consequences. An ideal adsorbent would take up the impurity, enable a simple separation and recyclability. Polymer colloids with high affinity towards the drug, accessible porosity, high surface area, and stimuli-responsive properties would be candidates, but such a complex system does not exist. Here, porous vinyl-functionalized organosilica nanoparticles prepared from a styrene bridged sol-gel precursor act as monomers. Initiation of the polymerization at the pore walls and addition of functional monomers result in a special copolymer, which is covalently linked to the surface and covers it. An orthogonal modification of external surface was done by click attachment of a thermoresponsive polymer. The final core-shell system is able to remove quantitatively hydrophobic molecules such as the hormone progesterone from water. A change of temperature closes the pores and induces the aggregation of the particles. After separation one can reopen the particles and recycle them.

Combining Click Reactions for the One-Pot Synthesis of Modular Biomolecule Mimetics

Here, we report on the first combined one-pot use of the two so-called "click reactions": the thiol-ene coupling and the copper-catalyzed alkyne-azide cycloaddition. These reactions were employed in an alternating and one-pot fashion to combine appropriately functionalized monomeric carbohydrate building blocks to create mimics of trisaccharides and tetrasaccharides as single anomers, with only minimal purification necessary. The deprotected oligosaccharide mimics were found to bind both plant lectins and human galectin-3.

Preparation of Colloidally Stable Positively Charged Hollow Silica Nanoparticles: Effect of Minimizing Hydrolysis on ζ Potentials

Silica nanoparticles have received great attention as versatile nanomaterials in many fields such as drug delivery, sensing, and imaging due to their physical and chemical flexibility. Specifically, the silanol groups at the surface of silica nanoparticles have enabled various surface modifications and functionalization to tailor the nanoparticles for each application. Chemical tailoring to switch from negative to positive surface charge has been one important strategy to enhance cell internalization and biodistribution of the nanoparticles. However, efficient surface charge modification that is sustained upon dispersion is difficult to achieve and has not been well characterized though it can be a critical requirement for successful nanoparticle performance. In this study, solid spherical silica nanoparticles and hollow spherical silica nanoparticles around 45 nm in diameter were synthesized, both possessing tunable positive ζ potentials in aqueous colloidal suspension, to investigate the relationship between time-dependent ζ potential changes and their morphologies. A set of three different particles showing varied ζ potentials of approximately 5, 20, and >30 mV in both morphologies were prepared, and their colloidal surface electric potential fluctuations were measured. These studies reveal that the hollow morphologies are much more effectively able to maintain positive ζ potentials for 7 days of aqueous incubation, whereas the magnitude of the ζ potential of the solid silica spheres decreases uncontrollably, largely due to hydrolysis of the interior siloxane bonds, resulting in adsorption of the released silicic acid onto the nanoparticle surface.

A label-free immunosensor based on PHEMA/graphene oxide nanocomposite for simultaneous electrochemical determination of alpha fetoprotein

An electrochemical immunosensor based on poly(2-hydroxyethyl methacrylate) (PHEMA)/graphene oxide (GO) nanocomposite was designed in a simple way for the ultrasensitive detection of tumor makers (alpha-fetoprotein, AFP as a model). PHEMA with excellent biocompatibility, provides a large number of sites for connecting signal molecules. After modification with signal molecules, the functional PHEMA significantly improved the sensitivity of electrochemical detection. In order to immobilize antibodies, GO was introduced and used to construct a nanocomposite as a substrate. The designed AFP immunosensor showed favorable selectivity and excellent stability. Meanwhile, it has a low detection limit of 0.403 pg mL-1. Furthermore, the immunosensor was used to detect target AFP in human serum, demonstrating the feasibility of clinical diagnosis.

Preparation and unique dielectric properties of nanoporous materials with well-controlled closed-nanopores

Although general porous materials have a low dielectric constant, their uncontrollable opened porous structure results in high dielectric loss and poor barrier properties, thus limiting their application as interconnect dielectrics.

Magnetic Fe3O4 nanoparticles supporting Macmillan with controlled shell structure as an efficient and reusable catalyst for asymmetric reaction

Magnetic nanoparticles grafted with chiral polymer brushes offer an effective way to bridge the gap between heterogeneous and homogeneous catalysis.

Tailor-Made Boronic Acid Functionalized Magnetic Nanoparticles with a Tunable Polymer Shell-Assisted for the Selective Enrichment of Glycoproteins/Glycopeptides

Biomedical sciences, and in particular biomarker research, demand efficient glycoproteins enrichment platforms. In this work, we present a facile and time-saving method to synthesize phenylboronic acid and copolymer multifunctionalized magnetic nanoparticles (NPs) using a distillation-precipitation polymerization (DPP) technique. The polymer shell is obtained through copolymerization of two monomers-affinity ligand 3-acrylaminophenylboronic acid (AAPBA) and a hydrophilic functional monomer. The resulting hydrophilic Fe3O4@P(AAPBA-co-monomer) NPs exhibit an enhanced binding capacity toward glycoproteins by an additional functional monomer complementary to the surface presentation of the target protein. The effects of monomer ratio of AAPBA to hydrophilic comonomers on the binding of glycoproteins are systematically investigated. The morphology, structure, and composition of all the synthesized microspheres are characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The hydrophilic Fe3O4@P(AAPBA-co-monomer) microspheres show an excellent performance in the separation of glycoproteins with high binding capacity; And strong magnetic response allows them to be easily separated from solution in the presence of an external magnetic field. Moreover, both synthetic Fe3O4@P(AAPBA) and copolymeric NPs show good adsorption to glycoproteins in physiological conditions (pH 7.4). The Fe3O4@P(AAPBA-co-monomer) NPs are successfully utilized to selectively capture and identify the low-abundance glycopeptides from the tryptic digest of horseradish peroxidase (HRP). In addition, the selective isolation and enrichment of glycoproteins from the egg white samples at physiological condition is obtained by Fe3O4@P(AAPBA-co-monomer) NPs as adsorbents.

Thiol–isocyanate click reaction in a Pickering emulsion: a rapid and efficient route to encapsulation of healing agents

An innovative, rapid and efficient route is developed to fabricate ene loaded microcapsules via a thiol–isocyanate click reaction based on a hydrolyzed poly(glycidyl methacrylate) (PGMA) particle stabilized oil-in-water Pickering emulsion.

Monofunctional polymer nanoparticles prepared through intramolecularly cross-linking the polymer chains sparsely grafted on the surface of sacrificial silica spheres

Polymeric monofunctional nanoparticles with exactly one functional group on the surface of each nanoparticle are prepared.

Synthesis and characterization of silica nanoparticles functionalized with multiple TEMPO groups and investigation on their oxidation activity

A series of novel silica nanoparticles functionalized with multiple TEMPO groups were synthesized using a novel, efficient and versatile protocol, and the catalytic activity of SN-g-(PGMA-TEMPO) was evaluated by the oxidation of benzylic alcohols.

Synthesis of mixed poly(ε-caprolactone)/polystyrene brushes from Y-initiator-functionalized silica particles by surface-initiated ring-opening polymerization and nitroxide-mediated radical polymerization

This article reports the synthesis of mixed brushes by ring-opening polymerization of ε-caprolactone and nitroxide-mediated radical polymerization of styrene from Y-initiator-functionalized silica particles.

Thiol–ene “click” reactions and recent applications in polymer and materials synthesis: a first update

This contribution serves as an update to a previous review (Polym. Chem.2010,1, 17–36) and highlights recent applications of thiol–ene ‘click’ chemistry as an efficient tool for both polymer/materials synthesis as well as modification.

A Solid-State NMR Investigation of MQ Silicone Copolymers

The structure of MQ copolymers of the general chemical formula [(CH₃)₃SiO_0.5]_m [SiO₂]_n was characterized by means of solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The MQ copolymers are highly branched polycyclic compounds (densely cross-linked nanosized networks). MQ copolymers were prepared by hydrolytic polycondensation in active medium. ²⁹Si NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) ²⁹Si{¹H} techniques in concert with MAS. It was shown that material consist of monofunctional M (≡SiO Si (CH₃)₃) and two types of tetrafunctional Q units: Q⁴ ((≡SiO)₄Si) and Q³ ((≡SiO)₃SiOH). Spin-lattice relaxation times T₁ measurements of ²⁹Si nuclei and analysis of ²⁹Si{¹H} variable contact time signal intensities allowed us to obtain quantitative data on the relative content of different sites in copolymers. These investigations indicate that MQ copolymers represent dense structure with core and shell.

Surface modification of silicone for biomedical applications requiring long-term antibacterial, antifouling, and hemocompatible properties

Silicone has been used for peritoneal dialysis (PD) catheters for several decades. However, bacteria, platelets, proteins, and other biomolecules tend to adhere to its hydrophobic surface, which may lead to PD outflow failure, serious infection, or even death. In this work, a cross-linked poly(poly(ethylene glycol) dimethacrylate) (P(PEGDMA)) polymer layer was covalently grafted on medical-grade silicone surface to improve its antibacterial and antifouling properties. The P(PEGDMA)-grafted silicone (Silicone-g-P(PEGDMA)) substrate reduced the adhesion of Staphylococcus aureus , Escherichia coli , and Staphylococcus epidermidis , as well as 3T3 fibroblast cells by ≥90%. The antibacterial and antifouling properties were preserved after the modified substrate was aged for 30 days in phosphate buffer saline. Further immobilization of a polysulfobetaine polymer, poly((2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide) (P(DMAPS)), on the Silicone-g-P(PEGDMA) substrate via thiol-ene click reaction leads to enhanced antifouling efficacy and improved hemocompatibility with the preservation of the antibacterial property. Compared to pristine silicone, the so-obtained Silicone-g-P(PEGDMA)-P(DMAPS) substrate reduced the absorption of bovine serum albumin and bovine plasma fibrinogen by ≥80%. It also reduced the number of adherent platelets by ≥90% and significantly prolonged plasma recalcification time. The results indicate that surface grafting with P(PEGDMA) and P(DMAPS) can be potentially useful for the modification of silicone-based PD catheters for long-term applications.

Surface functionalization of barium titanate SHG nanoprobes for in vivo imaging in zebrafish

To address the need for a bright, photostable labeling tool that allows long-term in vivo imaging in whole organisms, we recently introduced second harmonic generating (SHG) nanoprobes. Here we present a protocol for the preparation and use of a particular SHG nanoprobe label, barium titanate (BT), for in vivo imaging in living zebrafish embryos. Chemical treatment of the BT nanoparticles results in surface coating with amine-terminal groups, which act as a platform for a variety of chemical modifications for biological applications. Here we describe cross-linking of BT to a biotin-linked moiety using click chemistry methods and coating of BT with nonreactive poly(ethylene glycol) (PEG). We also provide details for injecting PEG-coated SHG nanoprobes into zygote-stage zebrafish embryos, and in vivo imaging of SHG nanoprobes during gastrulation and segmentation. Implementing the PROCEDURE requires a basic understanding of laser-scanning microscopy, experience with handling zebrafish embryos and chemistry laboratory experience. Functionalization of the SHG nanoprobes takes ∼3 d, whereas zebrafish preparation, injection and imaging setup should take approximately 2-4 h.

Elastic properties of a protein-polymer-grafted surface

Surfaces grafted with poly(methyl methacrylate) (PMMA) and streptavidin were synthesized through click chemistry to investigate the role of surface stiffness on protein adsorption as the hydrophilic and hydrophobic surface coverage of the substituents vary. Surface topographies coupled with the nanoindentation results indicated that, with the appropriate selections of polymer coverage and chain length, the extent of non-specific protein adhesion could be controlled by the hydrophobic interactions between PMMA, biotin, and streptavidin. It was shown that, when the molecular weight and stiffness of PMMA was close to that of streptavidin, patchy PMMA morphologies were obtained, which help inhibit the non-specific adsorption of streptavidin.

Synthesis and characterization of silica nanoparticles with well-defined thermoresponsive PNIPAM via a combination of RAFT and click chemistry

Covalent functionalization of azide-modified SiO(2) with well-defined, alkyne-terminated poly(N-isopropylacrylamide) was accomplished by the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition. The alkyne-terminated RAFT chain transfer agent was first synthesized, and then the alkyne-terminated thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) with different molecular weights were synthesized by the RAFT of NIPAM monomer. The polymerization kinetics and the evolution of number-average molecular weights (M(n)), and polydispersities (M(w)/M(n)), with monomer conversions were investigated. A copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "grafting to" method was used to attach thermoresponsive polymers onto the exterior surface of SiO(2) nanoparticles which produced relatively high grafting density. The as-synthesized hybrid nanoparticles showed thermoresponsive behavior and were characterized by FTIR, XPS, TGA, DLS, and TEM, etc.