Application of aza-BODIPY as a Nitroaromatic Sensor.

Nitroaromatic explosive detection with high sensitivity and selectivity is requisite for civilian and military safety and the ecosystem. In this study, aza boron dipyrromethene (aza-BODIPY) dye was selected as a fluorescent-based chemosensor against nitroaromatic compounds (NACs) including 2,4,6-trinitrophenol (picric acid, TNP), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT). This dye molecule exhibits sharp fluorescent behavior with high quantum yields beyond the near-infrared region (NIR) and is considered as a potential candidate for the detection of NACs. O'Shea's approach was used to synthesize tetraphenyl-conjugated aza-BODIPY molecules. Quenching of fluorescence emission of aza-BODIPY at 668 nm after the exposure to NACs was investigated under acetonitrile-water and acetonitrile-ethanol solvent conditions. The quenching responses and its mechanism were examined by considering the Stern-Volmer relationship Stern-Volmer constants (Ksv) for TNP (in water), TNP (in ethanol), TNT, and DNT, which are predicted to be 1420, 1215, 1364, and 968 M-1, respectively, all of which are sufficiently above the limit of detection (LOD) values. Thus, the present study opens up the possibility of the usage of aza-BODIPY molecules as a low-cost, light-weight sensor for the detection of NAC explosives.

Synthesis of Core-Shell Polyborosiloxanes as a Heat-Resistant Platform.

Herein, new polyborosiloxanes (PBSs) were prepared using a straightforward synthetic approach to obtain a core-shell structure as a material with various features such as better adhesion ability to the applied surface and enhanced thermal properties. In this concept, in situ core-shell formation was allowed by sequential addition of ingredients with fixed conversions. First, pre-condensed polysiloxane was synthesized, with a 60% conversion, as a core by the reaction of phenyltriethoxysilane in the presence of water in an acidic condition. Subsequent addition of boric acid into the pre-condensate and a further condensation reaction resulted in the formation of the shell layer through the introduction of the -Si-O-B- bonds to the network of the PBS. The resulting resin was used as a binder for heat-resistant paint in combination with an aluminum pigment, and the paint applied on a metal plate was found to be resistant up to 600 °C in terms of adhesion strength. It was also demonstrated that the incorporation of boron in the core-shell structure showed better adhesion strength than the one-pot preparation of PBS. Using this method, not only the heat resistance requirement of the industrial coating was achieved but also the flame-retardant ability was introduced.

Polystyrene-divinyl benzene microspheres with amino methyl phosphonic acid functional hairy brushes for the sorption and speciation of chromium prior to inductively coupled plasma mass spectrometric determination.

This article describes the synthesis and application of a novel sorbent for Cr(III) and Cr(VI) speciation prior to their quantitation by inductively coupled plasma mass spectrometry. The sorbent consists of polystyrene-divinyl benzene microbeads that were graft-coated with poly(oligo (ethylene glycol) methacrylate)-block-poly(glycidyl methacrylate). The particles were finally modified with phosphomethylated triethylene tetramine. The resulting microbeads are shown to be a viable sorbent for Cr(VI). The total concentration of chromium was determined after oxidation of Cr(III) to Cr(VI) with KMnO4 using the novel sorbent. The Cr(III) amount was then calculated by subtracting the concentration of Cr(VI) from that of total chromium. The optimum conditions for batch type sorption were established. Under optimal conditions, the limit of detection and quantification are 0.015 µg L-1 and 0.050 µg L-1, respectively. The kinetics and isotherms of the sorption of Cr(VI) were investigated. Following desorption with 0.1 M hydroxylamine hydrochloride, the method was successfully applied to spiked real water samples and a certified reference material. Graphical abstract Schematic presentation of a method for the sorption and speciation of chromium using amino methyl phosphonic acid functional brushes on polystyrene-divinyl benzene microspheres.

Highly fluorescent sensing of nitroaromatic explosives in aqueous media using pyrene-linked PBEMA microspheres.

Crosslinked 2-bromoethyl methacrylate polymer (PBEMA) was prepared in micro-spherical form (2-5µm) by precipitation polymerization methodology. The bromide substituent was substituted with an azide group, which was then coupled with 1-[(2-Propynyloxy)methyl]pyrene] via alkyne-azide click chemistry. The pyrene-linked microspheres showed an intense green-blue excimer emission with a maximum at 480nm, implying π-π stacking between the pyrene moieties on the microsphere surfaces. This fluorescence emission is extremely sensitive to the aromatic nitro compounds. So that the green-blue light fades immediately upon addition of trace amounts of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitro phenol (TNP) in 100% aqueous media. Stern-Volmer plots were employed for comparison of their fluorescence quenching effects. The plots revealed Stern-Volmer constants of 1.33 × 105, 2.451 × 105 and 1.076 × 105M-1 for TNT, TNP and DNT, respectively. Furthermore, it has been observed that, the microspheres can be reused several times, without losing excimer emission properties.

Pair correlation microscopy reveals the role of nanoparticle shape in intracellular transport and site of drug release.

Nanoparticle size, surface charge and material composition are known to affect the uptake of nanoparticles by cells. However, whether nanoparticle shape affects transport across various barriers inside the cell remains unclear. Here we used pair correlation microscopy to show that polymeric nanoparticles with different shapes but identical surface chemistries moved across the various cellular barriers at different rates, ultimately defining the site of drug release. We measured how micelles, vesicles, rods and worms entered the cell and whether they escaped from the endosomal system and had access to the nucleus via the nuclear pore complex. Rods and worms, but not micelles and vesicles, entered the nucleus by passive diffusion. Improving nuclear access, for example with a nuclear localization signal, resulted in more doxorubicin release inside the nucleus and correlated with greater cytotoxicity. Our results therefore demonstrate that drug delivery across the major cellular barrier, the nuclear envelope, is important for doxorubicin efficiency and can be achieved with appropriately shaped nanoparticles.

An efficient and highly versatile synthetic route to prepare iron oxide nanoparticles/nanocomposites with tunable morphologies.

We report a versatile synthetic method for the in situ self-assembly of magnetic-nanoparticle-functionalized polymeric nanomorphologies, including spherical micelles and rod-like and worm-like micelles and vesicles. Poly(oligoethylene glycol methacrylate)-block-(methacrylic acid)-block-poly(styrene) (POEGMA-b-PMAA-b-PST) triblock copolymer chains were simultaneously propagated and self-assembled via a polymerization-induced self-assembly (PISA) approach. Subsequently, the carboxylic acid groups in the copolymers were used to complex an iron ion (Fe(II)/Fe(III)) mixture. Iron oxide nanoparticles were then formed in the central block, within the polymeric nanoparticles, via alkaline coprecipitation of the iron(II) and (III) salts. Nanoparticle morphologies, particle sizes, molecular weights, and chemical structures were then characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), size exclusion chromatography (SEC), and (1)H NMR measurements. TEM micrographs showed that the average size of the magnetic nanoparticles was ∼7 nm at the hydrophobic/hydrophilic nexus contained within the nanoparticles. In addition, XRD was used to confirm the formation of iron oxide nanoparticles. Importantly, the polymeric nanoparticle morphologies were not affected by the coprecipitation of the magnetic nanoparticles. The hybrid nanoparticles were then evaluated as negative MRI contrast agents, displaying remarkably high transverse relaxivities (r2, greater than 550 mM(-1) s(-1) at 9.4 T); a result, that we hypothesize, ensues from iron oxide nanoparticle clustering at the hydrophobic-hydrophilic interface. This simple synthetic procedure is highly versatile and produces nanocarriers of tunable size and shape with high efficacy as MRI contrast agents and potential utility as theranostic delivery vectors.

Simultaneous polymerization-induced self-assembly (PISA) and guest molecule encapsulation.

Nanoparticles with various morphologies such as micelles, worm-like/rod-like and spherical vesicles are made using a polymerization-induced self-assembly (PISA) approach via a one-pot RAFT dispersion polymerization. On polymerization/self-assembly, we report a concurrent highly efficient loading of guest molecules within the nanoparticle structures. Different nanoparticle morphologies, such as spherical micelles, worm-like, rod-like, and spherical vesicles, are achieved by gradually increasing the number-average degree of polymerization (DPn) of the PST block via increasing polymerization times (in a poor solvent) as determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. In parallel, a guest molecule (Nile Red) is encapsulated during the polymerization without disturbing the morphology or the polymerization kinetics.

In Situ Formation of Polymer-Gold Composite Nanoparticles with Tunable Morphologies.

A simple and efficient route to gold-polymer nanoparticle composites is described. Our versatile synthetic route exerts facile control over polymer nanoparticle morphology, including micelles, rod-like structures, and vesicles, all easily attainable from a single polymerization taken to different monomer conversions. Specifically, poly[oligo(ethylene glycol) methacrylate]-b-poly(dimethylaminoethyl methacrylate)-b-poly(styrene) (POEGMA-b-PDMAEMA-b-PST) triblock copolymers were synthesized using a polymerization induced self-assembly (PISA) approach. Subsequently, spherical gold nanoparticles (10 nm AuNPs) were formed at the hydrophilic-hydrophobic nexus of the assembled triblock copolymer nanoaggregates by the addition of chloroauric acid (HAuCl4) followed by in situ reduction using NaBH4. After reduction, the cloudy white nanoparticle dispersions turned to a red-purple color. The gold nanoparticles that formed were stabilized by the enveloping polymeric nanostructures, neither precipitation nor agglomeration occurred. We demonstrated that we were able to tune the gold nanoparticle composition in these polymer-gold composites by varying the concentration of chloroauric acid. Morphology, particle size, molecular weight, AuNP content, and chemical structure of the polymer structures were characterized by transmittance electron microscopy (TEM), dynamic light scattering (DLS), size exclusion chromatography (SEC), thermal gravimetric analysis (TGA), and 1H NMR. Finally, the formation of the AuNPs occurred without affecting the polymer nanoparticle morphology.

Amine functional monodisperse microbeads via precipitation polymerization of N-vinyl formamide: immobilized laccase for benzidine based dyes degradation.

Densely cross-linked poly(vinylamine) microbeads (∼ 2 µm) were prepared by precipitation copolymerization of N-vinyl formamide and ethylene glycoldimethacrylate in acetonitrile. The formamido groups of the microbeads were hydrolyzed into amino groups. Then, amino-functionalized microbeads were used for covalent immobilization of laccase via glutaraldehyde coupling. The average amount of immobilized enzyme was 18.7 mg/g microbeads. Kinetic parameters, V(max) and K(m) values were determined as 20.7 U/mg protein and 2.76 × 10(-2)mmol/L for free enzyme and 15.8 U/mg protein and 4.65 mmol/L for the immobilized laccase, respectively. The immobilized laccase was operated in a batch reactor for the degradation of two different benzidine based dyes (i.e., Direct Blue 1 and Direct Red 128). The laccase immobilized on the microbeads was very effective for removal of these dyes which interfere with the hormonal system.

Poly(styrene-divinylbenzene) beads surface functionalized with di-block polymer grafting and multi-modal ligand attachment: performance of reversibly immobilized lipase in ester synthesis.

Fibrous poly(styrene-b-glycidylmethacrylate) brushes were grafted on poly(styrene-divinylbenzene) (P(S-DVB)) beads using surface-initiated atom transfer radical polymerization. Tetraethyldiethylenetriamine (TEDETA) ligand was incorporated on P(GMA) block. The ligand attached beads were used for reversible immobilization of lipase. The influences of pH, ionic strength, and initial lipase concentration on the immobilization capacities of the beads have been investigated. Lipase adsorption capacity of the beads was about 78.1 mg/g beads at pH 6.0. The Km value for immobilized lipase was about 2.1-fold higher than that of free enzyme. The thermal, and storage stability of the immobilized lipase also was increased compared to the native lipase. It was observed that the same support enzyme could be repeatedly used for immobilization of lipase after regeneration without significant loss in adsorption capacity or enzyme activity. A lipase from Mucor miehei immobilized on styrene-divinylbenzene copolymer was used to catalyze the direct esterification of butyl alcohol and butyric acid.

Immobilization of catalase via adsorption on poly(styrene-d-glycidylmethacrylate) grafted and tetraethyldiethylenetriamine ligand attached microbeads.

Fibrous poly(styrene-d-glycidylmethacrylate) (P(S-GMA)) brushes were grafted on poly(styrene-divinylbenzene) (P(S-DVB)) beads using surface initiated-atom transfer radical polymerization (SI-ATRP). Tetraethyldiethylenetriamine (TEDETA) ligand was incorporated on P(GMA) block. The multi-modal ligand attached beads were used for reversible immobilization of catalase. The influences of pH, ionic strength and initial catalase concentration on the immobilization capacities of the P(S-DVB)-g-P(S-GMA)-TEDETA beads have been investigated. Catalase adsorption capacity of P(S-DVB-g-P(S-GMA)-TEDETA beads was found to be 40.8 ± 1.7 mg/g beads at pH 6.5 (with an initial catalase concentration 1.0mg/mL). The K(m) value for immobilized catalase on the P(S-DVB-g-P(S-GMA)-TEDETA beads (0.43 ± 0.02 mM) was found about 1.7-fold higher than that of free enzyme (0.25 ± 0.03 mM). Optimum operational temperature and pH was increased upon immobilization. The same support was repeatedly used five times for immobilization of catalase after regeneration without significant loss in adsorption capacity or enzyme activity.

Modification of polydivinylbenzene microspheres by a hydrobromination/click-chemistry protocol and their protein-adsorption properties.

Hydrophobic- and/or hydrophilic-polymer-grafted PDVB microspheres are synthesized by the combination of hydrobromination and click-chemistry processes. The modified-PDVB microspheres and the intermediates at various stages of synthesis are characterized using GPC, ¹H NMR and FTIR spectroscopy and TGA analysis. Use of the microspheres as a support matrix for reversible protein immobilization via adsorption is investigated. The system parameters such as the adsorption conditions (i.e., enzyme concentration, medium pH) and desorption are studied and evaluated with regards to the biocatalytic activity and adsorption capacity.