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.

A facile and efficient method of enzyme immobilization on silica particles via Michael acceptor film coatings: immobilized catalase in a plug flow reactor.

A novel method was developed for facile immobilization of enzymes on silica surfaces. Herein, we describe a single-step strategy for generating of reactive double bonds capable of Michael addition on the surfaces of silica particles. This method was based on reactive thin film generation on the surfaces by heating of impregnated self-curable polymer, alpha-morpholine substituted poly(vinyl methyl ketone) p(VMK). The generated double bonds were demonstrated to be an efficient way for rapid incorporation of enzymes via Michael addition. Catalase was used as model enzyme in order to test the effect of immobilization methodology by the reactive film surface through Michael addition reaction. Finally, a plug flow type immobilized enzyme reactor was employed to estimate decomposition rate of hydrogen peroxide. The highly stable enzyme reactor could operate continuously for 120 h at 30 °C with only a loss of about 36 % of its initial activity.

Determination of mercury(II) in the presence of methylmercury after preconcentration using poly(acrylamide) grafted onto cross-linked poly(4-vinyl pyridine): application to mercury speciation.

The applicability of poly(acrylamide) grafted onto cross-linked poly(4-vinyl pyridine) (P4-VP-g-PAm) has been investigated for the separation, preconcentration and speciation of Hg(II) and MeHg(I). In batch experiments, Hg(II) was quantitatively retained (≥95%) in the pH range of 1.0-8.0, whereas the sorption of MeHg(I) was insignificant in the pH range of 1.0-2.0. Freundlich and Langmuir isotherm models were investigated in order to characterize the sorption, and the capacity of the sorbent was found to be 817 mg Hg(II) g(-1). The limit of detection (3δ above blank) was 2 ng L(-1). The sorbent has excellent selectivity for Hg(II) in the presence of Pb(II), Zn(II), Cu(II), Cd(II) and Fe(III) ions. The method was successfully applied to the determination of Hg(II) and MeHg(I) in seawater and estuarine water. The sorbent can remove Hg(II) at pH 2.0, and therefore makes the determination of MeHg(I) possible, even if the sample contains a high amount of Hg(II).

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.