These acrylic microspheres were hydrophobic in character with a

These acrylic microspheres were hydrophobic in character with a surface modified acryloxysuccinimide functionality (poly-nBA-NAS) for the immobilization of the enzyme. They were synthesized via photopolymerization. As the microspheres are hydrophobic, the AOX immobilization will be confined to the surface of the spheres, thus allowing the enzymatic reaction of AOX and formaldehyde to occur at the surface. With a large surface area of the microsphere to be use as a potetiometric biosensor membrane and favorable surface diffusion conditions, the analytical performance of the formaldehyde biosensor can be improved.2.?Experimental Section2.1.

Materials2,2-Dimethoxy-2-phenylacetophenone (DMPP), sodium tetrakis [3,5-bis (trifluro-triethyl) phenyl] borate (NaTFPB), hydrogen ionophore I (tridodecylamine), sodium dihydrogen phosphate (NaH2PO4) were obtained from Fluka.

Sodium hydroxide (NaOH), sodium dodecyl sulphate (SDS), acetic acid, acetyl acetone from Systerm. In addition, 2-hydroxyethyl methacrylate (HEMA), poly(HEMA) commercial, 2-hexanediol diacrylate (HDDA), alcohol oxidase enzyme (AOX) from Hansenula polymorpha, bovine serum albumin (BSA), Bradford reagent, all were from Sigma Aldrich. N-acryloxysuccinimide (NAS) and tris(hydroxymethyl) aminomethane (Tris-HCl) were purchased from Acros Organics and Duchefa Biochemie, respectively.

Formaldehyde solution was obtained from BDH, n-butyl acrylate (nBA) from Merck, hydrochloride acid 37 % (HCl) from Riedel-de Haen, di-sodium hydrogen phosphate (Na2HPO4) from Hamburg Chemical, ammonium acetate from Scharlau while both Bactor agar and 1,4-dioxane were from Ajax Chemicals.

All chemicals were of analytical grade and used without further purification. Standard buffer solutions were prepared with deionized Batimastat water.2.2. Synthesis of Poly(nBA-NAS) MicrospheresPoly(nBA-NAS) microspheres were prepared via photopolymerization in the form of an emulsion. A mixture of 4 mL of nBA monomers, 0.09 g DMPP, 400 ��L HDDA, 0.1 g SDS, 10 mg NAS and 10 mL deionized water was prepared in a sample bottle. The resulting emulsion turned milky white after sonication for 5 min. The milky solution was then photocured for 300 s under continuous purging with nitrogen gas in an ultraviolet exposure unit (R.

S. Ltd.) of 15 Watt light intensity GSK-3 at a wavelength of 350 nm. Poly(nBA-NAS) microspheres were isolated by centrifugation (4,000 rpm, KUBOTA) for 8 min and finally washed a few times with 0.01 M sodium phosphate buffer solution (pH 8.0). Clean poly(nBA-NAS) microspheres were dried at room temperature and kept at 4 ��C when not in use.2.3.

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