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Molecules 2014, 19(4), 4997-5012;

Surface-Functionalized Hyperbranched Poly(Amido Acid) Magnetic Nanocarriers for Covalent Immobilization of a Bacterial γ-Glutamyltranspeptidase

Department of Applied Chemistry, National Chiayi University, Chiayi 60004, Taiwan
Institute of Molecular Biology, Academia Sinica, Nankang District, Taipei 11529, Taiwan
Authors to whom correspondence should be addressed.
Received: 11 March 2014 / Revised: 15 April 2014 / Accepted: 17 April 2014 / Published: 22 April 2014
(This article belongs to the Special Issue Enzyme Immobilization)
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In this study, we synthesized water-soluble hyperbranched poly(amido acid)s (HBPAAs) featuring multiple terminal CO2H units and internal tertiary amino and amido moieties and then used them in conjunction with an in situ Fe2+/Fe3+ co-precipitation process to prepare organic/magnetic nanocarriers comprising uniformly small magnetic iron oxide nanoparticles (NP) incorporated within the globular HBPAAs. Transmission electron microscopy revealed that the HBPAA-γ-Fe2O3 NPs had dimensions of 6–11 nm, significantly smaller than those of the pristine γ-Fe2O3 (20–30 nm). Subsequently, we covalently immobilized a bacterial γ-glutamyltranspeptidase (BlGGT) upon the HBPAA-γ-Fe2O3 nanocarriers through the formation of amide linkages in the presence of a coupling agent. Magnetization curves of the HBPAA-γ-Fe2O3/BlGGT composites measured at 300 K suggested superparamagnetic characteristics, with a saturation magnetization of 52 emu g−1. The loading capacity of BlGGT on the HBPAA-γ-Fe2O3 nanocarriers was 16 mg g−1 support; this sample provided a 48% recovery of the initial activity. The immobilized enzyme could be recycled 10 times with 32% retention of the initial activity; it had stability comparable with that of the free enzyme during a storage period of 63 days. The covalent immobilization and stability of the enzyme and the magnetization provided by the HBPAA-γ-Fe2O3 NPs suggests that this approach could be an economical means of depositing bioactive enzymes upon nanocarriers for BlGGT-mediated bio-catalysis. View Full-Text
Keywords: hyperbranched polymer; immobilization; magnetic nanocarrier hyperbranched polymer; immobilization; magnetic nanocarrier

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Juang, T.-Y.; Kan, S.-J.; Chen, Y.-Y.; Tsai, Y.-L.; Lin, M.-G.; Lin, L.-L. Surface-Functionalized Hyperbranched Poly(Amido Acid) Magnetic Nanocarriers for Covalent Immobilization of a Bacterial γ-Glutamyltranspeptidase. Molecules 2014, 19, 4997-5012.

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