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Molecules 2014, 19(4), 4997-5012; doi:10.3390/molecules19044997

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

1,* , 1, 1, 1, 2 and 1,*
1 Department of Applied Chemistry, National Chiayi University, Chiayi 60004, Taiwan 2 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.
Keywords: hyperbranched polymer; immobilization; magnetic nanocarrier hyperbranched polymer; immobilization; magnetic nanocarrier
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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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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