Design of multifunctionalized γ-Fe 2 O 3 @SiO 2 core–shell nanoparticles for enzymes immobilization

Journal of Nanoparticle Research (Impact Factor: 2.18). 02/2010; 12(2):675-680. DOI: 10.1007/s11051-009-9757-0


This article deals with the first covalent grafting of an enzyme on twice functionalized γ-Fe2O3@SiO2 core–shell magnetic nanoparticles. First, amino-PEG functionalized nanoparticles were synthesized in order to comply with
non-toxic platforms that would be stable in high concentration and would exhibit chemical groups to allow further coupling
with biomolecules. This approach produces a colloidal suspension of covalently grafted enzymes that remains stable for months
and mimics the enzyme–substrate interactions in solution. Secondly, nanoparticles synthesis and enzyme coupling process were
reported and the catalytic properties of bound enzymes were measured and compared with that of the free one. These new materials
appear to be useful tools for enzymatic catalysis research and may be extended to other biomolecules. Furthermore, magnetic
properties of these materials open the way to separation, purification, and transport under magnetic field.

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    • "Increases in the K M value following BGL immobilisations on gamma-Fe2O3@SiO2 core-shell magnetic nanoparticles have also been reported [31]. The minor change in apparent K M values suggested that the substrate binding affinity of the enzyme active site was altered by immobilisation. "
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    ABSTRACT: BackgroundPrevious research focused on pretreatment of biomass, production of fermentable sugars and their consumption to produce ethanol. The main goal of the work was to economise the production process cost of fermentable sugars. Therefore, the objective of the present work was to investigate enzyme hydrolysis of microcrystalline cellulose and hemp hurds (natural cellulosic substrate) using free and immobilised enzymes. Cellulase from Trichoderma reesei was immobilised on an activated magnetic support by covalent binding and its activity was compared with that of the free enzyme to hydrolyse microcrystalline cellulose and hemp hurds on the basis of thermostability and reusability.ResultsUp to 94% protein binding was achieved during immobilisation of cellulase on nanoparticles. Successful binding was confirmed using Fourier transform infrared spectroscopy (FTIR). The free and immobilised enzymes exhibited identical pH optima (pH 4.0) and differing temperature optima at 50°C and 60°C, respectively. The K M values obtained for the free and immobilised enzymes were 0.87 mg/mL and 2.6 mg/mL respectively. The immobilised enzyme retained 50% enzyme activity up to five cycles, with thermostability at 80°C superior to that of the free enzyme. Optimum hydrolysis of carboxymethyl cellulose (CMC) with free and immobilised enzymes was 88% and 81%, respectively. With pretreated hemp hurd biomass (HHB), the free and immobilised enzymes resulted in maximum hydrolysis in 48 h of 89% and 93%, respectively.ConclusionThe current work demonstrated the advantages delivered by immobilised enzymes by minimising the consumption of cellulase during substrate hydrolysis and making the production process of fermentable sugars economical and feasible. The activity of cellulase improved as a result of the immobilisation, which provided a better stability at higher temperatures. The immobilised enzyme provided an advantage over the free enzyme through the reusability and longer storage stability properties that were gained as a result of the immobilisation.
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    ABSTRACT: We examine the impact on market liquidity of the presence of financial intermediaries that are informed and active participants in both the equity and the syndicated bank loan markets. We identify the presence of informationally advantaged lead arrangers of syndicated bank loans that simultaneously act as equity market makers, denoted dual market makers. By employing a two-stage procedure with instrumental variables, we identify the simultaneous equations model of liquidity and dual market maker decisions. We find empirical support for our theoretical model's predictions that the presence of dual market makers improves the liquidity of more competitive equity markets but widens the spread in the less competitive loan market.
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    ABSTRACT: This work combined two tools, giant unilamellar vesicles (GUVs) and core-shell magnetic nanoparticles (CSMNs), to develop a simplified model for studying interactions between the cell membrane and nanoparticles. We focused on charged functionalized CSMNs that can be either cationic or anionic. Using optical, electron, and confocal microscopy, we found that giant vesicle-nanoparticle interactions did not result from a simple electrostatic phenomenon because cationic CSMNs tended to bind to positively charged bilayers, whereas anionic CSMNs remained inert.
    Langmuir 10/2010; 26(20):16025-30. DOI:10.1021/la1023746 · 4.46 Impact Factor
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