Properties and applications of proteins encapsulated within sol–gel derived materials

Jin, Wen; Brennan, John D.

doi:10.1016/s0003-2670(02)00229-5

Cited by 496 publications

(386 citation statements)

References 250 publications

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“…We do so by using the sol-gel materials methodology for enzyme entrapment [1]. Sol-gel entrapped enzymes [2][3][4] have already been shown to provide significant thermal stability [5][6][7][8], stability to extreme pH values [9][10][11], and stability to non-native environments [12][13][14]. In these earlier studies the protectability was attributed to the encaging itself [15]; here we extend these observations by showing protection against an oxidant due to active chemical scavenging of the destructive chemical by the matrix.…”

Section: Introductionsupporting

confidence: 64%

Erratum to: Preserving the activity of enzymes under harsh oxidizing conditions: sol–gel entrapped alkaline phosphatase exposed to bromine

Frenkel-Mullerad

Ben-Knaz

Avnir

2014

J Sol-Gel Sci Technol

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Chemically reactive sol-gel matrices hold the ability of protecting entrapped enzymes from destruction by external harsh chemicals. We show this concept by exposing alkaline phosphatase (AlP) to a strong oxidizing agent-bromine. In solution, AlP is immediately destroyed by this oxidant. When AlP was entrapped in hybrid silica sol-gel materials carrying double bonds, the reactivity of AlP was preserved after exposure to bromine under conditions which totally destroy it in solution. The matrices studied were vinylated and allylated silicas, and their protectability was compared to n-alkylated silicas and to silica itself. For instance, the reactivity of AlP entrapped in allylated silica after exposure to 25.6 mM bromine solution is 40 times higher than its reactivity when entrapped in pure silica; and in solution the enzyme is totally destroyed at this concentration. Molecular level mechanisms for these observations are proposed.Keywords Sol-gel Á Sol-gel preserved enzymes Á Oxidizing agent Á Ormosil BackgroundAlkaline phosphatase (AlP), like most other enzymes, is totally destructed when exposed to a strong oxidant such as bromine. Here we show how to protect an enzyme when exposed to such conditions. We do so by using the sol-gel materials methodology for enzyme entrapment [1]. Sol-gel entrapped enzymes [2-4] have already been shown to provide significant thermal stability [5][6][7][8], stability to extreme pH values [9][10][11], and stability to non-native environments [12][13][14]. In these earlier studies the protectability was attributed to the encaging itself [15]; here we extend these observations by showing protection against an oxidant due to active chemical scavenging of the destructive chemical by the matrix. Thus when the enzyme is entrapped within sol-gel derived olefinated silicas, and then exposed to bromine solution, the double bonds react with the bromine, and protect the enzyme. By comparing this mode of protection to entrapments in non-reactive matrices-sol-gel derived silicas and sol-gel-derived alkylated silicas-we were able to evaluate the weights of the bromine scavenging and of the physical entrapment to the protection of the enzyme; we find that this relative weight depends on the alkyl and alkenyl chain. Thus, the hybrid sol-gel material we used was based on vinyl (CH 2 =CH-Si; VTS; here and below we use the name of the monomer as the name of the material), or allyl (CH 2 =CH-CH 2 -Si; ATS). In earlier studies we showed these olefinated sol-gel materials are highly reactive towards bromine, undergoing in water an hydrobromination reaction [16,17] which proceeds according to Markovnikov's rule [18], as shown in Scheme 1, resulting in a bromohydrin and HBr. The formation of an acid is an environmental change that the entrapped enzyme can withstand. We recall that we showed that sol-gel entrapped alkaline phosphataseThe online version of the original article can be found under

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Section: Introductionsupporting

confidence: 64%

Erratum to: Preserving the activity of enzymes under harsh oxidizing conditions: sol–gel entrapped alkaline phosphatase exposed to bromine

Frenkel-Mullerad

Ben-Knaz

Avnir

2014

J Sol-Gel Sci Technol

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“…Promising results have been obtained for enzyme encapsulation in inorganic matrices such as silica synthesized by sol-gel processes 9,[23][24][25] . Encapsulation within silica networks provides soft immobilization conditions that prevent denaturalization of biomolecules upon encapsulation 26,27 .…”

Section: Introductionmentioning

confidence: 99%

Modulation of the Silica Sol–Gel Composition for the Promotion of Direct Electron Transfer to Encapsulated Cytochrome c

et al. 2014

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The direct electron transfer between indium-tin oxide electrodes (ITO) and cytochrome c encapsulated in different sol-gel silica networks was studied. Cyt c@silica modified electrodes were synthesized by a two-step encapsulation method mixing a phosphate buffer solution with dissolved cytochrome c and a silica sol prepared by the alcohol free sol-gel route. These modified electrodes were characterized by cyclic voltammetry, UV-visible spectroscopy and in situ UV-visible spectroelectrochemistry.The electrochemical response of encapsulated protein is influenced by the terminal groups of the silica pores. Cyt c does not present electrochemical response in conventional silica (hydroxyl terminated) or phenyl terminated silica. Direct electron transfer to encapsulated cytochrome c and ITO electrodes only takes place when the protein is encapsulated in methyl modified silica networks.

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“…In the past few years, numerous silica-and/or porous siloxane-based organic-inorganic materials have been employed to produce protein-doped hybrid materials as biosensors and as heterogeneous catalysts for industrial applications [1][2][3][4][5][6]. In particular, the design of organically-modified hydrophobic glasses for encapsulating lipases, a class of enzymes that mediate lipid reactions and function naturally at hydrophobic interfaces, has received much attention due to the potential application of these enzymes in the conversion of fats and oils to other products of value [7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

et al. 2008

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Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′) 3 , featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0-15%. At a fixed molar content of 5% RSi(OR') 3 , the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices.

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Properties and applications of proteins encapsulated within sol–gel derived materials

Cited by 496 publications

References 250 publications

Erratum to: Preserving the activity of enzymes under harsh oxidizing conditions: sol–gel entrapped alkaline phosphatase exposed to bromine

Erratum to: Preserving the activity of enzymes under harsh oxidizing conditions: sol–gel entrapped alkaline phosphatase exposed to bromine

Modulation of the Silica Sol–Gel Composition for the Promotion of Direct Electron Transfer to Encapsulated Cytochrome c

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

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