Biopolymer immobilized

The next publication appeared in 1984. Venton et al. [67] entrapped antiprogesterone antiserum into a sol-gel derived silica. It retained about 56 % of progesterone binding capacity. The authors mentioned the considerable promise of the sol-gel technique for biopolymer immobilization, but their study was not further continued. 

Here ps is the biopolymer immobilization density A2us = 2%D /3 is the second virial coefficient based on excluded volume for a biopolymer of equivalent diameter D (a sphere of equal volume) (Neal and Lenhoff, 1995) and = As/V0 is the chromatographic phase ratio. The surface area As accessible to the biopolymer in the mobile phase is available in the literature, especially for proteins (Tessier et al., 2002 Dumetz et al., 2008). 

Mikhailov, O. V.. Self-Assembly of Molecules of Metal Macrocyclic Compounds in Nanoreactors on the Basis of Biopolymer-Immobilized Matrix Systems. Nanotechnol. Russ., (1-2), 1825 (2010). 

Selectivity is an important consideration in analytical chemistry. Biologically derived polymers can be used as highly selective immobilized reagents in analytical appHcations. The first reported use of immobilized biopolymers as biosensors (qv) for the detection of an analyte was made in 1962 (48). Since that first reported use there has been a great deal of development and appHcation of immobilized biopolymers in analytical chemistry. 

Immobilized Enzymes. The immobilized enzyme electrode is the most common immobilized biopolymer sensor, consisting of a thin layer of enzyme immobilized on the surface of an electrochemical sensor as shown in Figure 6. The enzyme catalyzes a reaction that converts the target substrate into a product that is detected electrochemicaHy. The advantages of immobilized enzyme electrodes include minimal pretreatment of the sample matrix, small sample volume, and the recovery of the enzyme for repeated use (49). Several reviews and books have been pubHshed on immobilized enzyme electrodes (50—52). 

Fig. 17 (a) Elastin-based stimulus-responsive gold nanoparticles. Reproduced from [131] by permission of The Royal Society of Chemistry (b) Functionalization of a glass surface with ELP. In the first step, the glass surface is aminosilylated with N-2-(aminoethyl)-3-aminopropyl-trimethoxysilane, then modified with glutaraldehyde. Subsequently, the stimulus-responsive biopolymer is covalently immobilized using reductive amination. Reproduced from [132] by permission of The Royal Society of Chemistry... 

In another investigation, ELP[V5L2G3-90] with three lysines in the N-terminal region was immobihzed on a glass surface in a microreactor to enable temperature-controlled positioning of ELP fusion proteins. For this purpose, the glass surface was first functionalized with A -2-(aminoethyl)-3-aminopropyltrimethoxysilane, followed by glutaraldehyde treatment and reductive amination to immobilize the biopolymer on the surface (Fig. 17b) [132]. 

These examples demonstrate that additives can have a beneficial effect on the entrapped biopolymers. Unfortunately, they are generally not universal. The additives need to be found for individual immobilized biopolymers and that is not so easy to do. For instance, lactate oxidase retained its activity in a silica matrix if the enzyme was taken as a complex with poly(N-vinylimidazole) prior to the immobilization, but the polymer did not stabilize glycolate oxidase [87,114], Its stabilization was observed after an exchange of poly(N-vinylimidazole) for poly(ethyleneimine). This is a decisive disadvantage of the approaches because they do not offer a general solution that might be extended to any immobilized biopolymer. 

In this chapter, immobilization of proteins on these mesoporous silicas and PMO is first introduced, followed by a description of protein immobilization on mesoporous carbon materials. The adsorption behavior of other biopolymers such as... 

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

Layered materials are of special interest for bio-immobilization due to the accessibility of large internal and external surface areas, potential to confine biomolecules within regularly organized interlayer spaces, and processing of colloidal dispersions for the fabrication of protein-clay films for electrochemical catalysis [83-90], These studies indicate that layered materials can serve as efficient support matrices to maintain the native structure and function of the immobilized biomolecules. Current trends in the synthesis of functional biopolymer nano composites based on layered materials (specifically layered double hydroxides) have been discussed in excellent reviews by Ruiz-Hitzky [5] and Duan [6] herein we focus specifically on the fabrication of bio-inorganic lamellar nanocomposites based on the exfoliation and ordered restacking of aminopropyl-functionalized magnesium phyllosilicate (AMP) in the presence of various biomolecules [91]. 

An alumina matrix may be prepared with high pore density (more than 60 %) and pore diameters ranging from 5 to 250 nm. Ruiz-Hitzky et al. [214] immobilized GOD in nanoporous alumina membranes with regular hexagonal arrays of highly ordered cylindrical pores aligned perpendicularly to the membrane surface. GOD was anchored in the membrane by the highly hydrophilic chitosan biopolymer. Full activity was maintained for at least 50 hours. 

Henderson, W., Olsen, G.M., and Bonnington, L.S. (1994) Immobilized phosphines incorporating the chiral biopolymers chitosan and chitin./. Chem. Soc. Comm., 1863-1864. 

In view of the conductive and electrocatalytic features of carbon nanotubes (CNTs), AChE and choline oxidases (COx) have been covalently coimmobilized on multiwall carbon nanotubes (MWNTs) for the preparation of an organophosphorus pesticide (OP) biosensor [40, 41], Another OP biosensor has also been constructed by adsorption of AChE on MWNTs modified thick film [8], More recently AChE has been covalently linked with MWNTs doped glutaraldehyde cross-linked chitosan composite film [11], in which biopolymer chitosan provides biocompatible nature to the enzyme and MWNTs improve the conductive nature of chitosan. Even though these enzyme immobilization techniques have been reported in the last three decades, no method can be commonly used for all the enzymes by retaining their complete activity. 

The biomembrane-like films can provide a favorable microenvironment for proteins and enhance direct electron-transfer rate between proteins and electrodes, so many biopolymers such as methyl cellulose (MC) and dihexadecylphospate (DHP) have been used to immobilize Mb and make biosensors [230-232], The electrochemical catalytic reduction of oxygen by the Mb-MC/EPG was examined by CVs. Mb-MC... 

Biopolymers such as agarose hydrogel can also be used to immobilize HRP and to reduce oxygen, hydrogen peroxide and nitric oxide [231], For an HRP-agarose/EPG in a pH 7.0 PBS, a reduction peak at -0.30V was observed after addition of H2Q2. 

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