Surface immobilization, covalent

Chen H, Zhang Z, Chen Y, Brook MA, and Sheardown H. Protein repeUant silicone surfaces by covalent immobilization of poly(ethylene oxide). Biomaterials, 2005, 26, 2391-2399. 

The following protocol for passive adsorption is based on methods reported for use with hydrophobic polymeric particles, such as polystyrene latex beads or copolymers of the same. Other polymer particle types also may be used in this process, provided they have the necessary hydrophobic character to promote adsorption. For particular proteins, conditions may need to be optimized to take into consideration maximal protein stability and activity after adsorption. Some proteins may undergo extensive denaturation after immobilization onto hydrophobic surfaces therefore, covalent methods of coupling onto more hydrophilic particle surfaces may be a better choice for maintaining native protein structure and long-term stability. 

In heterogeneous systems, the reagent can be immobilized on a solid surface either covalently, behind a membrane, or by absorption, and it can interact... 

The first report of surface-immobilized dendrimers was in 1994 [54]. Subsequently, our research group showed that the amine-terminated PAMAM and PPl dendrimers could be attached to an activated mercaptoimdecanoic acid (MUA) self-assembled monolayer (SAM) via covalent amide linkages [55, 56]. Others developed alternative surface immobilization strategies involving metal com-plexation [10] and electrostatic binding [57]. These surface-confined dendrimer monolayers and multilayers have found use as chemical sensors, stationary phases in chromatography, and catalytic interfaces [41,56,58,59]. Additional applications for surface-confined dendrimers are inevitable, and are dependent only on the synthesis of new materials and the development of clever, new immobilization strategies. 

Examples of surface-immobilized mediators are electropolymerized azines for electro-oxidation of The extreme form of this approach is formation of biocatalytic monolayer, comprising a surface-bound mediator species that is itself bound to a single enzyme molecule. Katz et al. report a complete cell based on novel architecture at both electrodes (Figure 7). On the anode side, the FAD center of glucose oxidase is removed from the enzyme shell and covalently attached to a pyrroloquinoline quinone (PQQ) mediator species previously immobilized on a gold surface. The GOx apoenzyme (enzyme with active center removed) is reintroduced in solution and selectively binds to FAD, resulting in a PQQ-... 

There are three principal approaches used for the immobilization of electroactive substances onto surfaces chemisorption, covalent bonding, and film deposition. 

Another label-free optical detection method—FTIR-ATR—has been applied for detection of thrombin by means of DNA aptamers [73], The antithrombin DNA aptamer previously developed by Tasset et al. [17] was immobilized covalently onto Si surface using UV irradiation method. As a quantitative measure, the area of N-H and CH2 bands was used. This method allowed to detect thrombin with a sensitivity around 10 nmol/L. The specificity of binding of protein to aptamer was also investigated using DNA with no binding site for thrombin. It has been noted that for effective binding study by FTIR-ATR method, the concentration of protein should be kept lower than 100 nmol/L. 

Table 1 Covalent surface immobilization of proteinic affinity ligands [ 124]...

Husar GM, Anziano DJ, Leuck M, Sebesta DP (2001) Covalent modification and surface immobilization of nucleic acids via the Diels-Alder bioconjugation method. Nucleosides Nucleotides Nucleic Acids 20 559-566... 

Chen, H., Zhang, Z., Chen, Y., Brook, M. A., Sheardown, H. Protein Repellant Silicone Surfaces by Covalent Immobilization of Poly(Ethylene Oxide), Biomaterials 2005,26, 2391. 

Different methods are used to immobilize covalently the proteins to HPLC supports. The coupling procedures imply various activation chemistries via epoxide-, diol-, or aldehyde-silica [51,52], Generally, the immobilized antibodies are randomly oriented. Dihydrazide-silica supports are used for an oriented immobilization of the antibody through its carbohydrate residues [53]. Another approach is to bind the antibody to protein A or protein G surfaces [17]. The antibody will bind through the Fc portion, leaving the antigen combining sites oriented away from the support. 

The immobilization of dsDNA and ssDNA to surfaces can be attained very easily by adsorption. No reagents or DNA modifications occur since the immobilization does not involve formation of covalent bonds with the surface. Surface immobilization of ssDNA by covalent binding, described by Thompson and co-workers [12], is convenient in DNA-hybridization sensing because it enables probe structure flexibility with respect to changes in its conformation to occur, such that hybridization can take place without the probe being removed from the sensor surface. However, non-selective adsorption of non-complementary ssDNA, added to bulk solution, also occurs at multiple sites in the interstitial regions on the sensor surface between immobilized ssDNA strands. The effects of selective and non-selective binding influence the detection of hybridization of the immobilized strands, as found by ICrull and co-workers [13]. 

An immunological method has been developed based on AFBj antibody-functionalised composite magnetic nano particles based on FejO SiO. For this purpose anti-AFBj is immobilized covalently on the surface of the nucleus. Te selectivity, reproducibility and stability of the immunological system are within the allowable error. Compared to the conventional ELISA the proposed immunosystem is simple and rapid (Li Wang and Xian-Xue Gan 2009). 

Figure 2.70 Immobilization of Cso on surfaces, (a) Covalent linking to gold or to indium-tin oxide and noncovalent attachment to gold modified with coronene ( RSC 2005) ...

The primary methods used in cell immobilization are surface adhesion, covalent attachment and entrapment. Surface adhesion involves adsorption of cells to microcarriers such as calcium alginate beads, collagen-coated plastic beads, diatomite silica, and dextrans [68]. Immobilization can be achieved simply by suspending the cells and microcarrier together under slow agitation. Examples of such systems include immobilized bacteria for waste water treatment and adsorbed Azotobacter vinelandii on Cellex E for nitrogen fixation... 

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