Microenvironment surface modification

As far as enzyme immobilization is concerned, the biocompatibility of support is another important requirement [120-123], as the biocompatible surface can reduce some non-biospecific enzyme-support interactions, create a specific microenvironment for the enzymes and thus provide substantial benefits to the enzyme activity [124], To increase the biocompatibility of the support, various surface modification protocols have often been used to introduce a biofriendly interface on the support surface, such as coating, adsorption, self-assembly and graft polymerization. Among these methods, it is relatively easy and effective to directly tether natural macromolecules on the support surface to form a biomimetic layer for enzyme immobilization. In fact, this protocol has been used in tissue engineering recently [125-127]. 

To obviate such problems, several surface modification techniques have been studied and their efficacy tested both in vitro and in vivo. Physical methods involve oxidation of PDMS surface and adsorption of (natural or synthetic) polymers. Often, the hydrophilic microenvironment provided by... 

The major drawback of this reaction system is the high energy and equipment costs due to the use of high pressures. In addition, the use of supercritical carbon dioxide can have adverse effects on enzymes, for example, by decreasing the pH of the microenvironment of the enzyme, by the formation of carbamates owing to covalent modification of free amino groups at the surface of the protein and by deactivation during pressurisation-depressurisation cycles [4]. 

Nanoparticles have been used extensively for the immobilization of biomolecules [3]. In addition to their biocompatibility they can produce a unique microenvironment that provides improvement in the freedom of orientation for affinity binding with advantages over planar substrates, an increase in surface area for higher probe loading capacities, and enhanced diffusion of amplification agents. Modification of electrode surfaces with nanoparticles can be carried out by simple electrostatic adsorption or covalent attachments such... 

Whereas DNA is a relatively simple polyanion and can be modified and easily immobilized on solid surfaces based on electrostatic interactions or covalent bonding, protein bonding is much more delicate. The complexity derives from a multitude of biochemical properties. Protein molecules possess particular three-dimensional structures and varying chemical and physical properties (e.g., hydrophilic and hydrophobic domains, ionic interactions), and the activity and function as well as the partial charge of domains depend on the local physical and chemical microenvironment. Additionally, complexity is further increased by posttranscriptional modifications of protein conformation hence the well-established on-chip approaches of oligonucleotide microarrays are not applicable to protein microarrays. For protein microarray production, four major requirements have to be fulfilled ... 

Recently, our group has developed a structured polymer scaffold which is made of perforated polycarbonate thin film. The scaffold provides a three-dimensional microenvironment to cell culture and is continuously perfused with the nutrient medium [31]. Therefore, polycarbonate chemistry is of particular interest for our applications with a special focus on the mild reaction conditions. Moreover, most of the methods described above are for post modification of the surface of polycarbonate using aggressive reaction conditions. In this chapter we describe a mild and efficient method for the functionalization of polycarbonate using terminal diamines. 

The diffusion of reactants and products in porous-material-based nanoreactor could be greatly affected by the surface properties, which in turn could influence the catalytic activity and even selectivity of a chemical reaction taking place in the confined nanospace. Generally, organic molecules are hydrophobic and the silica-based mesoporous nanopores are hydrophihc. The difficulty in the diffusion of reactants and products in hydrophobic nanopores may reduce the reaction conversions [123]. Thus, the surface hydrophobic modification of the nanopore may benefit fast diffusion of the substrate, which may, in turn, contribute to the improved activity. When a reaction involves incompatible substrates, such as oil and water, the amphiphilic modification of the nanopore microenvironment is a smart strategy because the amphiphilic nanopore should provide a microenvironment... 

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