Hybrid enzyme-nanoparticle

Figure 3-10. The assembly of an Au-nanoparticle (1.4 nm) electrically contacted glucose oxidase electrode by (a) the primary reconstitution of apo-GOx on the FAD-functionalized Au-nanoparticle, and the immobilization of the enzyme-nanoparticle hybrid on an electrode surface (b) the primary immobilization of the FAD-modified Au-nanoparticle on tire electrode surface and the surface reconstitution of apo-GOx on the functionalized electrode. Reproduced with permission from ref. 41. Copyright 2003, AAAS.

However, it has to be realized that biological templates remain inserted in the final nanoparticles and this is not acceptable for many applications. Nevertheless, some recent examples indicate that such biomimetic materials may be suitable for the design of biotechnological and medical devices [32]. For instance, it was shown that silica gels formed in the presence of p-R5 were excellent host matrices for enzyme encapsulation [33]. In parallel, biopolymer/silica hybrid macro-, micro- and nanocapsules were recently obtained via biomimetic routes and these exhibit promising properties for the design of drug delivery materials (see Section 3.1.1) [34,35],... 

Biomaterials such as proteins/enzymes or DNA display highly selective catalytic and recognition properties. Au nanoparticles or nanorods show electronic, photonic and catalytic properties. The convergence of both types of materials gives rise to Au NP-biomolecule hybrids that represent a very active research area. The combination of properties leads to the appearance of biosensors due to the optical or electrical transduction of biological phenomena. Moreover, multifunctional Au NP-peptide hybrids can be used for targeting nuclear cells where genetic information is stored and could be useful for biomedical applications [146]. 

Metallic nanoparticles and single-walled carbon nanotubes (SWCNTs) exhibit nanoscale dimensions comparable with the dimensions of redox proteins. This enables the construction of NP-enzyme or SWCNT-enzyme hybrids that combine the unique conductivity features of the nanoelements with the biocatalytic redox properties of the enzymes, to yield wired bioelectrocatalyts with large electrode surface areas. Indeed, substantial advances in nanobiotechnology were achieved by the integration of redox enzymes with nanoelements and the use of the hybrid systems in different bioelectronic devices.35... 

Enzymes functionalized with metallic NPs were used as biocatalytic hybrids for the growth of metallic nanowires. The catalytic enlargement of metal nanoparticles by products generated by different enzymes was used to develop different optical sensors that follow the activities of enzymes and analyze their substrates.57 For example, hydrogen peroxide generated by the biocatalyzed oxidation of glucose by O2 in the... 

Eby DM, Luckarift HR, Johnson GR (2009) Hybrid antimicrobial enzyme and silver nanoparticle coatings for medical instruments. ACS Appl Mater Interfaces 1 1553-1560... 

Willner I Basnar B Willner B, Nanoparticle-enzyme hybrid systems for nanobiotechnology, FEBS J., 2007, 274, 302-309. 

Niemeyer et al. have reported the design of quantum dot/enzyme nanohybrids that are capable of catalyzing an organic transformation upon optical excitation of semiconductor quantum dots (QDs) [31]. The hybrid device was composed of semiconductor CdS nanoparticles and cytochrome p450BSp enzyme. It has been proposed that irradiation of QDs leads to formation of excitons (h+-e pairs) that on dissociation generate superoxide and hydroxyl radicals in interfacial electron transfer process (see Chapter 7). These radicals in turn activate the enzyme adsorbed at the QD surface. The activated enzyme is able to catalyze mono-oxygenation of fatty acids, but has a lower activity than the native enzyme [31]. 

Commonly used labels for targets are fluorescence dyes that are usually covalently attached on the 5 -end. Enzyme labels and nanoparticles are also used for photometric detection. As a consequence, the signal intensities of hybridized probes are quite small and therefore detection and quantification requires high instrumental sensitivity. Non-specific interactions between the targets and the solid support material, and incorrect and incomplete immobilizations of probes leads to inhomogeneous spot morphology, which complicates the interpretation of the data. 

Willner, L, Basnar, B., and Willner, B. (2007) Nanoparticle-enzyme hybrid... 

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