Biomolecule-nanoparticle interaction

Scheme 3.23 Different types of Au NP-biomolecule hybrids depending on biomolecule-nanoparticle interaction.

Au NPs functionalized with biomolecules can be synthesized using different methods, depending on factors inducing the interactions promoted between the nanoparticle and the biomolecule. These interactions can be classified as electrostatic adsorption, chemisorption and covalent binding and, finally, specific affinity interactions. Some examples are given in the following paragraphs (Scheme 3.23). 

The size of metal nanoparticles plays also a role in a quite different field of nanoscience the interaction with biosystems with nanoparticles in general, here especially with metal nanoparticles. Chapter 4 will deal with some very recent aspects considering the interaction of noble metal nanoparticles with biomolecules and living cells. 

Wet preparation of metal nanoparticles and their covalent immobilization onto silicon surface has been surveyed in this manuscript. Thiol-metal interaction can be widely used in order to functionalize the surface of metal nanoparticles by SAM formation. Various thiol molecules have been used for this purpose. The obtained functionalized particles can be purified to avoid the effect of unbounded molecules. On the other hand, hydrogen-terminated silicon surface is a good substrate to be covered by Si-C covalently bonded monolayer and can be functionalized readily by this link formation. Nanomaterials, such as biomolecules or nanoparticles, can be immobilized onto silicon surface by applying this monolayer formation system. 

Release of DNA in vivo takes place due to the increased acidic conditions inside living cells that result in the destabilization of the ORMOSIL-DNA complex. SiCVbased nanoparticles, in fact, do not release encapsulated biomolecules because of the strong hydrogen bonding between the biomolecule s polar centres and the silanols at the cage surface (as ORMOSIL-entrapped hydrophobic molecules are not leached in aqueous systems due to strong hydrophobic interactions).17... 

The third group of Au NP-biomolecule interactions are referred to as specific affinity interactions and include nanoparticles functionalized with groups that provide affinity sites for the binding of bio molecules such as proteins and oligonucleotides. 

Another plasmon resonance approach for detection of mercury vapour is based on localized plasmon resonance in gold nanoparticles deposited on transparent support (Fig. 12.4, right). Changes of the refractive index of gold nanoparticles due to adsorption of mercury should lead to modification of the gold plasmon band of optical adsorption spectra. This approach has been applied successfully for investigation of interaction of biomolecules however, to our knowledge there is still no report on its applications for detection of mercury vapour. 

The bottom-up techniques described herein are based on the use of nanosize building blocks to fabricate precisely organized solids at various scales. The final architecture of the solid, and the way these blocks combine with each other, can be conveniently adjusted by the synthesis conditions, the selection and modification of these nanoblocks, and their chemical functionality. The spontaneous arrangement of individual nanoblocks is generally obtained via self-assembly through weak interactions. The control over the organization of these components allows for the incorporation of nanoparticles, biomolecules, or chemical functionalities inside the solid structure in highly precise locations. 

The use of gold nanoparticles as an electrochemical label for bionanalysis was introduced by Costa-Garcia and coworkers 62 Adsorptive voltammetry was used to detect the gold signal and monitor biotin-stieptavidin interactions on a pretreated carbon paste electrode with an adsorbed biotinylated albumin layer after immersion into a solution of streptavidin-coated colloidal gold. While colloidal gold had found widespread use as a histochemical label for biomolecules and an optical label based on absorption... 

Interaction of biomolecules with the surface of metallic nanoparticles may also result in local changes in refraction index. This in turn may result in delicate modification of plasmon resonance frequency and yield detectable analytical signal [138],... 

The interaction of nanoparticles with the proteins is governed from the same type of interactions described for carbon nanotubes. Since NPs carry charges, they can electrostatically adsorb biomolecules with different charges, which depend on the pH that the immobilization takes place and the pi of the protein [3,191]. Moreover, hydrophobic interactions, hydrogen bonds and non-specific absorption can play a role for enzyme non-covalent adsorption onto the surface of nanoparticles. 

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