Biomolecule-nanoparticle attachments

An application of biomolecule-nanoparticle hybrid supramolecular assemblies is the sensitive detection of p53, a tumor suppressor protein, by AuNP streptavidin conjugates capped with multiple ferrocene molecules.26 As shown in Figure 8.6, a mixed monolayer of double-stranded DNA and 1-hexanethiol on an Au electrode is used to capture p53, which binds to DNA containing the consensus site sequence. Subsequent conjugation of the captured p53 with biotin allowed for attachment of... 

In 1994, thiols were firstly used as stabilizers of gold nanoparticles [6a]. Thiols form monolayer on gold surface [18] and highly stable nanoparticles could be obtained. Purification of nanoparticles can be carried out, which makes chemical method of metal nanoparticles a real process for nanomaterial preparation. Various thiol derivatives have been used to functionalize metal nanoparticles [6b, 19]. Cationic and anionic thiol compounds were used to obtain hydrosols of metal nanoparticles. Quaternary ammonium-thiol compounds make the nanoparticle surface highly positively charged [20]. In such cases, cationic nanoparticles were densely adsorbed onto oppositely charged surfaces. DNA or other biomolecule-attached gold nanoparticles have been proposed for biosensors [21]. 

Nanoparticle surface modification is of tremendous importance to prevent nanoparticle aggregation prior to injection, decrease the toxicity, and increase the solubility and the biocompatibility in a living system [20]. Imaging studies in mice clearly show that QD surface coatings alter the disposition and pharmacokinetic properties of the nanoparticles. The key factors in surface modifications include the use of proper solvents and chemicals or biomolecules used for the attachment of the drug, targeting ligands, proteins, peptides, nucleic acids etc. for their site-specific biomedical applications. The functionalized or capped nanoparticles should be preferably dispersible in aqueous media. 

Baca, A. J. Zhou, F. M. Wang, J. Hu, J. B. Li, J. H. Wang, J. X. Ghikneyan, Z. S. Attachment of ferrocene-capped gold nanoparticle-streptavidin conjugates onto electrode surfaces covered with biotinylated biomolecules for enhanced voltammetric analysis. Electroanalysis 2004, 16, 73-80. 

LSPR absorption bands are characteristic of the type of nanomaterial, the diameter of nanoparticles, and their distribution (Freeman et al., 1995 Nath and Chilkoti, 2002). LSPR can detect an immediate change in the interfacial refractive index (RI) of the surrounding medium (Mock et al., 2003 Raschke et al., 2003 Nath and Chilkoti, 2004), which is greatly affected by the attachment of biomolecules at the colloid-solution interface (Himmelhaus and Takei, 2000 Mock et al., 2003 Raschke et al., 2003 Nath and Chilkoti, 2004 Endo et al.,... 

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... 

---