Gold Bioconjugates

N. Khlebtsov, L. A. Dykman and V. A. Bogatyrev, Two-layer model of colloidal gold bioconjugates and its application to the optimization of nanosensors. Colloid Journal (in Russian), 65, 508-517 (2003). 

Pissuwan, D., Valenzuela, S.M., Killingsworth, M.C., Xu, X.D. and Cortie, M.B. (2007) Targeted destruction of murine macrophage cells with bioconjugated gold nanorods. Journal of Nanoparticle Research, 9, 1109-1124. 

The following sections discuss many of the major particle types and provide bioconjugation options for the coupling of ligands to the surface of functionalized particles. Some additional nanoparticle constructs, including gold particles, dendrimers, carbon nanotubes, Buckyballs and fullerenes, and quantum dots are discussed more fully elsewhere (see Chapter 7 Chapter 9, Section 10 Chapter 15 and Chapter 24). 

It is difficult to predict the effect of surface functionalization on the optical properties of nanoparticles in general. Surface ligands have only minor influence on the spectroscopic properties of nanoparticles, the properties of which are primarily dominated by the crystal field of the host lattice (e.g., rare-earth doped nanocrystals) or by plasmon resonance (e.g., gold nanoparticles). In the case of QDs, the fluorescence quantum yield and decay behavior respond to surface functionalization and bioconjugation, whereas the spectral position and shape of the absorption and emission are barely affected. 

Lin C-AJ, Yang T-Y, Lee C-H et al (2009) Synthesis, characterization, and bioconjugation of fluorescent gold nanoclusters toward biological labeling applications. ACS Nano 3 395 101... 

For example, Willner and co-workers accomplished electrical communication between glucose oxidase (GOx) and a gold electrode using molecular-level assembly.5,6 Unprecedentedly effective electron transfer was observed from the FAD moiety to the electrode through the Au-nano particles (electron transfer turnover rate, 4500 s-1), derived from molecular conjugation and bioconjugation. 

Qian XM, Zhou X, Me SM (2008) Surface-enhanced raman nanoparticle beacons based on bioconjugated gold nanocrystals and long range plasmonic coupling. J Am Chem Soc 130 14934-14935... 

Fig. 4.1. Amplified detection paths of a single-base mismatch in nucleic acids (a) using avidin and hiotin-labelled liposomes (h) using an avidin-Au-nanoparticle conjugate and the catalysed deposition of gold (c) using an avidin-alkaline phosphatase bioconjugate and the biocatalysed precipitation of the insoluble product 4. (Reproduced from Ref. [63] with permission from Elsevier.)...

Perhaps the biggest advantage of a water-based synthesis procedure is that bioconjugation of the gold and other metal/semiconductor nanopartides with DNA [32], enzymes [62], antibodies [63] etc. may be easily accomplished. 

Formation of bioconjugates with the gold nanoparticles is not possible in an organic environment and consequently, biological application of gold nanoparticles becomes difficult. 

Ojea-Jimenez I, Garcia-Fernandez L, Lorenzo J, Puntes VF (2012) Facile preparation of cationic gold nanoparticle-bioconjugates for cell penetration and nuclear targeting. ACS Nano 6(9) 7692-7702... 

El-Sayed s group has reported that use of a continuous near-IR laser induced cell destruction in the presence of bioconjugated gold nanorods [49]. This is because the... 

Goodman, C. M., McCusker, C. D., Yilmaz, T., and Rotello, V. M. (2004). Toxicity of gold nanoparticles functionalized with cationic and anionic side chains. Bioconjug Chem 15, 897-900. 

OPTICAL PROPERTIES AND BIOMEDICAL APPLICATIONS OF NANOSTRUCTURES BASED ON GOLD AND SILVER BIOCONJUGATES... 

Figure la shows that the maximal extinction increases with increasing adsorbed polymer shell thickness and shell refractive index. All curves have a maximum for gold core diameters 60-80 nm. This maximum is closely related to the optimizatiou problems discussed in Refs. [12, 17]. For small particles, the shift of extinction plasmon resonance can be described by a universal dependence [12, 51]. In the first approximatiorr, the optical properties of bioconjugates are well explained by a simple two-layer electrostatic model (previous analysis [43] contairrs some inacctrracies, see Ref [12]). We shall consider the extinction spectra only. For small conjugates, the extinction is determined by the absorption efficiency... 

Table 2. Dynamic light-scattering data for gold particles, their bioconjugates, and the adsorbed polymer shells.

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