The GNPs used in this study were synthesized by sodium borohydride reduction of tetrachloroaurate. As previously reported, the presence of a surface plasmon resonance band at ca. 510 nm confirms the formation of spherical gold nanoparticles. The formation of spherical GNPs and their 5 nm size diameter was further confirmed by TEM. The SCH 442416 GNP-C225 conjugates were then synthesized using this naked GNP solution and purified as described in the materials and methods section. The antibody spontaneously binds to the GNPs through Au-S and Au-N bonding. The production of GNPC225 was monitored by UV-Vis spectroscopy. It is evident that with the addition of C225 there is a gradual red shift in the SPR band of the naked gold, from 510 nm to 519 nm. Such a red shift in the SPR band of the GNPs suggests the perturbation of the electrical double layer by the antibody surrounding the GNPs and thus indicates binding of the antibody to the nanoparticles. To further confirm the GNP-C225 conjugation we challenged the nanoconjugates against salt induced aggregation. Addition of 140 mM NaCl has been reported to result in aggregation of naked or partially covered particles, such aggregation leads to a dramatic red shift in the SPR band. The absorption spectra of the nanoconjugates were recorded 15 minutes after incubation with 140 mM of sodium chloride. As expected, the naked GNPs showed a drastic red shift in the SPR band from 510 nm to around 600 nm confirming aggregation of uncovered nanoparticles. Salt induced aggregation was directly related to the increased loading of C225 on the GNP surface, hence the SPR band completely disappeared at a C225 to GNP ratio of 3 suggesting the absence of available reactive surface to salt induced aggregation. Targeted SSR 69071 delivery of inorganic nanomaterials is an essential area of research for nanomedicine. Unique physicochemical properties of inorganic nanomaterials may be utilized for several biomedical applications such as detection/diagnosis, therapy and imaging. Thus, it is important to define the design parameters to specifically deliver nanoconjugates to the cells of interest. There are several key factors that may define the success of targeted delivery; selection of an appropriate model to study the delivery approach; selection of an effective targeting agent; optimization of the number of targeting agents per nanoparticle; availability of free reactive area on the particle surface that may initiate non-specific binding; ability of the targeting agent to sequester the target and hydrodynamic size of the nanoconjugates.