The aim of this research project is the in vitro assembly of alphaviruses on gold nanoparticle templates to be used as optical probes for specific targeting and cellular imaging. This is the first time that a gold nanoparticle has been used as a template to promote the assembly and growth of an animal virus nucleocapsid. In-vitro assembly of alphavirus nucleocapsids were achieved for various sizes of gold nanoparticles (8-27 nm, core sizes) coupled with nucleic acid. Gold nanoparticles were synthesized and derivatized with a mixture of 48-mer thiol modified ss-DNA and phosphine molecules. These gold conjugates were quantified for DNA on a single nanoparticle by multi-linear regression analysis of the absorption spectra. For instance, we found 550 ± 50 DNAs per gold particle for 11.5nm gold cores. Assembly reactions yielded gold containing alphavirus nucleocapsid-like particles for all different gold sizes. Moreover, to determine the best efficiency of nanoparticle encapsidation we tried the assembly in the presence of controlled and uncontrolled gold surface conditions. We found that unrestrained conditions were more successful in forming artificial cores (67% for 18.7nm cores). These findings suggest that charge neutralization is not sufficient to drive assembly like in the case of non-enveloped viruses. Entropic factors and hydrophobic interactions between the capsid protein and the nucleic acid may also be important. Current research is focused on maximizing the encapsidation efficiency with control of the absorbed DNA molecules on the metallic surface and to establish the structure of the capsid.