The development of small (40-150nm) nanoparticles is of significant interest in biomedicine for effective detection and delivery of therapeutic molecules to diseased cells. The optical exploration of hollow gold nanoshells with sacrificial Co cores reveals the spectral FWHM increases due to the presence of Co while only minimally altering the spectral mean wavelength position. Other plasmon resonant nanostructures including nanoshells and nanomatryoshkas are valuable delivery and imaging vectors for oligonucleotide based therapies. In this study, light-triggered release of siRNA hybridized to a polypeptide functionalized NS is employed for gene silencing therapy of a specific pathogenic gene transcript with the intent to downregulate proteins. Similarly, fluorescently labeled NM are conjugated with an ESTA-1 aptamer via for bioimaging of highly specific inflammation targeting at metastasis sites. Each having advantageous platforms of ideal size, therapeutic gene optimization and heightened metastasis targeting, these three nanostructures prove viable functionality in cancer theranostics.