<title>Optimization of gold nanostructers for laser killing of cancer cells</title>

Abstract

Recently, the first applications of gold nanoshells (Halas and co-workers, 2003), nanospheres and nanosphere clusters (Anderson and co-workers, 2003; Zharov and co-workers, 2003) to the cancer cell diagnostics and laser killing of cancer cells (LKCC) have been reported. However, to be clinically relevant, existing technologies must overcome fundamental problems related with limitations of current understanding the relationship between the nanoparticle/cluster parameters (size, shape, particle/cluster structure, etc.) and the efficiency of LKCC therapy, as well as with limitations of the available methods for synthesis and <i>in situ </i>characterization of new advanced nanoparticles and clusters with unique synergistic properties which are crucial for selective LKCC therapy. Here we report on preliminary simulation results aimed at finding the optimal cluster structures for maximal absorption efficiency of laser radiation. We consider also alternative possibilities related with using gold nanorods and nanoshells instead of spherical particles. Two types of nanostructures are studied: (1) bioconjugates of single nanoparticles (spheres, nanoshells, and nanorods); (2); linear chains, 2D lattice arrays, and 3D clusters of gold spheres or conjugates that mimic aggregation of nanoparticles on or within cancer cells. By using the generalized multiparticle Mie solution and different versions of the cluster T-matrix method, we calculated the absorption efficiency of nanostructures under study. The gold nanoshells and nanorods with tunable spectral resonances are shown to be more effective photothermal labels as compared to usual solid gold spheres. In the case of 1D-3D clusters, the interparticle separations and short linear chain fragments are the main structural parameters determining the absorption efficiency