Novel Synthesis of potential Nanostructures for Photodynamic Therapy

P. F. GARCIA; L. PEREZ; E. CORONADO; G. A. ARGÜELLO

Córdoba Capital

Congreso; 16th International Conference of Photobiology; 2014

Photodynamic Therapy involves the presence of a drug capable to generate damage to tumoral cellsin presence of visible light. In this sense Nanoparticles (NPs) have been deeply studied because of thehigh absorption in the visible range. In this work, we present the synthesis of nanoparticles functionalizedwith tris(5-NH2-phenanthroline) ruthenium (II) complex. This functionalization leads to a controlledformation of dimers. Dimers could be very effective for generating photothermal damage because theexcitation of the surface plasmon resonance (SPR) results in a temperature increase near the NP surface.In addition they present the advantage that the frequency of the SPR resonance can be tuned by usingdifferent NPs sizes or interparticle separations.The surface enhanced Raman scattering (SERS) response of the complex located in the gap ofthe NP aggregates results in an analytical SERS enhancement factor of 10 5. This feature corroboratesthat the ruthenium complex is indeed located between nanoparticles. An additional confirmation of thisfact has been performed using Transmission Electron Microscopy (TEM), in which dimers, trimers andother aggregates where found.A kinetic study of the NP aggregation process, followed by the evolution of the UV Vis extinctionspectra, has been also performed. The results shows that there are three different stages: an inductionperiod where the population of isolated NP is the most important but it starts to decrease very slowly, asecond stage in which small NP aggregate such as dimers an trimers are the dominant populations and afinal stage in which we can appreciate de formation of NP ―chains‖.The photophysics of this system was further investigated by performing fluorescence quenchingexperiments, finding Stern Volmer constants around Ksv=4x1011 M-1. These constants involved aphenomenon called superquenching, which is a very efficient electron transfer process between thequencher and the fluorophore.