Abstracts

Metallic nanoparticles involve metallic atoms arranged in a way that distinct and very interesting characteristics, such as specific electronic structure (local density of states) and quantum confinement properties, will appear, enabling their use in the most varied applications, from drug delivery systems to membrane markers. The development of biomaterials based on metallic nanoparticles for makes it possible to combine the properties of the biomolecule of interest with properties of the nanoparticles, going from modifications in thermal and mechanical characteristics (when incorporated into polymeric matrices), up to changes in the aggregation states, photophysical properties, biocompatibility, non-toxicity, and transport of molecules of interest for controlled release. However, for these devices to be efficient, it is essential that the development of biomaterials is carried out in such a way that neither the nanoparticle manufacturing processes nor the strategies for incorporating the biomolecule of interest are capable of promoting structural changes in such a way as to compromise their effectiveness. Thus, the success of developing advanced biomaterials depends on conformational studies of the molecules of interest that will be incorporated into the nanoparticles, considering physicochemical changes that the preparation processes may cause in their surroundings. In this sense, we have been working on the photophysical characterization, using photoluminescence (PL) and photoluminescence excitation (PLE), of the interactions between gold nanoparticles synthesized with poly(ethylene glycol) dithiol 8000, PEG(SH)₂AuNP, and the lipid phosphatidylserine labelled with NBD (N-(7-nitro-2- 1,3-benzoxadiazol-4-yl) in three different positions: 18:1, 18:6 and 18:12. We will discuss the conformation and aggregation of NBD in several concentrations and the changes in NBD conformation when the PEG(SH)₂AuNP are titrated into NBD solution. In a nutshell, our results showed, so far, that microenvironment of the polar heads undergo the same changes whether in buffer or in nanoparticle solution, suggesting that the NBD- PEG(SH)₂AuNP interaction is through the nonpolar tails and not the polar heads.