CONICET | Buscador de Institutos y Recursos Humanos

ABSTRACT Photoluminescent silicon nanoparticles of 1-2 nm size were synthesized by a wet chemical procedure and derivatized with propylamine (NH2SiNP). Surface NH2 groups were used as linkers for further poly (ethylene glycol) and folic acid attachment (PEG-NHSiNP and Fo-NHSiNP, respectively) in order to provide the particles with efficient targeting to tumors and inflammatory sites. The particles were characterized by TEM, FTIR, XPS,  potential, DLS, and time-resolved anisotropy. The photophysical properties, photosensitizing capacity, and interaction with proteins were observed to depend on the nature of the attached molecules. While PEG attachment to NH2SiNP did not change the particles photophysical behavior, attached folic acid diminished the particles photoluminescence. Despite all the particles retained the capacity for 1O2 generation, the efficient 1O2 quenching by the attached surface groups might be a drawback when using these particles as photosensitizers of 1O2. In addition, attached folic acid provided the particles with the capacity of superoxide radical anion, O2.-, generation. The particles were capable of binding to bovine serum albumin (BSA) within quenching distances to tryptophan residues. NH2SiNP and PEG-NHSiNP ground state complexes with BSA showed binding constants of (3.1 ± 0.3)104 and (1.3+/-0.4)X103 M-1, respectively. The lower value observed for PEG-NHSiNP complexes indicates that surface PEGylation effectively leads to a reduction in protein absorption, as required for opsonization prevention. An increase in the particles luminescence upon binding to BSA was observed and attributed to the hydrophobic environment provided by the protein. In addition, NH2SiNP-BSA complexes also showed capacity for resonance energy transfer.