Functionalized branched polysiloxanes with star-branched, comb-branched and dendritic-branched topologies were synthesized. The branched macromolecules were generated by coupling of reactive blocks using a grafting technique (ACS Polym. Prepr. 2001, 42, 227; ACS Symp. Ser. 2003, 838, Chapter 2). The living anionic ring-opening polymerization (ROP) of vinyl-substituted cyclotrisiloxanes (ViMeSiO)3, V3, and, VD2, and the copolymerization of these monomers with hexamethylcyclotrisiloxane, D3, was explored to obtain reactive blocks. Termination of the living polymer, having a lithium silanolate end group, on a reactive core containing SiCl groups led to the grafting of living polysiloxane on the core. Transformation of vinyl groups in the polymer into the reactive SiCl groups by hydrosilylation with Me2HSiCl made possible the grafting of a successive generation of branches. The reactive blocks of high and low density of the precursor vinyl group were obtained by the polymerization of monomers V3 and VD2, respectively. While the homopolymerization led to a uniform density of vinyl groups along the chain, the copolymerization of V3 or VD2 with D3 produced a gradient distribution with the density decreasing in the direction of the chain growth. This arrangement led to a higher density of the vinyl group in the external part of the branched macromolecule. Study of kinetics of the copolymerization of V3 with D3 in THF initiated by BuLi gave the reactivity coefficients k V 3 = 17.8, k D 3 = 0.036 (25 °C), from which the density distribution of vinyl groups in reactive blocks may be determined. Four-arm star copolymers were obtained using (MeCl2SiCH2)2 as the core, whereas the comblike polysiloxane was obtained from a linear copolymer of ViMeSiO and Me2SiO treated with Me2HSiCl. Dendritic polysiloxanes of the first and second generation were obtained using the functionalized starlike polysiloxane as the core.

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Silica nanoparticles have an interesting potential in drug delivery, gene therapy and molecular imaging due to the possibility of tailoring their surface reactivity that can be obtained by surface modification. Despite these potential benefits, there is concern that exposure of humans to certain types of silica nanomaterials may lead to significant adverse health effects. The motivation of this study was to determine the kinetics of cellular binding/uptake of the vinyl- and the aminopropyl/vinyl-modified silica nanoparticles into peripheral blood lymphocytes in vitro, to explore their genotoxic and cytotoxic properties and to compare the biological properties of modified silica nanoparticles with those of the unmodified ones. Size of nanoparticles determined by SEM varied from 10 to 50 nm. The average hydrodynamic diameter and zeta potential also varied from 176.7 nm (+18.16 mV) [aminopropyl/vinyl-modified] and 235.4 nm (-9.49 mV) [vinyl-modified] to 266.3 (-13.32 mV) [unmodified]. Surface-modified silica particles were internalized by lymphocytes with varying efficiency and expressed no cytotoxic nor genotoxic effects, as determined by various methods (cell viability, apoptosis/necrosis, oxidative DNA damage, chromosome aberrations). However, they affected the proliferation of the lymphocytes as indicated by a decrease in mitotic index value and cell cycle progression. In contrast, unmodified silica nanoparticles exhibited cytotoxic and genotoxic properties at high doses as well as interfered with cell cycle.