Versatile Synthesis of Thiol- and Amine-BifunctionalizedSilica Nanoparticles Based on the Ouzo Effect.

In this article, we report a novel,nanoprecipitation-based methodfor preparing silica nanoparticles with thiol and amine cofunctionalization.(3-Mercaptopropyl)trimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane(APTMS) were used as the organosilane precursors, which were subjectedto acid-catalyzed polycondensation in an organic phase containinga water-miscible solvent (e.g., dimethyl sulfoxide). A pale colloidalsolution could be immediately formed when the preincubated organicphase was directly injected into water. The initial composition ratiobetween MPTMS and APTMS is an important factor governing the formationof nanoparticles. Specifically, large, unstable micrometer-sized particleswere formed for preparation using MPTMS as the sole silane source.In contrast, when APTMS was used alone, no particles could be formed.By reducing the fraction of APTMS (or increasing that of MPTMS) inthe initial mixture of organosilanes, the formation of nanometer-sizedparticles occurred at a critical fraction of APTMS (i.e., 25%). Remarkably,a tiny fraction (e.g., 1%) of APTMS was sufficient to produce stablenanoparticles with a hydrodynamic diameter of about 200 nm. Otherfactors that would also affect particle formation were determined.Moreover, an interesting temperature effect on particle formationwas observed. The TEM micrographs show spherical nanospheres withmean sizes of 130–150 nm in diameter. The solid-state 29Si NMR spectra demonstrate that the hybrid silica materialscontain fully and partially condensed silicon structures. The bifunctionalizedsilica nanoparticles have positive zeta potentials whose magnitudesare positively correlated with the amount of APTMS. The total thiolcontent, however, is negatively correlated with the amount of APTMS.The cationic nanoparticles can bind an antisense oligonucleotide ina composition-dependent manner. [ABSTRACT FROM AUTHOR]