Synthesis of Nitric Oxide-Releasing Silica Nanoparticles

Abstract

The synthesis and characterization of a new nitric oxide (NO)-releasing scaffold prepared from\namine-functionalized silica nanoparticles are reported. Inorganic−organic hybrid silica was prepared via\ncocondensation of tetraethoxy- or tetramethoxysilane (TEOS or TMOS) and aminoalkoxysilane with\nappropriate amounts of ethanol (or methanol), water, and ammonia. The amine functional groups in the\nsilica were converted to <i>N</i>-diazeniumdiolate NO donors via exposure to high pressures of NO (5 atm)\nunder basic conditions. Control over both the structure and concentration of the silane precursors (i.e.,\ntetraalkoxy- and aminoalkoxysilanes) and specific synthetic conditions allowed for the preparation of NO\ndonor silica particles of widely varying sizes (<i>d</i> = 20−500 nm), NO payloads (50−1780 nmol·mg^-1),\nmaximum amounts of NO released (10−5500 ppb·mg^-1), half-lives (0.1−12 h), and NO release durations\n(up to 30 h). The silica nanoparticles were characterized by solid-state ²⁹Si nuclear magnetic resonance\n(NMR), atomic force microscopy (AFM), elemental analysis, and gas adsorption−desorption isotherms.\nThe advantages of silica-derived NO storage/delivery systems over previously reported macromolecular\nNO donors include the ability to (1) store large quantities of NO, (2) modulate NO release kinetics, and (3)\nreadily tune particle size based on the composition of the particle. In addition, a one-pot strategy for preparing\nthe NO donor silica allows for straightforward, high-throughput synthesis and purification.