Spongelike Porous Silica Nanosheets: From "Soft" Molecular Trapping to DNA Delivery.

Spongelike porous silica nanosheets, with nanometer thicknesses and pores whose diameters are on the hundreds-of-nanometers scale, have been used as a novel carrier for molecular immobilization of different guests. Enhanced properties of encapsulation were shown for drug molecules of different dimensions due to "softness" caused by the specific nanometric features of the porous structure. The encapsulating effect of the structure results in sustained and stimuli-responsive release behavior of immobilized guest molecules. By studying the adsorption process of DNA molecules on spongelike porous nanosheets or on solid nanoparticles by use of a quartz crystal microbalance, we show that better elasticity of surfaces of the porous nanosheets over that of solid nanoparticles can improve the immobilization of guest molecules. The coating of porous silica nanosheets onto various substrates was also found to effectively mediate DNA delivery to mammalian cells.