Synthesis of DNA-encapsulated silica elaborated by sol–gel routes

The highly specific functions of DNA can be used for designing novel functional materials. However, aqueous solubility and biochemical instability of DNA impede its direct utilization as a functional component. Herein, preparation of a hybrid material encapsulating the DNA molecules (double-stranded salmon sperm, 50–5000 base pairs) in robust host—sol–gel-derived silica—has been described. The encapsulation was carried out in two steps: hydrolysis of an acidic tetraethylorthosilicate [Si(OC2H5)4] sol and was followed by condensation near physiological pH upon addition of alkaline DNA-containing solutions. The gelation behavior and structural properties of the DNA–silica hybrids were investigated by29Si nuclear magnetic resonance and by nitrogen adsorption. The selective adsorption of a DNA-interactive reagent molecule (ethidium bromide) in their diluted aqueous solutions on DNA–silica hybrids confirmed that the DNA molecules remained entrapped within the silica host without any deterioration. A DNA encapsulation mechanism correlating the silica microstructure and DNA holding efficiency has been proposed.