Silica nanoparticles modified with aminosilanes as carriers for plasmid DNA

We synthesised silica nanoparticles (SiNP) with covalently linked cationic surface modifications and demonstrated their ability to electrostatically b ind, condense and protect plasmid DNA. These particles might be utilised as DNA carriers for gene delivery. All nanoparticles were sized between 10 an d 100 nm and displayed surface charge potentials from +7 to +31 mV at pH 7. 4. They were produced by modification of commercially available (IPAST) or in-house synthesised silica particles with either N-(2-aminoethyl)-3-aminop ropyltrimethoxysilane or N-(6-aminohexyl)-3-aminopropyltrimethoxysilane. Ai l particles formed complexes with pCMVbeta plasmid DNA as evidenced by rati o dependend retardation of DNA in the agarosegel and co-sedimentation of so luble DNA with nanoparticles. High salt and alkaline pH did inhibit complex formation. Absorption onto the particles also decreased the hydrodynamic d imensions of plasmid DNA as shown by photon correlation spectroscopy. Compl exes formed in water at a w/w ratio of Si26H:DNA (pCMVbeta) of 300 were sma llest with a mean hydrodynamic diameter of 83 nm. For effective condensatio n a w/w ratio of Si26H:DNA of 30 was sufficient. Further, the absorbed DNA was protected from enzymatic degradation by DNase I. (C) 2000 Elsevier Scie nce B.V. All rights reserved.