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.