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Sol-gel synthesis of dna encapsulated silica

Kapusuz, Derya
Sol-gel processing routes for encapsulation of double stranded DNA in solid porous silica hosts have been established. The encapsulation was carried out in two steps: hydrolysis of a silica-forming alkoxide-based sol was followed by condensation/gelation to a solid form upon addition of a buffer solution containing DNA molecules. The effects of gelation chemistry and DNA amount on chemical and microstructural properties of resultant silica matrices and on DNA encapsulation efficiency were investigated. The analytical characterization was performed by UV-vis spectroscopy, 29Si nuclear magnetic resonance spectroscopy and by nitrogen adsorption studies. It was demonstrated that DNA incorporation had a pH-dependent catalytic effect on gelation kinetics and promoted silica network completion. In addition, the scale of porosity and the average pore size of the resultant silica increased with gelation pH and also with DNA-buffer solution in the starting sol-gel formulation. The chemistry-derived pore size variation controls the DNA encapsulation efficiency in the silica matrices and the DNA holding capacity strongly depends on the scale of the porosity attained. The selective adsorption of ethidium bromide- a DNA-intercalative reagent molecule- on DNA-silica gels confirmed that the DNA molecules remained entrapped within the silica host in their native state without any deterioration. Besides pure silica, amine-functionalized hybrid silica hosts were also formed by sol-gel. The hybrid gels were found not to be suitable for DNA encapsulation, as these matrices dissolve in aqueous environment due to incomplete silica network formation. The DNA-doped silica hosts may provide promising matrices for development of biosensors, bioreactors and bioassay platforms.