A biological strategy for fabrication of Au/EGFP nanoparticle conjugates retaining bioactivity

Recently, it has been found that thiolated oligonucleotides can be used to direct the assembly of gold colloids into ordered functional nanostructures. However, approaches for fabricating Au/DNA conjugates by using a linear, functional, double-stranded (ds) DNA fragment that directly binds to a Au NP surface have not been reported. In this paper, we used a ligase-dependent strategy to synthesize a 1.7 kb, thiolated dsDNA fragment and generated novel nanocrystals by coupling it to 13 nm Au NPs. The conjugates contained Au/EGFP with EGFP/ Au molar ratios of 1:1, 2:1, and 3:1, as determined by their electrophoretic mobility and AFM imaging. The Au/EGFP nanoconjugates could still be digested by restriction endonuclease (RE) and expressed as functional proteins in mammalian cells, indicating the biological activities of DNA fragments were retained after conjugation with Au NPs. This biological strategy for fabrication of Au/DNA conjugates may be applied to molecular imaging, nanomedicine, and nanobiosensor technology.