Wenting Zhao, Bioengineering Graduate Program (BIEN), Hong Kong University of Science and Technology, Clear Water Bay,, Kowloon, Hong Kong, Thomas Ming-Hung Lee, Department of Chemical Engineering, Hong Kong University of Science and Technology, Clear Water Bay,, Kowloon, Hong Kong, and I.-Ming Hsing, Department of Chemical Engineering and Bioengineering Postgraduate Program, Hong Kong University of Science and Technology, Clear Water Bay,, Kowloon, Hong Kong.
Gold nano-particles have been proven to be promising both for biological diagnostics and for bionanotechnology. However, there is an inevitable issue when modifying them with biomolecules (such as thiolated DNA) that unprotected bare gold nano-particles are vulnerable to salt-induced aggregation. Considering this, the conventional synthesis process of widely used DNA-gold nano-particles conjugate is very time-consuming, which includes the incubating of thiolated DNA and bare gold nano-particles over night under very low salt condition and then adding salt gradually followed by aging for around 40 hours. In this study, we report the use of mononucleotides to stabilize the gold nano-particles in salt solution, the adsorption of which occurs instantaneously and appears to be temperature dependent. In connection to a temperature controlled exchange of mononucleotides and thiolated DNA, the time for DNA-gold conjugates synthesis can be remarkably saved. The underlying principle of the present approach is based on our new findings that the binding of mononucleotides (dNTPs) and oligonucleotides to gold nano-particles is temperature dependent. At room temperature, when a mixture of dNTPs and oligonucleotides are allowed to incubate with the gold nanoparticles, the dNTPs bind much faster than the oligonucleotides and prevent the nanoparticles from immediate salt-induced aggregation. Upon increasing the temperature, dNTPs will be progressively released from particle surfaces and then thiol DNA will bind to the vacant surface left. It seems like thermal control activate the exchange of dNTPs and thiol oligo. After that, the DNA-gold conjugates are formed. Moreover, the salt and relatively higher temperature in this situation will also facilitate the binding of thiol-DNA to gold surfaces. By applying our approach, the overall time of this synthesis process will be dramatically shortened from days to 1 or 2 hours. Furthermore, this temperature dependent approach holds great potential to facilitate many cases where bare gold nano-particle involved.