A study on the PEG-assisted stability of spherical nucleic acid constructed by the freezing method

The freezing method used to prepare DNA-modified gold nanoparticles (SNA) has the advantages of being fast and simple, but the prepared SNA is easy to aggregate. In this paper, the effects of polyethylene glycol (PEG) as an organic macromolecular crowding agent on the single-strand polyadenylate DNA functionalized gold nanoparticles (polyA-SNA) and the single-strand thiolated DNA functionalized gold nanoparticles (HS-SNA) were systematically studied. The experimental results showed the molecular weight and concentration of PEG significantly affect the dispersion and DNA loading of the two kinds of SNA . An increase in DNA strand length inhibits the adsorption of thiolated DNA and polyA-DNA, and the hydrated particle size of SNA increases at first and then decreases with the length of the DNA strand. These phenomena lay on the speculative principle that PEG improved the energy barrier for gold nanoparticles (AuNPs) aggregation through the long chain of macromolecules , and the modification mode and length of surface DNA also play an auxiliary role. This work provided a systematic study and helpful results on improving the stability of SNA prepared by the freezing method.