Highly Hybtidizable Spherical Nucleic Acids By Glutathione Treatment And Polythymine Spacing

Gold nanoparticle-(AuNPs) templated spherical nucleic acids (SNAs) have been demonstrated as an important functional material in bionanotechnology. Fabrication of SNAs having high hybridization capacity to their complementary sequences is critical to ensure their applicability in areas such as antisense gene therapy and cellular sensing. The traditional salt-aging procedure is effective but tedious, requiring 1-3 days to complete. The rapid low-pH assisted protocol is efficient, but causes concerns related to nonspecific DNA adsorption to the AuNP core. To address these issue, we systematically compared the SNAs prepared by these two methods (salt-aging method and low-pH protocol). In terms of the number of complementary DNA that each SNA can bind and the average binding affinity of each thiolated DNA probe towards its complementary strand, both method yielded comparable hybridizability, although higher loading capacility was witnessed with SNAs made using the low-pH method. Additionally, it was found that the nonspecific DNA binding could be eliminated almost completely by a simple glutathione (GSH) treatment of SNAs. Compared to the conventional methods using toxic mercapto-hexanol or alkanethiols to remove nonspecific DNA adsorption, glutathione is biocompatible, mild, cost-effective, and technically easy to use. Moreover, rational design by inclusion of a poly-thymine spacer into the DNA sequences resulted in enhanced DNA loading capacity and stability against salt-induced aggregation. This work provides not only efficient and simple technical solutions to the issue of nonspecific DNA adsorption, but also new insights into the hybridizability of SNAs.