DNA motifs hydrogel microparticles as gold nanocatalyst support material

Gold nanoparticles (Au NPs) are unique catalysts because the nanoparticulation increases the number high coordination unsaturation sites. For Au NPs to act as catalysts, the choice of a suitable support for the desired reaction is essential to ensure homogeneous dispersion of the particles while maintaining their nanosize. As a support material, hydrogels obtained by three-dimensional crosslinking of hydrophilic polymers are suitable dispersants for Au NPs. In addition, their high affinity for water-rich environments and high biocompatibility have attracted attention for biological and biomedical reactions. However, application in small, confined spaces such as in vivo requires micronization of the hydrogel. Here, we have developed a gold catalyst supported on micro-sized DNA hydrogels with variable internal crosslinking densities composed of simple DNA nanostructures called motifs. The short strand length of the DNA motif resulted in DNA hydrogel particles with high crosslinking density and Au NPs with small particle size. Furthermore, our micro-sized DNA hydrogel particle-supported gold catalyst system sufficiently advanced the model reaction with a very small amount of gold catalyst compared to a gel-supported gold catalyst system with a comparable Au NP size. The crosslinking density of the DNA hydrogel particles, and thus the size of the resulting Au NPs, can be easily varied and the catalytic activity can be enhanced by increasing the surface area of the hydrogel catalyst support through microparticulation. Our findings based on DNA nanotechnology suggest that the physical properties of the DNA hydrogel particles, such as particle size and crosslinking density, and the catalytic activity of the Au NPs, can be easily designed using computer software, as can the arrangement and length of the motifs that form the constituent units.