DNA-Chitosan Hydrogels: Formation, Properties, and Functionalization with Catalytic Nanoparticles

DNA-chitosan (DNA-CS) hydrogels were prepared on the basis of interpolyelectrolyte complexes (IPEC) in a co-assembled regime by in situ charging of the polysaccharide in a DNA solution. In contrast to poorly controlled coacervates formed upon mixing of DNA and CS solutions, stable DNA-CS IPEC hydrogels are formed at near-stoichiometric ratios of DNA and chitosan ionogenic groups. Structure, stability, and ion absorption properties of such hydrogels depended strongly on the ratio between cationic (CS) and anionic (DNA) counterparts in hydrogels. Abundant amino- and nitrogen-containing aromatic groups of co-assembled DNA and CS make their hydrogel an efficient, multitarget absorbent toward metal ions. Such strong affinity of both DNA and CS to Au³⁺ cation was used to entrap Au³⁺ ions into the DNA-CS hydrogels. Subsequent reduction of Au³⁺ ion inside hydrogels resulted in the formation of ∼2-3 nm size Au nanoparticles on DNA-CS scaffolds. Metallized hydrogels demonstrated catalytic activity in reduction of various nitroaromatics that depended on the ratio between CS and DNA in the hydrogel.