Abstract
DNA-chitosan (DNA-CS) hydrogel was prepared by in situ complexation between oppositely charged DNA and chitosan polyelectrolytes via electrostatic cross-linking to study its adsorption characteristics. The DNA-chitosan hydrogel matrix contains (i) cationic (NH(3)(+)) and anionic (PO(4)(-)) sites for electrostatic binding with ionic species, (ii) -OH and -NH(2) groups and heteroaromatic DNA nucleobases for chelation of heavy metal ions, and (iii) DNA double-helix for recognition and binding to small organic molecules of various structures and polarities. DNA-CS hydrogels efficiently bind with Hg(2+), Pb(2+), Cd(2+), and Cu(2+) metal cations of significant environmental concern. Adsorption capacities of DNA-CS hydrogels for studied metal ions depend on hydrogel composition and pH of solution and reach ca. 50 mg/g at neutral pHs. Hydrogels with higher DNA contents show better adsorption characteristics and notably higher adsorption capacity to Hg(2+) ions. Because of the co-existence of cationic and anionic macromolecules in the DNA-CS hydrogel, it demonstrates an affinity to both anionic (Congo Red) and cationic (Methylene Blue) dyes with moderate adsorption capacities of 12.6 mg/g and 29.0 mg/g, respectively. DNA-CS hydrogel can also be used for adsorptive removal of pharmaceuticals on conditions that their molecules are sufficiently hydrophobic and have ionogenic group(s). Facile preparation and multitarget adsorption characteristics of DNA-CS hydrogel coupled with sustainable and environmentally friendly characteristics render this system promising for environmental cleaning applications.