Macroporous, responsive DNA cryogel beads

Biocompatible soft materials that are macroporous and tough are in demand for a range of applications. Here, we describe the preparation of macroporous DNA cryogel beads by crosslinking DNA in frozen aqueous solution droplets at −18 °C. Ethylene glycol diglycidyl ether was used as the crosslinker and N,N,N′,N′-tetramethylethylenediamine as catalyst. The beads swell in 4.0 mM NaBr 74–212 times their dry weights and exhibit moduli of elasticity around 0.5 kPa. In dry state, they contain irregular large pores of 10 1–10 2 μm in sizes due to the ice crystals acting as a template during the gelation reactions. DNA beads can be compressed up to about 80% strain without any crack developments. They also exhibit reversible swelling–deswelling cycles in water and acetone, respectively, undergoing a discrete phase transition in aqueous acetone solutions containing 51% acetone. The ability of the beads for the removal of carcinogenic agents from aqueous solutions was also demonstrated using phenanthrene as a model compound. The sorption capacity of the beads was found to be 420 μg phenanthrene/g DNA.