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 ¹-10² 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.