Highly expansive DNA hydrogel films prepared with photocrosslinkable poly(vinyl alcohol)

Deoxyribonucleic acid (DNA) has a lot of characteristic features, e.g., anionic polyelectrolyte, molecular recognition and condensed π electron. Therefore, it is expected to be applied as functional materials in not only biological but also physical fields. In this report, we attempted to prepare water-insoluble DNA films by mixing DNA and photolinkable polymer, aiming at the fabrication of bio-functionalized hydrogel films. For this purpose, photocrosslinkable polyvinyl alcohol (azide-unit pendant water-soluble photopolymer; AWP) was used. An aqueous DNA and AWP mixture was cast onto glass substrates. Irradiation of UV light on it for certain minutes provided a hydrogel film by photocrosslinking between DNA and AWP. When the formed hydrogel film was soaked in pure water for 1 day, large expansion of the film was observed. The expanded film was shrunk by soaking it in aqueous NaCl or CTAB solutions. The expansion and shrinkage mechanism of the film was attributed to the penetration of water into the gap between the film and the substrate due to osmotic pressure. This phenomenon can be applied to the fabrication of gel devices, e.g., a novel biosensor and drug delivery system.