Freezing-Assisted Conjugation of Unmodified Diblock DNA to Hydrogel Nanoparticles and Monoliths for DNA and Hg Sensing.

Acrydite-modified DNA is the most frequently used reagent to prepare DNA-functionalized hydrogels. Herein, we show that unmodified penta-adenine (A ) can reach up to 75 % conjugation efficiency in 8 h under a freezing polymerization condition in polyacrylamide hydrogels. DNA incorporation efficiency was reduced by forming duplex or other folded structures and by removing the freezing condition. By designing diblock DNA containing an A block, various functional DNA sequences were attached. Such hydrogels were designed for ultrasensitive DNA hybridization and Hg detection, with detection limits of 50 pM and 10 nM, respectively, demonstrating the feasibility of using unmodified DNA to replace acrydite-DNA. The same method worked for both gel nanoparticles and monoliths. This work revealed interesting reaction products by exploiting freezing and has provided a cost-effective way to attach DNA to hydrogels.