Inducing reversible stiffness changes in DNA-crosslinked gels

Varieties of DNA-based nanodevices have been constructed which undergo stepped configuration changes through the application of single-stranded DNA oligomers. By incorporating such devices in gel networks, new classes of active materials can be devised in which the bulk mechanical properties are controlled by the nanodevices. As a demonstration of this, we report on a DNA- crosslinked gel whose stiffness can be modulated through the application of DNA strands. Each crosslink incorporates a single-stranded region to which a DNA strand with a complementary base sequence, referred to as the fuel strand, can bind, thereby stiffening the crosslink. This changes the tensegrity microstructure of the gel network and stiffens the gel. The gel can be restored to its initial stiffness through the application of the complement of the fuel strand, which clears the fuel strand from the crosslink via competitive binding. Stiffness changes in excess of a factor of three were observed. The ability to switch the mechanical properties of these gels without changing temperature or buffer composition, or other environmental conditions, apart from the application of DNA, makes these materials attractive candidates for use in biotechnology applications.