During the MICREAgents project much progress has been made towards lablet docking in work of RUG and HUJI. It was demonstrated that polymeric hydrogels with DNA incorporated into the network architecture can be selectively connected to each other with the help of base pairing. Therefore, separate hydrogel blocks with dimensions of millimeter were prepared, which contain complementary DNA sequences covalently attached to the network structure (shown in red and blue). Upon mixing of these macroscopic objects in aqueous environment, the cubes attach to each other once they get in contact. The gel blocks can be disassembled by heating the solution above the melting temperature of the oligonucleotides and shaking. Similar results were achieved with objects of smaller size in the range of micrometer. Polymeric supports with dimensions of 100 x 100 μm were covered with a thin gold layer. Atop of the metal, a coating of DNA was installed employing rolling circle amplification. Two sequences were designed in such a way that they can hybridize to each other at neutral pH, while at pH of 5 one sequence forms an i-motif, which leads to dehybridization. With these nucleic acid surface coatings, the micron-sized objects could be assembled and disassembled reversibly by varying the pH between neutral and acidic successfully demonstrating that the self-assembly of microstructures can also be controlled via sequence specific base pairing.
Figure 1 Polyacrylamide DNA hydrogels stained with Rhodamine 6G (a) and Coomassie brilliant blue (b). The hybridization of blue and red gel blocks is mediated by sequence specific Watson-Crick base pairing (c). (RUG)
Figure 2 Self-assembly of microscopic objects mediated by DNA. The equilibrium between the G-quadruplex (i-motif) and the double-stranded configurations can be controlled by pH, which allows for the reversible association and dissociation of objects with complementary sequences. (HUJI)