Figure 1 shows hydrogel-aptamer capture and release. The hydrogel can be made sensitive to environmental variables. In the current study, changes in solution pH cause the hydrogel to either swell or contract. High pH produces a swollen state, causing slender probes or aptamers (seen in blue) to extend, like the claws of a kitten.
These aptamers, (short DNA, RNA or peptide molecules sensitive to specific chemical targets), extend into a mixed solution in an upper compartment of the device, exposing them to the molecules with which they bind.
When the pH of the hydrogel is reduced and the environment becomes acidic, the hydrogel contracts, causing the aptamer probes to relax, pulling away the bound molecules (orange and yellow), which are released and free to re-circulate.