Engineering an orchestrated release avalanche from hydrogels using DNA-nanotechnology.

Most medical therapies require repeated, sequential administration of therapeutic agents in well-defined intervals and over extended time windows. Typically, the patient is in charge of applying the individual drug doses, and insufficient patient compliance reduces the efficiency of the treatment. Therefore, the development of a smart delivery mechanism releasing therapeutic agents in a pre-defined, time-controlled fashion would be beneficial for many medical treatments. Here, we present a DNA-mediated release cascade which allows for precisely controlling the sequential delivery of several different nanoparticles. By using complementary DNA sequences, nanoparticle aggregates are created, embedded into distinct layers of a hydrogel and released by triggering aggregate dispersal. This mechanism is compatible with physiological conditions as the release cascade is initiated by exposing the nanoparticle-loaded gel to physiological salt concentrations. Moreover, we show that the reservoir hydrogel can be enriched with biopolymers to receive charge-selective release properties towards small molecules - without interfering with the DNA-based release cascade. Owing to the excellent reproducibility, precision and effectiveness of the presented mechanism, a similar DNA-mediated release avalanche may lead to the development of autonomous and robust delivery systems, which minimize the possibility of pharmaceutical therapy failure due to patient non-compliance.