DNA sequence–directed shape change of photopatterned hydrogels via high-degree swelling

Abstract

Shape-changing hydrogels that can bend, twist, or actuate in response to external stimuli are critical to soft robots, programmable matter, and smart medicine. Shape change in hydrogels has been induced by global cues, including temperature, light, or pH. Here we demonstrate that specific DNA molecules can induce 100-fold volumetric hydrogel expansion by successive extension of cross-links. We photopattern up to centimeter-sized gels containing multiple domains that undergo different shape changes in response to different DNA sequences. Experiments and simulations suggest a simple design rule for controlled shape change. Because DNA molecules can be coupled to molecular sensors, amplifiers, and logic circuits, this strategy introduces the possibility of building soft devices that respond to diverse biochemical inputs and autonomously implement chemical control programs.

A Single Extracellular Vesicle (EV) Flow Cytometry Approach to Reveal EV Heterogeneity

“…This technique employs conformation-switchable DNA probe to bind to the EV surface marker, which triggers the engineering of a DNA nanostructure by hybridization chain reaction (HCR). [11] The HCR products not only enlarge the overall size of the single EV to be beyond 500 nm, but also can bind to multiple fluorophores to amplify the signal from the few marker molecules locating on the limited area of EV surface, both enabling visualization of single EVs in a conventional flow cytometer, and greatly simplifying measurement of multiple markers on the same EV.…”

Sequentially Controlled Deformations of Patterned Hydrogels into 3D Configurations with Multilevel Structures

“…Scientists have developed bioinspired systems with through‐thickness and/or in‐plane gradient structures to realize typical deformations, including bending, folding, and twisting . Reversible shape transformations or step‐by‐step deformations can be realized by incorporating different responsive polymers into one composite hydrogel . For example, Cangialosi and coworkers have patterned DNA‐cross‐linked hydrogels with multiple domains that exhibited different shape changes in response to different hairpin inputs that altered the swelling capacities of specific hydrogels .…”

“…Reversible shape transformations or step‐by‐step deformations can be realized by incorporating different responsive polymers into one composite hydrogel . For example, Cangialosi and coworkers have patterned DNA‐cross‐linked hydrogels with multiple domains that exhibited different shape changes in response to different hairpin inputs that altered the swelling capacities of specific hydrogels . As a consequence, step‐by‐step deformations were triggered by sequential stimulations.…”

Site‐Specific Pre‐Swelling‐Directed Morphing Structures of Patterned Hydrogels

“…[19] By using photolithography,m ore complex distributions of components and internal stresses can be encoded in the planar-patterned hydrogels,leading to various 3D configurations under external stimuli. [25][26][27][28][29][30][31] Specifically,t he combination of bending and folding by creating throughthickness gradients has been intensively investigated to form elaborate configurations,e nabling encapsulation or handling of objects. [15,24] More complex configurations can be obtained by stacking individual structures of typical forms,each responsible for one mode of deformation in the integrated system, such as localized bending, folding,a nd twisting.…”

“…[39,40] For example,w eprepared square or round loop patterned with high-swelling discs (Figures 4b(i)a nd Figure 4c(i));t he free-swelling (without the pre-swelling step) led to deformation of patterned gels into af our-pointed star and cauliflower-like configurations (Figures 4b-(ii)a nd Figure 4c(ii)), respectively,i n which all domes buckled in the same direction yet constrained by the corner or central non-swelling gels.H owever, selectively pre-swelling led to localized buckling into opposite directions and thus the formation of desired configurations,s uch as the dumbbell-like and cloverleaf-like shapes (Figures 4b(iii) and Figure 4c(iii)). [9,22,30] In conclusion, we have demonstrated af acile,v ersatile strategy to control the morphing structures of patterned hydrogels via as ite-specific pre-swelling step.T he selective pre-swelling of hydrogel induced at ransient through-thickness gradient and therefore resulted in buckling in the desired direction. Them odeled behaviors of patterned hydrogels consisted well with the experimental observations.W e should note that the predefined overall pattern has ad etermining influence on the swelling-induced shape change of the hydrogel as aresult of the geometric confinement.…”