Star‐Polymer–DNA Gels Showing Highly Predictable and Tunable Mechanical Responses

Abstract

Dynamically crosslinked gels are appealing materials for applications that require timedependent mechanical responses. DNA duplexes are ideal crosslinkers for building such gels because of their excellent sequence addressability and flexible tunability in bond energy.However, the mechanical responses of most DNA gels are complicated and unpredictable despite the high potential of DNA. Here, we demonstrate a DNA gel with a highly homogeneous gel network and well-predictable mechanical behaviors by using a pair of starpolymer-DNA precursors with presimulated DNA sequences showing the two-state transition.The melting curve analysis of the DNA gels reveals the good correspondence between the thermodynamic potentials of the DNA crosslinkers and the presimulated values by DNA calculators. Stress-relaxation tests and dissociation kinetics measurements show that the macroscopic relaxation time of the DNA gels is approximately equal to the lifetime of the DNA crosslinkers over four orders of magnitude from 0.1-2,000 sec. Furthermore, a series of durability tests find the DNA gels are hysteresis-less and self-healable after the applications of repeated temperature and mechanical stimuli. These results demonstrate the great potential of star-polymer-DNA precursors for building gels with predictable and tunable viscoelastic properties, suitable for applications such as stress-response extracellular matrices, injectable solids, and soft robotics.

Network Percolation in Transient Polymer Networks with Temporal Hierarchy of Energy Dissipation

“…This work aims to provide a theoretical basis for the prediction of network percolation and rheology in metallo-supramolecular polymer networks including complexes with various coordination geometries. This issue becomes relevant in many of the applications of transient hydrogels, specifically the ones that require a temporal hierarchy of relaxation modes. ,, The theoretical basis includes an extended Miller–Macosko’s model that correlates the network composition to the connectivity and a thermodynamic model that predicts the complex composition in the two-metal ion transient network, as described in Section and illustrated in Figure b. To challenge this model with experiments, where the coordination geometry and, therefore, the complex composition change effectively, we form model-type networks based on the coordination of tetraEPh polymer precursors with a mixture of divalent transition metal ions.…”

Dynamic matrices with DNA-encoded viscoelasticity for advanced cell and organoid culture

“…Moreover, a DNA-crosslinked hydrogel had been shown to exhibit temperature-dependent stress-relaxation. In cell culture, however, temperature cannot be altered at will, and the effects of chemical matrix modifications on cell development can be difficult to disentangle from pure stress relaxation effects 61 . With the help of SRCs, for the first time the stress relaxation of a material can be adjusted systematically over 3 orders of magnitude by altering merely a few nucleobases on the DNA crosslinker sequence.…”

“…Previous studies had demonstrated control over stress relaxation via chemical modifications to the polymer scaffold or side groups 26,[62][63][64][65][66] . Moreover, a DNA-crosslinked hydrogel had been shown to exhibit temperature-dependent stress-relaxation 67 . In cell culture, however, temperature cannot be altered at will, and the effects of chemical matrix modifications on cell development can be difficult to disentangle from pure stress relaxation effects.…”

Connectivity Defects in Metallo-Supramolecular Polymer Networks at Different Self-Sorting Regimes

“…This includes the majority of reversible covalent bonds, whose stability can be adjusted using external catalysts or stimuli. , A prime example is the hydrazone bond formed between aldehyde and hydrazine groups, whose dissociation rate can be tuned over two orders of magnitude using aniline as the catalyst . In the same way, the dissociation of boronic ester bonds formed between boronic acid and diols strongly depends on and can be tuned by pH and temperature. − Alternately, leveraging the combination of hydrophobic and electrostatic interactions, polymer precursors functionalized with heterocomplementary macrocycles and various guests are reported to form transient hydrogels with a stability that is tunable in more than five orders of magnitude. , Similarly, heterocomplementary hydrogen bonding groups are used to suppress the macroscopic phase separation between immiscible polymer precursors, but their utility in hydrogel formation is normally limited due to the competition with water. , In contrast, Sakai and co-workers have recently formed transient hydrogels using tetraPEG precursors grafted with DNA sequences, which form heterocomplementary duplexes mediated through hydrogen bonds . The stability of hydrogels could be continuously tuned by varying the composition and length of DNA segments.…”