Stimuli‐Responsive Peptide Self‐Assembly to Construct Hydrogels with Actuation and Shape Memory Behaviors

Abstract

Hydrogel actuators, capable of generating reversible deformation in response to external stimulus, are widely considered as new emerging intelligent materials for applications in soft robots, smart sensors, artificial muscles, and so on. Peptide self‐assembly is widely applied in the construction of intelligent hydrogel materials due to their excellent stimulus response. However, hydrogel actuators based on peptide self‐assembly are rarely reported and explored. In this study, a pH‐responsive peptide (MA‐FIID) is designed and introduced into a poly(N‐isopropyl acrylamide) backbone (PNIPAM) to construct bilayer and heterogeneous hydrogel actuators based on the assembly and disassembly of peptide molecules under different pH conditions. These peptide‐containing hydrogel actuators can perform controllable bending, bucking, and complex deformation under pH stimulation. Meanwhile, the Hofmeister effect of PNIPAM hydrogels endows these peptide‐containing hydrogels with enhanced mechanical strength, ionic stimulus response (CaCl2), and excellent shape‐memory property. This work broadens the application of supramolecular self‐assembly in the construction of intelligent hydrogels, and also provides new inspirations for peptide self‐assembly to construct smart materials.

Stimuli-responsive peptide hydrogels for biomedical applications

“…3e). 67 The FIID sequence can self-assemble at neutral pH by non-covalent interactions such as hydrophobic interaction, hydrogen bonding, and π–π stacking, and aspartic acid deprotonation when pH decreases weakens the aggregation effect and depolymerizes the gel. By harnessing the assembly of peptide molecules in varying pH environments, they successfully fabricated bilayer and heterogeneous hydrogel actuators.…”

3D shape morphing of stimuli-responsive composite hydrogels

“…The ionic copolymer layer can gradually reswell and attain to a greater expansion compare to the swelling of the pure PNIPAM layer, which means the bilayer structure can be flat and even oppositely bend. 358 Moreover, to realize the complicate shape morphing and multifunctionalities, integrating hydrogels with different responsiveness or various functions is attractive. Inspired by the metamorphosis development of bioluminescent octopuses, Wang et al combined the temperature-responsive hydrogel, the pH-responsive hydrogel, and the redlight-emitting Eu 3+ coordinated hydrogel (Eu-gel) to construct a hydrogel actuator enabling to execute origami-like 3D shape morphing and information encryptions (Fig.…”

Thermal and Near-Infrared Light-Responsive Hydrogel Actuators with Spatiotemporally Developed Polypyrrole Patterns

“…The existence of water molecules endows reversible volume change through the interdiffusion of water molecules with the environment. Therefore, introducing component or structural anisotropies to differentiate the amplitude and speed of volume change are general routes for the development of hydrogel actuators. − Of them, surface patterning strategies are commonly adopted to facially and effectively alter hydrogel volume-changing related properties. − However, most of them rely on the diffusion of active substances from the surface into the hydrogel network, which is usually realized by direct contact of reactive solutions with the hydrogel. − The implementation is usually cumbersome and time-consuming; the precision of the resulting patterns is relatively low, and therefore, the actuating behaviors determined by the patterns are also simple. The above-mentioned drawbacks hinder the better biomimicry of natural creatures capable of exhibiting intricate deformations.…”