Hyperexpandable, self-healing macromolecular crystals with integrated polymer networks

Abstract

The formation of condensed matter typically involves a trade-off between structural order and flexibility. As the extent and directionality of interactions between atomic or molecular components increase, materials generally become more ordered but less compliant, and vice versa. Nevertheless, high levels of structural order and flexibility are not necessarily mutually exclusive; there are many biological (such as microtubules, flagella , viruses) and synthetic assemblies (for example, dynamic molecular crystals and frameworks) that can undergo considerable structural transformations without losing their crystalline order and that have remarkable mechanical properties that are useful in diverse applications, such as selective sorption , separation , sensing and mechanoactuation . However, the extent of structural changes and the elasticity of such flexible crystals are constrained by the necessity to maintain a continuous network of bonding interactions between the constituents of the lattice. Consequently, even the most dynamic porous materials tend to be brittle and isolated as microcrystalline powders , whereas flexible organic or inorganic molecular crystals cannot expand without fracturing. Owing to their rigidity, crystalline materials rarely display self-healing behaviour . Here we report that macromolecular ferritin crystals with integrated hydrogel polymers can isotropically expand to 180 per cent of their original dimensions and more than 500 per cent of their original volume while retaining periodic order and faceted Wulff morphologies. Even after the separation of neighbouring ferritin molecules by 50 ångströms upon lattice expansion, specific molecular contacts between them can be reformed upon lattice contraction, resulting in the recovery of atomic-level periodicity and the highest-resolution ferritin structure reported so far. Dynamic bonding interactions between the hydrogel network and the ferritin molecules endow the crystals with the ability to resist fragmentation and self-heal efficiently, whereas the chemical tailorability of the ferritin molecules enables the creation of chemically and mechanically differentiated domains within single crystals.

Scalable Synthesis of Multifunctional Epidermis‐Like Smart Coatings

“…For example, E and H of (PVA‐TA) 1 @(PVA‐TA‐MTM 70% ) 1 are 34.3 ± 1.4 and 1.65 ± 0.09 GPa, respectively (Figure b and Table ). These values can be comparable with our previous work and are much higher than other inorganic reinforcing smart coatings (Figure c) . Importantly, E represents the highest value achieved and H even reaches the levels of tooth enamel ( H : 1.1–4.9 GPa) .…”

“…This evolutionary strategy for alleviating and restoring damage has provided important insights for developing healing mechanism in artificial systems . Many biomimetic designs have been established aiming at mimicking the structural characteristics of natural materials for improving healing performances of artificial counterparts as exemplified by the vascular network, dynamic bonding, mussel, and skin‐inspired self‐healing . Recent studies on “active” healing by gobbling carbon from the air or self‐growing gels by learning from muscle training represent new exciting directions.…”

Structural Insight into Binary Protein Metal–Organic Frameworks with Ferritin Nanocages as Linkers and Nickel Clusters as Nodes

“…utilized pseudo spherical ferritin molecules with eight zinc ions decorated on their outer surface as huge nodes and synthetic ditopic hydroxamic acid as linkers to construct protein MOFs where ferritin molecules arrange into the desired body‐centered cubic (bcc) lattice . By taking advantage of the metal coordination, the Tezcan group also rebuilt single ferritin molecules with cupper and controlled the expansion and contraction of polymer‐bonded ferritin crystals with different metals . Due to the complicated, heterogeneous protein surfaces compared to synthetic small organic molecules, the construction of protein MOFs—especially binary MOFs—to replace small organic molecules as linkers is still a challenge.…”

“…[26,27] By taking advantage of the metalc oordination, the Te zcan group also rebuilts ingle ferritin molecules with cupper and controlled the expansion and contraction of polymer-bonded ferritin crystalsw ith different metals. [28,29] Due to the complicated, heterogeneous protein surfaces compared to synthetic small organic molecules, the construction of protein MOFs-especially binaryM OFs-tor eplace small organic molecules as linkers is still ac hallenge.…”

Thermally Induced Reversible Self‐Assembly of Apoferritin–Block Copolymer Complexes

“…Ferritin cage can also be further modified to enable the design of stimuli‐responsive assemblies. Polymers can impart the systems with properties untypical for highly ordered structures, like self‐healing and thermo‐responsiveness. Covalently modified thermo‐responsive ferritin has been reported, but the modification requires extra synthesis steps and is irreversible.…”