Fabrication of Anisotropic Silk Fibroin-Cellulose Nanocrystals Cryogels with Tunable Mechanical Properties, Rapid Swelling, and Structural Recoverability via a Directional-Freezing Strategy

Abstract

A hierarchically anisotropic structure is widely found in natural materials, such as tendons and wood for performing specific functions. However, fabrication of anisotropic materials with interconnected macropores achieving anisotropic structural and mechanical characteristics simultaneously is still a major challenge. Silk fibroin (SF) has attracted great interest as a multifunctional biomaterial, owing to its remarkable mechanical properties, excellent biodegradability, and biocompatibility. In this work, we present a directional-freezing strategy for preparing anisotropic SF-cellulose nanocrystal (CNC) cryogels based on multiple hydrogen bonds between SF, poly(ethylene glycol) (PEG), and cellulose nanocrystals (CNCs) with an orientated microstructure and freezing-direction-dependent mechanical performance, which are reminiscent of natural tissues. The incorporated CNCs acting as connected bridges in the hierarchically porous network can not only endow the SF-CNC cryogels with improved structural stability but also increase the β-sheet amount to improve the cross-link density of an SF network, which collaboratively improved the mechanical properties with Young's modulus of 709 and 160 kPa along the direction parallel and perpendicular to the freezing direction, respectively. Intriguingly, the SF-CNC cryogels display rapid swelling behavior and structural recoverability ascribed to the macroporous structure and abundant hydrophilic groups. Additionally, the resultant SF-CNC cryogels are degradable in a protease XIV solution and the degradation behavior is ascribed to the surface erosion of the SF-CNC cryogels and breakdown of the β-sheet crystalline structure of silk fibroin. Overall, this study suggests a facile and ecofriendly approach via directional freezing to fabricate anisotropic SF-CNC cryogels, which opens up a new prospect for soft-tissue engineering applications.

Silk Fibroin Cryogel Building Adaptive Organohydrogels with Switching Mechanics and Viscoelasticity

“…Moreover, the increase in the plateau stress of OHGs with increasing x C18A also reflects increasing stability of their pores filled with the organogels (inset of Figure b). We should note that the compressive mechanical properties of OHGs are much higher than those of the cryogels ,,,− and OHGs reported before. − ,− ,,, …”

“…Cryogelation, that is, gelation conducted below the freezing point of the reaction system is a very efficient method for the preparation of tough macroporous materials having an interconnected open porous architecture. − In contrast to the classical hydrogels, the cryogels possess permanent pores independent of the drying conditions, and exhibit extraordinary mechanical properties such as superior compressibility (>95%) and fatigue resistance in addition to rapid water absorption/desorption capability occurred within seconds. ,− These abilities provide them an advantage over the traditional hydrogels, especially for load bearing applications.…”

Patternable Nanocellulose/Ti3C2Tx Flexible Films with Tunable Photoresponsive and Electromagnetic Interference Shielding Performances

“…32 CNCs with nano-sized rodlike structures exhibit superior crystallinity and orientation. 33 BC originated from some anaerobic bacteria and have high purity and high polymerization, which gives them excellent mechanical properties. 34 Overall, the common characteristic is that the coexistence of hydrophilic −OH groups and hydrophobic −CH groups causes the nanocellulose to have excellent dispersion in water, 35,36 facilitating its potential uniform incorporation with MXene.…”

Polyacrylamide‐Conductive Hydrogel Modified with Regenerated Silk Fibroin Resulting in Low‐Temperature Resistance and Self‐Healing Properties for Flexible Electronic Skin

“…Regenerated Silk Fibroin (RSF) hydrogels are easily prepared from silk fibroin solution. It is usually due to the existence of β‐sheet structures [33] . The key factor behind these exciting properties stems comes from the rigid crystalline β‐sheets and highly convoluted amorphous domains.…”

“…It is usually due to the existence of β-sheet structures. [33] The key factor behind these exciting properties stems comes from the rigid crystalline β-sheets and highly convoluted amorphous domains. They are able to dissipate mechanical energy across the fibroin backbone-A rare mixture which is capable of producing high stiffness and toughness in the same system.…”