Recent Developments in Tough Hydrogels for Biomedical Applications

Abstract

A hydrogel is a three-dimensional polymer network with high water content and has been attractive for many biomedical applications due to its excellent biocompatibility. However, classic hydrogels are mechanically weak and unsuitable for most physiological load-bearing situations. Thus, the development of tough hydrogels used in the biomedical field becomes critical. This work reviews various strategies to fabricate tough hydrogels with the introduction of non-covalent bonds and the construction of stretchable polymer networks and interpenetrated networks, such as the so-called double-network hydrogel. Additionally, the design of tough hydrogels for tissue adhesive, tissue engineering, and soft actuators is reviewed.

Crystallinity, reversibility, and injectability of physically crosslinked poly(vinyl alcohol) and poly(ethylene glycol) hydrogels

“…Physically crosslinked PVA/PEG hydrogels are widely used for biomedical applications due to their biocompatibility and easily altered mechanical properties, enabling their use in more biostable and load‐bearing applications . Specifically, studies have shown that the mechanical properties of these hydrogels can be enhanced by inducing different degrees of crystallinity .…”

“…Physically crosslinked PVA/PEG hydrogels are widely used for biomedical applications due to their biocompatibility and easily altered mechanical properties, enabling their use in more biostable and load-bearing applications. [1][2][3][4][5][6][7] Specifically, studies have shown that the mechanical properties of these hydrogels can be enhanced by inducing different degrees of crystallinity. 3,8,9 For instance, the formation of crystallite structures in a hydrogel network can be induced via processes such as freeze-thaw cycles or radiation sterilization methods, or naturally occur via aging under benign storage conditions.…”

“…[1][2][3] While hydrogels are typically mechanically weak, the mechanical properties of these biomaterials can be greatly improved through different noncovalent (physical) or covalent (chemical) crosslinking. 1 Physically crosslinked hydrogels can include a variety of electrostatic interactions between polymer chains (i.e., hydrogen bonding, hydrophobic interactions) and the formation of crystalline regions in the hydrogel network. 2 Physically crosslinked hydrogels offer higher degrees of biocompatibility, as no chemical residues reside in the network, 2 making these types of hydrogels attractive for clinical use.…”

Microbial Exopolysaccharides as Drug Carriers

“…Gels can be obtained by using crosslinkers or by providing the experimental conditions for the production of physical chain entanglements. Lastly, hydrogels can also mimic the extracellular matrix and be used as a platform for drug release or for cell attachment and proliferation [ 34 , 35 , 36 ].…”

Tough Polyelectrolyte Hydrogels with Antimicrobial Property via Incorporation of Natural Multivalent Phytic Acid

“…However, due to the nature of covalent bonds, damages caused by continuous stress results in permanent damage to IPN, leading to the loss of the mechanical properties over time [7]. To address the problem, many efforts have been made to incorporate or alter covalent crosslink with reversible physical crosslinker for fabricating tough hydrogels [1]. The physical crosslinkers can be temporally disrupt and recover when stress is removed, hence providing force dissipation within the hydrated network.…”