Self-Healing Hydrogels: Preparation, Mechanism and Advancement in Biomedical Applications

Abstract

Polymeric hydrogels are widely explored materials for biomedical applications. However, they have inherent limitations like poor resistance to stimuli and low mechanical strength. This drawback of hydrogels gave rise to ‘‘smart self-healing hydrogels’’ which autonomously repair themselves when ruptured or traumatized. It is superior in terms of durability and stability due to its capacity to reform its shape, injectability, and stretchability thereby regaining back the original mechanical property. This review focuses on various self-healing mechanisms (covalent and non-covalent interactions) of these hydrogels, methods used to evaluate their self-healing properties, and their applications in wound healing, drug delivery, cell encapsulation, and tissue engineering systems. Furthermore, composite materials are used to enhance the hydrogel’s mechanical properties. Hence, findings of research with various composite materials are briefly discussed in order to emphasize the healing capacity of such hydrogels. Additionally, various methods to evaluate the self-healing properties of hydrogels and their recent advancements towards 3D bioprinting are also reviewed. The review is concluded by proposing several pertinent challenges encountered at present as well as some prominent future perspectives.

Photodynamic Lignin Hydrogels: A Versatile Self-Healing Platform for Sustained Release of Photosensitizer Nanoconjugates

“…Hydrogels are hydrophilic polymeric materials that can hold a large volume of water in their three-dimensional networks . Lately, research has been carried out for various biomedical applications of hydrogels including tissue engineering as well as drug delivery. − Importantly, the hydrogels used as drug delivery systems have shown diverse advantages in antimicrobial photodynamic therapy . Hydrogel-based drug delivery systems are highly advantageous for PDT in comparison to other conventional drug carriers.…”

“…To determine the antimicrobial photodynamic activity of the developed lignin-based nanocomposite as well as bare hydrogels, the live–dead cells staining assay was performed. , For this purpose, propidium iodide (PI) and 4′,6-diamidino-2-phenylindole (DAPI) dyes were used. The suspensions of both untreated and treated microbial cells were placed in the microcentrifuge tubes, followed by the addition of 10 μL of DAPI (0.05 mg/mL) and then propidium iodide (PI, 10 μL, 1 mg/mL).…”

Inosine‐Based Supramolecular Hydrogel for Highly Efficient PD‐L1 Blockade Therapy via Mediating CD8+ T Cells

“…[ 27 ] A variety of dynamic covalent bonds have been introduced into the design of supramolecular hydrogels, including imine bonds, borate ester bonds, Diels–Alder reactions, arylhydrazone bonds, oxime bonds, and disulfide bonds. [ 28 ] The formation of dynamic borate esters in the IPBisoG hydrogel suggests its potential to be employed as an injectable hydrogel for local therapeutic purposes. To explore its injectability, essentially, the viscoelastic property of the IPBisoG hydrogel, rheological measurements were performed.…”

Self-Healing Hydrogels: Development, Biomedical Applications, and Challenges

“…Efforts have been made to design synthetic hydrogels to provide the desired and unique combination of high mechanical properties with strong self-healing behavior by introducing special types of functional groups to provide various reversible chemical networks of hydrogels, such as hydrogen bonds, ionic bonds, hydrophobic interactions, host–guest interactions, π–π stacking, sometimes special covalent bonds, etc. [ 17 ] The most effective strategy for developing tough hydrogels has been observed in polyampholyte hydrogels by introducing a supramolecular system [ 18 ].…”

“…Many review articles already reported various bonding mechanisms for self-healing performance [ 10 , 12 , 17 , 29 , 30 ]. However, the trade-off relation between self-healing and mechanical properties is yet to be reported and scrutinized.…”