Recent Advances in Polysaccharide‐Based Physical Hydrogels and Their Potential Applications for Biomedical and Wastewater Treatment

Abstract

Polysaccharides are widely employed to fabricate hydrogels owing to their intrinsic properties including biocompatibility, biodegradability, sustainability, and easy modification. However, a considerable amount of polysaccharide‐based hydrogels are prepared by chemical crosslinking method using organic solvents or toxic crosslinkers. The presence of reaction by‐products and residual toxic substances in the obtained materials causes a potential secondary pollution risk and thus severely limits their practical applications. In contrast, polysaccharide‐based physical hydrogels are preferred over chemically derived hydrogels and can be used to address existing drawbacks of chemical hydrogels. The polysaccharide chains of such hydrogel are typically crosslinked by dynamic noncovalent bonds, and the co‐existence of multiple physical interactions stabilizes the hydrogel network. This review focuses on providing a detailed outlook for the design strategies and formation mechanisms of polysaccharide‐based physical hydrogels as well as their specific applications in tissue engineering, drug delivery, wound healing, and wastewater treatment. The main preparation principles, future challenges, and potential improvements are also outlined. It is hoped that this review can provide valuable information for the rational fabrication of polysaccharide‐based physical hydrogel. The specific research works listed in the review can provide a systematic and solid research basis for the reliable development of polysaccharide‐based physical hydrogel.

Stimuli-Responsive Polysaccharide-Based Smart Hydrogels and Their Emerging Applications

“…As ice crystals eject amorphous parts and bulk water crystallization decreases the space for polysaccharide chains, these chains accumulate and align in semifrozen or unfrozen microphase regions. The noncovalent interactions between −COOH, −OH, and −NH 2 functional groups in polysaccharide molecules thus allow them to associate in the liquid microphase. , Moreover, thawing results in the ice crystals melting and instinctively releasing from the hydrogel network, which creates a porous structure. The inter- and intramolecular hydrogen bonds within polymeric network junction zones stabilize the gel structure.…”

“…Another study synthesized chitin/PVA matrix after three freeze–thaw cycles at −20 °C (8 h) and physiological temperature (2 h) . In addition to physicochemical characteristics, such as molecular weight, soluble additives, rheological properties, and the cryotropic treatment regimen within the hydrogel can affect its morphology …”

“…Several polysaccharides such as gellan, carrageenan, agarose, and salecan, to name a few, are subjected to heating for homogenization which, on cooling to room temperature, induces gelation. Phase separation drives the aggregation of polysaccharide chains, resulting in a crystallization region through physical interaction leading to intra- or intermolecular entanglements . In fact, polysaccharides that undergo heating–cooling processes are highly crystalline.…”

“…In industrial wastewater from different sources, toxic heavy metal ions and organic dyes are often present, posing a significant threat to the environment and human health. Since adsorption is a low-cost, easy-to-use, and highly effective wastewater treatment method, it is the most widely used . Moreover, polysaccharide-based hydrogels are ideal adsorbent materials due to their natural origin, porous microstructure, and ease of modification.…”

Polysaccharide-Based Composite Hydrogels as Sustainable Materials for Removal of Pollutants from Wastewater

“…The interest in polysaccharide-based PEC hydrogels has risen lately as a “green” alternative to chemical cross-linked frameworks because of their eco-friendly production without employing toxic reagents and/or solvents [ 64 ]. PEC preparation, as nanoparticles, can be tailored by the chemical structure, charge density and concentration of polyelectrolytes, the type and concentration of coexisting small molecular salts, and pH or temperature, as previously demonstrated [ 65 , 66 , 67 , 68 , 69 ].…”