A Review of the Mechanism, Properties, and Applications of Hydrogels Prepared by Enzymatic Cross-linking

Hydrogels, as biological materials, are widely used in food, tissue engineering, and biomedical applications. Nevertheless, many issues remain in the preparation of hydrogels by physical and chemical methods, such as low bioaffinity, weak mechanical properties, and unstable structures, which also limit their applications in other fields. However, the enzymatic cross-linking method has the advantages of high catalytic efficiency, mild reaction conditions, and the presence of nontoxic substances. In this review, we evaluated the chemical, physical, and biological methods of preparing hydrogels and introduced three common cross-linking enzymes and their principles for preparing hydrogels. This review introduced the applications and properties of hydrogels prepared by the enzymatic method and also provided some suggestions regarding the current situation and future development of hydrogels prepared by enzymatic cross-linking.

Polyaspartic Acid-Derived Micro-/Mesoporous Carbon for Ultrahigh H2 and CH4 Adsorption

A poly(amino acid)-based approach for scalable synthesis of micro-/mesoporous carbon (PC) with high specific surface area and narrow distribution of micro- and mesopores is presented. Using cross-linked poly aspartic acid as a precursor, PC was obtained by in situ one-step carbonization without the activating agent. The resulting PC had an ultrahigh adsorption capacity for H₂ (4.43 wt %) and CH₄ (4.49 mmol g^-1). This novel method could significantly decrease the wastewater hazards caused by washout of the considerable amount of the activating agent. The PC showed promising application in gas adsorption and storage.

Preparation of poly(aspartic acid) superabsorbent hydrogels by solvent-free processes

Poly(aspartic acid) (PASP) hydrogel is a biodegradable and biocompatible polymer with high water absorbing ability. Traditionally, the production of PASP hydrogel consumes large amounts of organic solvents, i.e., dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). This traditional approach is now considered costly, complex and environmentally unfriendly due to required used solvent disposal. The present research explores two novel methods in preparing PASP hydrogel without organic solvent, by using hydrazine hydrate and ethylene glycol diglycidyl ether (EGDGE) or poly(ethylene glycol) diglycidyl ether (PEGDGE) as the cross-linkers. Absorbent ability and other characteristics are determined. Preparing PASP hydrogel in aqueous solution is promising and finds its use in many applications.

Synthesis of amphiphilic polyaspartamide derivatives and construction of reverse micelles

Large compound reverse micelles consisting of numerous small reverse micelles with polar cores and hydrophobic shells were constructed from amphiphilic polyaspartamide in octanol solution.