Iron(iii)-cross-linked alginate hydrogels: a critical review

Abstract

Ionotropic alginate hydrogels are versatile materials for a wide range of applications. Their biocompatibility and biodegradability have made them perfect candidates for biomedical applications such as tissue engineering and drug...

A review of recent advances in metal ion hydrogels: mechanism, properties and their biological applications

“…[75][76][77] The introduction of metal ions further optimized the performance of the hydrogel. 66,78,79 The redox reaction was one of the most common response systems brought about by metal coordination. 80 Metal ions formed different chemical bonds based on the change of valence state of redox reactions, which changed the original properties of physical and chemical states, and then formed different hydrogel networks (Fig.…”

Polyelectrolyte Hydrogels for Tissue Engineering and Regenerative Medicine

“…Alginate can from gels when complexed with divalent and trivalent cations such as Ca 2+ , Ba 2+ or Fe 3+ [51] . For the divalent cations, the gelation is understood to proceed via an “egg‐box” model involving the carboxylate and hydroxyl groups on the alginate chains, although the mechanism for trivalent ions remain unclear [51a] . Besides alginate, other carbohydrates that form gels with metal cations have been identified (Figure 6b).…”

Recent Trends in Sense‐and‐Release Platforms Employing Electrochemically‐Triggered Payload (Drugs) Release – A Review

“…Innately the acid form of alginate is not water‐soluble, however its salt‐form (Na + /K + ) can be dissolved and instantaneously crosslinks to form hydrogels when certain divalent (Ca 2+ , Ba 2+ , Pb 2+ ) or trivalent (Fe 3+ , Al 3+ ) cations penetrate and arrange within the interconnected polymer network [30–34] . Such Ionotropic alginate hydrogels have been employed for decades due to their versatility as materials and the wide range of potential applications [29,35,36] . In particular, their biocompatibility and biodegradability have allowed for in vivo biomedical applications, environmental science, food science, and the textile industry, among others.…”

“…In particular, their biocompatibility and biodegradability have allowed for in vivo biomedical applications, environmental science, food science, and the textile industry, among others. Recently, increased publication activity surrounding ionotropic alginate hydrogels have occurred [29,37,38] . This uptick in research interest in alginate hydrogels is most likely explainable due to Fe 3+ cation use as hydrogel crosslink, due to both Fe 3+ ’s chemistry interest as well as the novel features imparted to alginate hydrogels by trivalent Fe 3+ crosslinking, compared to the opposite effect of in its divalent form (Fe 2+ ).…”

“…Although alginate salts can undergo sol‐gel hydrogel formation in the presence of both divalent and trivalent cations, when considering iron, only the Fe 3+ is truly effective at hydrogel structure maintenance. This is explained by the “hard” nature of Fe 3+ in comparison to the “soft” Fe 2+ , the two of which coordinate with negative and neutral ligands, respectively [29] . Thus, considering alginate's carboxylate structure the increased effectivity of Fe 3+ coordination in aqueous solutions becomes evident.…”