Paradigm Shift for Preparing Versatile M²⁺-Free Gels from Unmodified Sodium Alginate

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Traditional alginate hydrogels rely on divalent metal cations (e.g., CaCl2) for cross-linking.
• This reliance limits applications where metal ion presence is undesirable.

Purpose of the Study:

• To develop novel calcium-free alginate hydrogels using small organic molecules as cross-linkers.
• To investigate the properties and potential applications of these new hydrogel systems.

Main Methods:

• Rapid gelation of sodium alginate solutions at room temperature using poly(carboxylic acid) compounds (e.g., oxalic acid) or dimethyl sulfoxide (DMSO).
• Characterization of thermal, mechanical, and rheological properties of the resulting hydrogels.
• Evaluation of alginate-oxalic acid films for anticancer drug delivery.
• Computational modeling (quantum mechanics and classical force fields) to elucidate gelation mechanisms.

Main Results:

• Successfully prepared Ca2+-free alginate hydrogels using oxalic acid and DMSO.
• Gels exhibited good thermal stability (90-100 °C) and mechanical properties.
• DMSO-based gels showed tunable self-supporting and thixotropic behavior.
• Oxalic acid-based gels demonstrated superior elasticity compared to other formulations.
• Alginate-oxalic acid films showed promise for synergistic anticancer drug delivery.
• Computational studies revealed hydrogen bonding (DMSO) and ionic associations (oxalic acid) as key stabilization mechanisms.

Conclusions:

• Small organic molecules offer a viable alternative to metal salts for alginate hydrogel cross-linking.
• These novel hydrogels possess tunable properties suitable for various applications.
• Alginate-oxalic acid films present a promising platform for advanced drug delivery systems.