Adhesive κ-Carrageenan Hydrogels by Polyphenol Intervention.

Area of Science:

• Materials Science
• Biopolymer Engineering
• Food Science

Background:

• Kappa-carrageenan (κ-CRG) forms thermo-reversible hydrogels but has limited mechanical strength and controlled disintegration due to sulfate repulsion.
• Plant-derived polyphenols offer potential for modifying biopolymers.

Purpose of the Study:

• To investigate how plant-derived polyphenols reprogram κ-CRG hydrogels through sulfate-directed binding.
• To explore the impact of polyphenol structure and binding mechanism on κ-CRG gel properties.

Main Methods:

• Utilized tannic acid (TA) and pyrogallol to interact with κ-CRG hydrogels.
• Assessed gel transparency, storage modulus, and mechanical properties.
• Investigated gel behavior in simulated gastric and intestinal fluids.
• Examined adhesion to various substrates.

Main Results:

• Tannic acid selectively bound to κ-CRG sulfate groups, increasing storage modulus by over 5-fold and forming transparent gels.
• Sulfate-free agarose showed precipitation with TA, confirming sulfate-mediated specificity.
• Monovalent pyrogallol interactions offered partial reinforcement but lacked cooperative stabilization.
• TA/κ-CRG gels exhibited rapid disintegration and strong adhesion, while pyrogallol/κ-CRG gels were more stable.

Conclusions:

• Plant polyphenols, particularly tannic acid, can effectively reprogram κ-CRG hydrogels via sulfate-directed binding.
• This approach offers a food-grade method to tune κ-CRG mechanics, thermal behavior, adhesion, and disintegration.
• The findings enable tailored applications for κ-CRG in food and biomedical fields.