Tea compound boosts seaweed hydrogel strength fivefold, while tuning adhesion and breakdown

Tea compound boosts seaweed hydrogel strength fivefold, while tuning adhesion and breakdown Sadie Harley Scientific Editor Robert Egan Associate Editor Could wound healing dressings adhere better, and could drug delivery patches become more sophisticated? A KAIST research team has developed a technology that leverages natural ingredients derived from plants to increase the strength of a seaweed-based hydrogel (a gel material that contains a large amount of water while maintaining its shape) by more than fivefold, while also controlling its adhesiveness and degradation rate. The research team, led by Professor Haeshin Lee of the Department of Chemistry, developed a new material design strategy that uses tannic acid—a type of polyphenol, which is a natural antioxidant abundant in tea and fruits—to enhance the mechanical strength and adhesiveness of seaweed-derived hydrogel and control its degradation rate. The work is published in the journal Biomimetics. Hydrogel is a high-moisture gel material used in contact lenses, acne patches, mask packs and wound healing dressings. Because it can adhere closely to the skin while holding drugs or active ingredients, it is used in various bio- and health care-related fields, such as drug delivery systems (materials that effectively deliver drugs to desired sites), wound dressings (medical dressings that protect wounds and aid healing), tissue engineering scaffolds (structures that help regenerate artificial tissue) and cosmetic materials. Why carrageenan needed help Among various hydrogel materials, the research team focused on κ-Carrageenan. κ-Carrageenan is a natural polymer extracted from red seaweed (rhodophytes) such as agar-agar, and it is a familiar food ingredient used to increase viscosity and maintain the shape of jellies and sauces. However, there were limitations to improving the performance of hydrogels made with κ-Carrageenan. The κ-Carrageenan molecule contains many structures called sulfate groups, which create intermolecular repulsion—much like magnets with the same pole pushing each other away—and prevent the formation of a dense structure. For this reason, it was difficult to increase the strength and adhesiveness of the hydrogel or adjust the degradation rate to a desired level. To solve this problem, the research team focused on finding a natural substance that could effectively interact with the sulfate groups. As a result, it determined that tannic acid, a natural polyphenol abundant in tea and fruits, could be a promising candidate. Polyphenols are natural ingredients produced by plants to protect themselves from external conditions such as ultraviolet rays or pests, and they have the characteristic of being able to bind with multiple substances simultaneously. In particular, tannic acid has multiple binding sites (galloyl groups), so it was expected to interact strongly with the sulfate groups of κ-Carrageenan and connect the molecules together. The research team believed this characteristic could be used to reinforce the hydrogel structure. How tannic acid strengthened it As a result of the study, it was confirmed that the sulfate group, which was previously considered a factor hindering hydrogel formation, actually acts as a core binding site with tannic acid. In other words, the structure previously considered a weakness played a role in making the hydrogel even firmer when combined with tannic acid. In fact, the storage modulus (an index representing the firmness and elasticity of a gel) of the κ-Carrageenan hydrogel with added tannic acid was approximately 1,632 Pa, showing an improvement of more than fivefold compared with the pure κ-Carrageenan hydrogel (approximately 294 Pa). This means the hydrogel can maintain its shape more stably even under external pressure or deformation, demonstrating that it can increase the durability and usability of wound healing dressings or drug delivery patches. In addition, the research team confirmed that tannic acid stably reinforces the internal network structure (gel network) of the already formed hydrogel, regardless of when the tannic acid is added. This implies that tannic acid connects molecules at multiple points, allowing the internal structure of the hydrogel to remain consistently firm. Balancing adhesion and breakdown Notably, the research team succeeded in achieving rapid degradability and strong adhesiveness simultaneously. In experiments simulating the human stomach and intestinal environments, the hydrogel containing tannic acid degraded relatively quickly while adhering strongly to the skin and rough surfaces. This means wound healing dressings will not easily fall off during use but can naturally degrade after completing their role, and drug delivery patches can be used to stably deliver drugs for a desired period. This study presents a design principle capable of simultaneously controlling the strength, adhesiveness and degradation rate of hydrogel using only food-grade natural ingredients without complex chemical synthesis processes. The research team expects this technology to be used in various bio- and health care-related fields, such as capsules and coating materials for food and functional foods, skin-adhering cosmetics and skin care products, wound dressings, drug delivery patches and tissue engineering scaffolds. Professor Haeshin Lee said, "This study is an example showing that the mechanical strength, adhesiveness, and degradation behavior of hydrogel can be designed together using only naturally derived materials," adding, "It can be expanded into a safer and simpler natural polymer gel platform in the fields of food, cosmetics, and biomaterials." Publication details Han-Yeol Yang et al, Adhesive κ-Carrageenan Hydrogels by Polyphenol Intervention, Biomimetics (2026). DOI: 10.3390/biomimetics11040290 Journal information: Biomimetics