"Effective for Therapeutic and Functional Cosmetics": Design Strategy Developed to Enhance Hydrogel Performance

A technology has been developed that enhances the strength of hydrogels while allowing the control of their adhesiveness and degradation rate. Hydrogels are gel materials widely used in the bio and healthcare fields, such as in contact lenses, acne patches, and wound dressings.

On June 9, KAIST announced that the research team led by Professor Lee Ehsin of the Department of Chemistry has developed a new material design strategy for seaweed-derived hydrogels using tannic acid, a type of natural antioxidant polyphenol.

Hydrogels can retain drugs and active ingredients even when in close contact with the skin, making them useful as: ▲ drug delivery systems ▲ wound dressings (medical dressings that help protect and heal wound sites) ▲ scaffolds for tissue engineering (structures that assist artificial tissue regeneration) ▲ cosmetic ingredients, among other applications.

(From left) Han-Yeol Yang, researcher, Hae-Shin Lee, professor. KAIST

The newly developed design strategy focuses on maximizing these roles by improving the mechanical strength and adhesiveness of hydrogels, and by controlling their degradation rate.

The research team focused on 'kappa-carrageenan (κ-carrageenan),' a type of hydrogel material. Kappa-carrageenan is a natural polymer extracted from red algae such as Eucheuma, and is used to enhance viscosity and maintain the form of foods such as jellies and sauces.

However, there have been limitations in improving the performance of hydrogels made from kappa-carrageenan. The sulfate group structure, which is abundant in kappa-carrageenan molecules, creates intermolecular repulsion, similar to how like poles of a magnet repel each other. This repulsion interferes with the formation of a dense structure, making it difficult to enhance the strength and adhesiveness of hydrogels or to control their degradation rate to a desired level.

To solve this problem, the research team focused on tannic acid, a natural polyphenol. Polyphenols are natural substances produced by plants to protect themselves from ultraviolet rays and pests, and they have the property of being able to bind to multiple substances simultaneously.

In particular, tannic acid has multiple binding sites (galloyl groups), which strongly interact with the sulfate groups in kappa-carrageenan, linking the molecules together. The research team determined that this can be used to reinforce the hydrogel structure.

AI generated image. KAIST

When sulfate groups interacted with tannic acid, the hydrogel became even stronger. The storage modulus (an indicator of gel firmness and elasticity) of kappa-carrageenan hydrogel containing tannic acid was 1,632 Pa, which is more than five times higher than that of pure kappa-carrageenan hydrogel (294 Pa).

This means that the hydrogel can maintain its shape stably even under external pressure or deformation. In other words, the durability and usability of wound dressings and drug delivery patches can be improved.

The research team also succeeded in simultaneously achieving rapid degradability and strong adhesiveness in hydrogels. The hydrogel containing tannic acid decomposed relatively quickly in experiments simulating the human stomach and intestinal environment, and showed strong adhesion to both skin and rough surfaces.

Professor Lee Ehsin stated, "This study is significant in that it presents a design principle for simultaneously controlling the strength, adhesiveness, and degradation rate of hydrogels using only natural ingredients, without chemical synthesis," adding, "The research team expects that these findings will be expanded and applied as a safer and simpler natural polymer gel platform in the food, cosmetics, and biomaterial fields in the future."

This content was produced with the assistance of AI translation services.