A joint research team from Korea Advanced Institute of Science and Technology (KAIST) said on Wednesday they developed a bio-friendly adhesive by mixing tannic acid with bio-compatible polymers to improve existing hair transplant methods.

The KAIST team of researchers developed a bio-friendly adhesive which improves upon existing hair transplantation methods.
The KAIST team of researchers developed a bio-friendly adhesive which improves upon existing hair transplantation methods.

Tannic acid is a type of polyphenol found in fruit shells, nuts, and cacao. Due to its strong adhesion and coating power, it quickly binds to other substances. When water is mixed with dissolved polymer and tannic acid, coacervate, small sticky liquid drops may sink. However, together with biocompatible polymers, it can be used as a low-toxicity medical adhesive.

Still, coacervate is fundamentally close to liquid and cannot withstand large forces, so there is a limit to improving the adhesion properties.

To resolve this issue, the researchers managed to increase adhesion by designing a structure combining polyethylene glycol (PEG) and polylactic acid (PLA), substances licensed for human use by the U.S. Food and Drug Administration (FDA). While PEG, which is widely used in eye drops and creams, dissolves well in water, PLA, which is well known as bioplastic derived from lactic acid, does not dissolve in water.

Coacervate, which is made by mixing micelle and tannic acid, behaves like a solid due to the solid PLA component. Thus, it exhibits an improved elastic modulus by more than a thousand times compared to PEG to withstand much stronger forces when adhered.

Through repeated heat-cooling cycles, the researchers improved the physical properties by more than a hundred times, due to the interaction between the aligned micelles and tannic acid gradually becoming solid.

Moreover, animal experiments confirmed the bio-adhesive’s application for hair transplantation by applying it to the ends of hair using the properties of materials that are less irritating to the skin and easy to decompose.

Professor Lee Hae-shin of KAIST said that he hopes this new follicle-free hair transplantation method of transferring hair follicles can overcome the existing transplant limitations as the surgery does not require invasive tissue resections or follicle extraction procedures and can be repeated if hair loss results.

The results of the study were published online in the international journal, JACS Au, with the title, “Biodegradable Block Copolymer–Tanic Acid Glue.”

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