Hair-thinning disorders such as alopecia have become major concerns in the modern day regardless of gender, age, or ethnicity. Whereas currently available hair transplant methods are expensive and have common side effects such as scalp laxity and infection during surgery, a newly developed biocompatible glue has been shown to be less irritating to the skin, easily degradable, and cost-efficient. A research team led by Professor Haeshin Lee and Professor Myungeun Seo from the Department of Chemistry developed this new bioadhesive by synthesizing tannic acid (TA) and biocompatible macromolecules for follicle-free hair transplantation. The study, in which Dr. Jongmin Park and Dr. Eunsook Park participated as co-first authors, was published in JACS Au on August 22 under the title “Biodegradable Block Copolymer-Tannic Acid Glue”.

Tannic acid is a type of polyphenol commonly found in fruit shells and nuts. Because of its strong adhesive and coating properties, it quickly binds to other substances and thus can be employed as a key material in glue. When mixed with water and biocompatible polymers, it turns into a coacervate, which is a dense and jelly-like droplet. While they can be used as a less toxic medical adhesive, they are not durable enough for industrial usage.

To solve this problem, the research team found a way to increase its adhesive property by combining two new types of biocompatible polymers: polyethylene glycol (PEG) and polylactic acid (PLA), substances approved by the US Food and Drug Administration (FDA). When the new synthetic product is put into water, PLA clumps together to form micelles while PEG surrounds the micelle surface. The coacervates produced by mixing TA and these micelles exhibit physical properties similar to solids due to the solid PLA component, and show a thousand times greater elasticity compared to PEG. Such characteristics allowed the newly developed bioadhesive to withstand much stronger forces. Additionally, the team repeated a heat-cooling cycle to improve the interaction between the aligned micelles and TA. It was found that the viscoelastic property of TA increased by more than a hundred times as a result. 

The research team showed the possibility of applying the block copolymer-tannic acid glue as an adhesive for hair transplantation through animal experiments. Its excellent performance on biodegradability and safety lived up to the team’s expectations. Professor Lee looks forward to improving existing hair transplant methods — omitting follicle extraction procedures and making the surgery repeatable with the new bioadhesive.