Biocompatible adhesives are becoming a vital ingredient in medical science. Despite numerous reports, developing adhesive materials combining strong adhesion, biocompatibility, and biodegradation remains challenging. A sticky coacervate of water-soluble polymers formed with natural tannins such as tannic acid has attracted recent interest as an appealing alternative by exploiting their inherent biocompatibility and biodegradability. However, being a viscoelastic liquid, the relatively low elastic modulus and weak shear strength limited its use.<br/><br/>Here we present a new adhesive formulation consisting of an amphiphilic, biodegradable, biocompatible block copolymer with tannic acid. Our design strategy bridges self-assembled, temperature-sensitive block copolymer nanostructures with tannic acid as a sticky and biodegradable polyphenolic compound. The formulation further uniquely offers step-by-step increases in adhesion strength via heating-cooling cycles. Combining the modular design with the thermal treating process enhances mechanical properties up to five orders of magnitude compared to the homopolymer formulation. Whereas much higher high cohesion and shear strengths could be achieved, the adhesive retains good tackiness provided by the wet hydrogen-bonded matrix. With this heat-treated adhesive, we demonstrate preliminary results for noninvasive, sustainable, follicle-free hair transplantation. We believe this study opens a new direction in bio-adhesive formulation strategies by utilizing block copolymer nanotechnology for systematic and synergistic control of the material’s properties.

Biodegradable block copolymer-tannic acid adhesive

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