• Application of tannic acid hydrogels in biomedical engineering
  • Hadis Shahri,1,* Jhamak Nourmohammadi,2
    1. College of Interdisciplinary Science and Technology, University of Tehran
    2. College of Interdisciplinary Science and Technology, University of Tehran


  • Introduction: Polyphenols are a class of naturally occurring organic compounds widely distributed in plants, fruits, and vegetables. They are also present in beverages like coffee and red wine. These compounds exhibit antioxidant properties, meaning they can protect the human body from oxidative damage caused by free radicals. Structurally, polyphenols contain multiple phenolic units, the number and specific characteristics of which underpin their distinctive physical, chemical, and biological properties. Polyphenols can be classified into several categories, including flavonoids, phenolic acids, non-flavonoid polyphenols such as tannins, lignans, and stilbenes. Tannic acid is a polyphenol belonging to the hydrolyzable tannins, and due to its abundance of carbonyl and hydroxyl groups, it exhibits both hydrophilic and hydrophobic properties. This unique structural feature enables it to form hydrogen bonds with various substances, including proteins and synthetic materials. Hydrogels are soft, hydrophilic materials characterized by a three-dimensional cross-linked polymer network. This structure allows them to absorb and retain large volumes of water without dissolving. This unique structural feature enables hydrogels to mimic the physical and mechanical properties of living tissues closely. This structural similarity imparts excellent biocompatibility, making hydrogels highly suitable for a broad spectrum of biomedical applications, including drug delivery, tissue engineering, antibacterial therapy, and related fields.
  • Methods: For this review, the Google Scholar, PubMed, and Scopus databases were used as the primary sources of literature. Articles in this database were restricted to the years 2019 to the present by using an advanced search. Relevant articles were then identified based on specific keywords, categorized accordingly, and subjected to detailed analysis.
  • Results: Tannic acid–based hydrogels have been widely investigated for diverse biomedical applications. In wound healing, tannic acid–based hydrogels facilitate tissue repair by scavenging free radicals, inhibiting bacterial growth, and stimulating fibroblast migration and angiogenesis. The incorporation of tannic acid into polymeric matrices such as polycaprolactone, polyvinyl alcohol, and chitosan has been shown to enhance hydrophilicity, promote collagen deposition, and improve antibacterial performance. Advanced formulations, including dual-layer hydrogels and tannic acid–iron complexes, have also demonstrated self-healing capacity and enhanced mechanical stability, making them promising candidates for wound dressings, particularly in diabetic ulcers and infected wounds. In drug delivery, tannic acid contributes to pH-responsive release and high drug-loading efficiency. Studies report that tannic acid–based carriers can achieve sustained and targeted delivery of therapeutic agents, with improved biocompatibility and reduced cytotoxicity. The ability of tannic acid to form reversible hydrogen bonds and interact with nanomaterials has enabled the development of multifunctional platforms that combine anticancer, antibacterial, and antioxidant effects. In bone tissue engineering, tannic acid hydrogels have been reported to enhance the osteogenic differentiation of stem cells, reduce oxidative stress, and facilitate new bone formation. Through crosslinking with hydroxyapatite and proteins, these hydrogels exhibit improved compressive strength and favorable biological interactions, underscoring their potential in skeletal repair. Overall, current evidence highlights tannic acid hydrogels as versatile biomaterials with significant therapeutic promise in wound healing, drug delivery, and bone regeneration.
  • Conclusion: The development of biocompatible and functional biomaterials remains a major challenge in tissue engineering. Tannic acid has emerged as a promising bioactive compound that can act as a versatile crosslinker for a wide range of macromolecules, including proteins, carbohydrates, and both natural and synthetic polymers. Through diverse physical and chemical interactions, tannic acid contributes to the formation of hydrogels, complexes, and nano-capsules, either by direct or indirect incorporation. Direct incorporation enables the synthesis of injectable hydrogels. However, it may also disrupt the primary crosslinking network because of multiple interactions. In contrast, indirect incorporation provides stronger adhesive and self-healing properties; however, it may restrict the design of injectable systems for clinical emergencies. Importantly, the interactions between tannic acid and polymers are pH-dependent, influencing its protonation and binding capacity. This property enables the controlled release of bioactive agents with anti-inflammatory, antibacterial, and anticancer activities. As a result, tannic acid is positioned as a valuable therapeutic component for wound healing, drug delivery, and tissue engineering. Despite its potential, challenges remain in fully understanding the binding mechanisms of tannic acid–polysaccharide systems, underscoring the need for further research to optimize their biomedical applications.
  • Keywords: Tannic acid, Hydrogels, Wound healing, Drug delivery