Recently, catechol-containing polymers have been extensively developed as promising materials for surgical tissue adhesives, wound dressing, drug delivery depots, and tissue engineering scaffolds. Catechol conjugation to the polymer backbone provides adhesive properties to the tissue and does not significantly affect the intrinsic properties of the polymers. An example of a catecholic polymer is catechol-conjugated hyaluronic acid. In general, hyaluronic acid shows excellent biocompatibility and biodegradability; thus, it is used in various medical applications. However, hyaluronic acid alone has poor mechanical and tissue adhesion properties. Catechol modification considerably increases the mechanical and underwater adhesive properties of hyaluronic acid, while maintaining its biocompatibility and biodegradability and enabling its use in several biomedical applications. In this review, we briefly describe the synthesis and characteristics of catechol-modified hyaluronic acid, with a specific focus on catechol-involving reactions. Finally, we discuss the basic concepts and therapeutic effects of catechol-conjugated hyaluronic acid for biomedical applications.
Boston ivy (Parthenocissus tricuspidata) climbs brick walls using its tendril disks, which excrete a sticky substance to perform binding and attachment. While the cellular structures and adhesive substances involved have been identified for decades, their practical applicability as an adhesive has not yet been demonstrated. A Boston ivy disk‐inspired adhesive film patch system is reported in which structural and compositional features of the Boston ivy disk are mimicked with a form of thin adhesive film patches. In analogy to the sticky disk of a mature ivy in which porous microchannels are occupied by catechol‐containing microgranules on the bound site, 3,4‐dihydroxylphenylalanine bolaamphiphile nanoparticle (DOPA‐C7 NP)‐coated alginate microgels are two‐dimensionally positioned into the cylindrical holes that are periodically micropatterned on the flexible stencil film. Finally, it is demonstrated that the pressurization of the patch breaks the microgels filled in the holes, releasing the polysaccharides and leading to crosslinking with DOPA‐C7 NPs via ligandation with combined Ca2+ and Fe3+ ions, thus enabling development of a pressure‐mediated adhesion technology.
Inspired by adhesive mussel proteins, nanospherical self-assemblies were prepared from bolaamphiphiles containing 3,4-dihydroxyphenylalanine (DOPA) moieties, and a suspension of the bolaamphiphile assemblies was used for the preparation of a patterned surface that enhanced cell adhesion and viability. The abundant surface-exposed catechol groups on the robust bolaamphiphile self-assemblies were responsible for their outstanding adhesivity to various surfaces and showed purely elastic mechanical behaviour in response to tensile stress. Compared to other polydopamine coatings, the spherical DOPA-bolaamphiphile assemblies were coated uniformly and densely on the surface, yielding a nano-embossed surface. Cell culture tests on the surface modified by DOPA-bolaamphiphiles also showed enhanced cellular adhesivity and increased viability compared to surfaces decorated with other catecholic compounds. Furthermore, the guided growth of a cell line was demonstrated on the patterned surface, which was prepared by inkjet printing using a suspension of the self-assembled particles as an ink. The self-assembly of DOPA-bolaamphiphiles shows that they are a promising adhesive, biocompatible material with the potential to modify various substances.
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