Tannic acid–metal biomaterials for skin repair: Principles, immune microenvironment modulation, and translational perspectives

Abstract Chronic skin wounds remain difficult to treat because infection, oxidative stress, vascular insufficiency, matrix dysfunction, and persistent inflammation reinforce one another and trap repair in a nonhealing state. Tannic acid and bioactive metal ions are increasingly combined to address this problem, yet the literature is often fragmented between TA‐centered formulations, free‐ion strategies, and multifunctional TA–metal assemblies. This review examines these three therapeutic logics in parallel and asks not only what each platform can do but also what wound bottleneck it is actually designed to solve. The discussion first clarifies what TA alone has contributed before TA–metal systems emerged, then evaluates the biological power and formulation risk of free metal ions, and finally analyzes how coordination chemistry enables retention, controlled ion presentation, redox balance, adhesion, and microenvironmental modulation in TA–metal biomaterials. Representative studies are re‐read through wound problems, material format, evidence depth, and translational meaning rather than as a simple catalog of positive outcomes. Particular attention is given to immune microenvironment remodeling, macrophage‐centered claims, stage‐adaptive design, and the distinction between established evidence and attractive but still inferential mechanistic narratives. By integrating material design logic with biological interpretation and translational criteria, this review provides a practical framework for selecting, evaluating, and advancing TA–metal biomaterials for skin repair.