Light-Initiated Tissue Adhesives: Photoinitiation Mechanisms, Material Design Strategies, and Tissue Repair Applications.

Conventional mechanical closure remains widely used in tissue repair, but sutures and staples inevitably cause penetration injury and local stress concentration, limiting their effectiveness in fragile tissues and minimally invasive procedures. Tissue adhesives offer atraumatic sealing, yet conventional adhesive formats and curing modes, including thermal initiation, pH-triggered gelation, and preformed patches, often struggle to combine precise control with physiological compatibility. Photoinitiated adhesives enable on-demand initiation of the curing process via external light-triggered in situ polymerization after tissue apposition and positional adjustment, affording active control over crosslinking density and network architecture, while offering the prominent advantages of mild curing conditions, high spatiotemporal precision, and the absence of deleterious byproducts. This review systematically examines the photochemical mechanisms and application suitability of photoinitiating systems, covering the design principles of Type I cleavage, Type II hydrogen abstraction/electron transfer, and cationic photogenerated acid, as well as visible light-sensitized and near-infrared-assisted activation strategies. From a materials engineering perspective, this review further consolidates the construction strategies, adhesion-enhancing mechanisms, and applications of polyethylene glycol-based synthetic systems, photofunctionalized natural polymer systems, mussel-inspired interfacial systems, and multi-network structural systems. This review aims to provide a systematic reference for the rational design, application scenario expansion, and clinical translation of photoinitiated tissue adhesives.