Halochromic composite materials for self-indicating wound-healing textiles: a review

Wound healing is a dynamic and multifactorial process that requires timely assessment to identify changes in the wound microenvironment and to support appropriate clinical management. Conventional wound dressings primarily provide physical protection but generally lack the ability to provide continuous visual information about changing wound conditions. Halochromic composite materials have been investigated as smart wound-healing textiles because they can generate visible, pH-responsive colour changes associated with changes in the wound microenvironment. This review summarizes wound-healing phases, wound types, and factors that influence wound pH, and discusses the chemistry, classification, and pH-responsive behaviour of major halochromic dye systems, including phthalein, azo, fluoran, styryl, and leucotriarylmethane dyes. Recent strategies for integrating pH-responsive dyes into textile-based wound dressings, including conventional dyeing, coating, sol-gel processing, encapsulation, and electrospinning, are also reviewed. Importantly, a colour change in a halochromic material is an indirect indicator of the wound microenvironment and may provide information relevant to infection-associated alkalinization; it should not be interpreted as a direct measurement of wound healing. The review further considers biocompatibility, dye migration, sterilization, and other translational issues that must be addressed before clinical application.