Leaf-inspired bandage heals, hints and vanishes

Chronic wounds are miniature ecosystems where rising pH, excess exudate and bacterial biofilms stall healing and trigger repeated hospital visits. Conventional dressings absorb or medicate, but rarely do both while telling clinicians when trouble starts. The new study takes design cues from foliage: a vein-like scaffold of TEMPO-oxidised cellulose fibres gives tensile strength, while a spongy mesophyll layer of polyvinyl alcohol and cellulose nanofibers stores anthocyanin pigments that change colour with acidity.

Covalent grafting of neomycin to the cellulose skeleton prevents the antibiotic from washing away; instead the aminoglycoside punches holes in approaching bacteria through sustained contact. When liquid enters the pores the rigid aerogel collapses into a soft hydrogel, a phase transition that momentarily lowers local pressure and draws additional fluid—along with planktonic pathogens—from deeper tissue. Measurements in saline or rabbit blood recorded a vacuum of –1.3 mmHg, enough to keep the wound bed moist but not macerated.

Mechanical tests showed the composite withstands 2.5 MPa tensile stress, four times the modulus of untreated cellulose fabric, yet folds like a textile for easy application. Hydrophilicity is extreme: a water droplet disappears in under one second and the material locks away 1 300 % of its own weight in fluid while remaining structurally intact.

Colour performance is equally dramatic. At the near-neutral pH of healthy skin the anthocyanin flavylium cation displays a pale pink; as alkalinity creeps toward pH 9—typical of Pseudomonas or Staphylococcus colonisation—the molecule deprotonates to a purple quinonoid base, giving carers an unmistakable visual alarm without electronics or batteries. Bench-top release curves show 90 % of pigment diffuses within 24 h, scavenging DPPH, ABTS and hydroxyl radicals with >93 % efficiency and suppressing oxidative stress that can delay granulation tissue formation.

In vivo data cement the concept. Mice bearing 7 mm infected excisions were treated with either the experimental dressing, its individual components or a market-leading hydrocolloid. After seven days the dual-network group shaved wound area to 12 % of original size versus 20 % for the commercial control, while histology revealed denser neovascularisation and newly sprouting hair follicles. Gene-expression assays of excised skin showed a 70 % drop in IL-1β and TNF-α transcripts relative to untreated lesions, corroborating the anti-inflammatory effect of released anthocyanin.

Biocompatibility passed key thresholds: NIH3T3 fibroblasts retained 80 % viability after 48 h contact and haemolysis stayed below 3 %, well under the 5 % safety limit. Soil-burial trials found complete disintegration within three months, leaving no microplastic residue—a stark contrast to petrochemical gauze that persisted unchanged.

The authors argue that integrating sensing, drug delivery and exudate management into a single cellulose platform sidesteps the multi-layer laminations that drive up cost and compromise breathability. Because raw materials are commodity wood pulp and food-grade blueberry extract, large-scale roll-to-roll production is “technically trivial and economically realistic,” they contend.

If regulatory pathways are cleared the dressing could reach clinics within three to five years, offering diabetics, burn patients and surgical wards a low-cost pathway to faster, complication-free healing while slashing the 2.5 million tonnes of medical plastic waste generated globally each year.

Article URL:
https://www.sciencedirect.com/science/article/pii/S2369969825001063