Top-down curing to construct self-retaining and moisture-pumping double-layered dressing with enhanced antibacterial,...

Continuous microenvironment modulation is an ongoing challenge in wound dressing, which includes excessive exudate absorption, oxygen delivery, bacterial inhibition and angiogenesis. Herein, we developed an in situ construction strategy to fabricate a self-retaining double-layered wound dressing, where the top layer precursor was composed of Ca²⁺-containing polyvinyl butyral (PVB) solution dispersed with hydroxypropyl methylcellulose (HPMC) particles, and the bottom one consisted of sodium alginate (Alg) solution blended with Ag-doped mesoporous bioactive glass powders (Ag-MBG). When in use, both precursors were simultaneously squeezed out from the twin nozzles connected to the individual chambers of a twin-chambered syringe, whereby Ca²⁺ in the top layer rapidly migrated downwards to crosslink Alg in the bottom layer, leading to the formation of an Alg/Ag-MBG (AA) functional hydrogel for filling an irregular wound. Meanwhile, with the rapid evaporation of low-boiling solvents, the top layer changed into a PVB/HPMC (PH) membrane covering the AA hydrogel and adhering to the surrounding healthy skin to fix the dressing. Practically, HPMC particles in the top layer acting as "micropumps" could drain the wound exudate out, while Ag-MBG in the bottom layer endowed the dressing with anti-bacterial, hemostatic, and pro-healing functions. The integrally constructed PH-AA dressing achieved over 99% bacterial elimination against both E. coli and S. aureus. Biological assessments indicated that the double-layered dressing possessed excellent biocompatibility and enhanced wound healing, demonstrating a wound closure rate of >97% at day 15. This study provides a facile method to directly construct multi-layer dressings on wounds to meet various wound care requirements.