On-Demand Changeable Theranostic Hydrogels and Visual Imaging-Guided Antibacterial Photodynamic Therapy to Promote Wound Healing

Antibacterial wound dressings are confronted with the challenges in real-time imaging of infected wounds and effective removal of bacterial debris after sterilization to promote the healing process. Herein, injectable theranostic hydrogels were constructed from antimicrobial peptide ε-polylysine (ePL) and polydopamine (PDA) nanoparticles for real-time diagnosis of infected wounds, imaging-guided antibacterial photodynamic therapy (PDT), and on-demand removal of bacterial debris. Ureido-pyrimidinone was conjugated on ePL to produce PLU hydrogels through quadruple hydrogen bonding, and the inoculation of tetrakis(4-carboxyphenyl)porphyrin (TCPP)-loaded PDA (PTc) nanoparticles introduced Schiff base linkages in PLU@PTc hydrogels. The double-cross-linked networks enhance mechanical performance, adhesion strength, and self-healing properties of hydrogels, and the dynamic cross-linking enables their photothermal removal. The injection of PLU precursors and PTc NPs generates in situ sol–gel transformation, and the acid-triggered release of TCPP restores fluorescence emissions for real-time imaging of infected wounds under 410 nm illumination. Then, the released TCPP in the infected wounds is illuminated at 660 nm to launch a precise antibacterial PDT, which is strengthened by the bacterial capture on hydrogels. Hydrogels with wrapped bacterial debris are removed under illumination at 808 nm, and the hydrogel dressing change accelerates healing of infected wounds through simultaneous relief of oxidative stress, regulation of inflammatory factors, acceleration of collagen deposition, and promotion of angiogenesis. Thus, this study demonstrates a feasible strategy for wound infection theranostics through bacterial infection-triggered visual imaging, efficient nonantibiotic sterilization, and on-demand dressing change and bacterial debris removal.