PTT/ PDT-induced microbial apoptosis and wound healing depend on immune activation and macrophage phenotype transformation

Antibiotics show unsuccessful application in biofilm destruction, which induce chronic infections and emergence of antibiotic resistant bacteria. Photodynamic therapy (PDT) and photothermal therapy (PTT), as widely accepted antimicrobial tools of phototherapy, could effectively activate the immune system and promote the proliferation of wound tissue, thus becoming the most promising therapeutic strat-egy to replace antibiotics and avoid drug-resistant strains. However, there is no consensus on whether antibacterial and wound healing achieved by PDT/PTT depend not only on the cytotoxic effect of the treatment itself, but also on the activation of host immune system. In this study, CaSiO3-ClO2 @PDA-ICG nanoparticles (CCPI NPs) were designed as PDT/PTT antimicrobial model material. With the comparison of healing effect between wide-type mice and severely immunodeficient (C-NKG) mice, the dependence of PDT/PTT-induced microbial apoptosis and wound healing on immune activation and macrophage phe-notype transformation was explored and verified. Furthermore, the induced phenotypic transformation of macrophages during PDT/PTT treatment was demonstrated to play crucial role in the improvement of epithelial-mesenchymal transformation (EMT). In summary, this study represents great significance for further identifying the role of immune system activation in antibacterial phototherapy and developing new treatment strategies for biofilm-infected wound healing.Statement of significance A PDT/PTT combination therapy model nanoparticle was established for biofilm-infected wounds. Both microbial apoptosis and wound healing achieved by PDT/PTT combination therapy were highly dependent on the activated immune system, especially the M2 macrophage phenotype. PDT/PTT could promote the polarization of monocytes to the phenotype of M2 macrophages, which promotes EMT behavior of the tissue at the edge of the wound through the secretion of TGF-& beta;1, thus accelerating wound healing.& COPY; 2023 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Antibiotics have shown limited effectiveness in destroying biofilms and lead to the emergence of antibiotic-resistant bacteria and chronic infections. Photodynamic therapy (PDT) and photothermal therapy (PTT) have emerged as potential alternatives to antibiotics by effectively activating the immune system and promoting wound tissue proliferation. However, there is still debate on whether the success of PDT/PTT in antimicrobial and wound healing depends solely on the cytotoxic effects or also on host immune system activation. This study investigates the dependence of PDT/PTT-induced microbial apoptosis and wound healing on immune activation and macrophage phenotype transformation and highlights the significant role of macrophage phenotype transformation in improving wound healing.