Construction of photo-responsive nanomaterials and their application in multidrug-resistant bacteria-infected wounds therapy

Abstract

Wound infections pose an enormous burden to public health and global economics. A daunting challenge in treating infected wounds is the increasing prevalence of multidrug-resistant (MDR) bacteria strains that show resistance to clinical antibiotics. The high lethality of the strains makes them particularly dangerous for public health. At present, promoting tissue regeneration while rapidly eliminating infection still remains a challenge, and new strategies are needed urgently.

With the application of nanoparticles in biomedicine, the reactive oxygen species (ROS)-based nanomaterials have attracted extensive attention for tissue infection. Among them, a series of photocatalytic nanoparticles have been developed as photosensitizers for antibacterial photodynamic therapy (aPDT). However, their applications are still limited due to unsatisfactory photodynamic antibacterial efficiency and biocompatibility. The strategy of constructing heterojunctions has therefore been successfully introduced to improve the photodynamic antibacterial effect. In addition to the well-known antibacterial effects, ROS also play an important regulatory role in angiogenesis. With the advantage of photo-excited ROS generation, heterojunction nanomaterials can potentially be used for angiogenesis.

Here, a novel photo-responsive Z-scheme heterojunction (BiOCl/Ag3PO4) was developed for the MDR bacteria-infected wounds therapy. With the strong interfacial interaction and staggered band alignment between the BiOCl and Ag3PO4, an internal electric field in the Z-scheme heterojunction was built, which realized efficient interfacial charge-carrier separation and transfer for enabling efficient photo-responsive generation of ROS. The Z-scheme change-transfer route mechanism for ROS generation was supported by the photo-electrochemistry measurements, the electron paramagnetic resonance spectra and the density functional theory calculations. Additionally, the photo-responsive ROS generation levels of the BiOCl/Ag3PO4 Z-scheme heterojunction could be modulated by regulable light.

The BiOCl/Ag3PO4 Z-scheme heterojunction presented an outstanding antibacterial activity with an antibacterial rate of 95.3% in 3 min under the illumination of 1.5 W/cm2, surpassing many reported BiOCl-based photo-responsive nanomaterials. Meanwhile, it was surprisingly found that the angiogenesis-related gene expression in human umbilical vein endothelial cells could be upregulated by BiOCl/Ag3PO4 heterojunction when the light intensity was reduced to 0.5 W/cm2. The results demonstrated that the BiOCl/Ag3PO4 Z-scheme heterojunction achieved the bio-functional transformation from rapid sterilization to angiogenesis through regulable illumination, which accelerated the healing of infected wounds. The developed strategy of integrating the property of the photo-responsive nanomaterial and the biological effect of ROS may provide a new perspective for the clinical treatment of MDR bacteria-infected tissue.