Guangye Ge,Lijuan Wu,Fenglan Zhang,Tianyi Wang,Lei Han,Xiaoying Kong,Jinsheng Shi
In recent years, photodynamic therapy (PDT) or chemodynamic therapy (CDT) based on the antimicrobial property or anti-biofilm property of reactive oxygen species (ROS) have been widely recognized for their low susceptibility to microbial resistance. However, due to the complication of the three-dimensional structure of the biofilm at the wound site and the high quenching rate of common ROS, the treatment with traditional ROS could not achieve satisfactory wound healing effects. Here, Na 2 S 2 O 8 @ZIF-67/GOx nanoparticles (NZG NPs) were prepared as a new high-toxic ROS nanogenerator for application of biofilm-infecting wound healing with the assistance of glucose oxidase (GOx) for amplified CDT and immune activation. When the NZG NPs entered the biofilm, Co-based metal organic frame (ZIF-67) ruptured in the acidic microenvironment, which induced the release of GOx and the production of gluconic acid and H 2 O 2 , further promoting the decrease of pH of the biofilm microenvironment and in turn accelerating the cleavage of ZIF-67 and the release of Na 2 S 2 O 8 . Then, S 2 O 8 2− could gradually transformed into high-toxic sulfate radical ( SO 4 − ), part of which further produced OH in situ with H 2 O, thereby inhibiting the proliferation of bacteria and biofilms. Interestingly, these two types of ROS not only caused direct damage to the biofilm, but also activated the immune system of the wound site as well as the body more effectively, which also played an indirect role in promoting biofilm destruction and wound healing. In vitro and in vivo results showed that, as a new high-toxic ROS nanogenerator, the NZG NPs supply amplified chemodynamic therapy and immune activation to destroy biofilms, but also achieve effective wound healing without causing bacterial tolerance, which provides a new strategy for the development of biofilm-infecting wound healing.
There are plentiful ways to synthesize sulfidized nanoscale zerovalent iron (S-nZVI), and this study investigated the influence of sulfur reagents (Na 2 S, Na 2 S 2 O 3 , Na 2 S 2 O 4 ) and sulfidation sequence (co-sulfidation and post-sulfidation method) on the physicochemical properties, reactivity, and long-term performance of S-nZVI in simulated groundwater. The results suggested that the co-sulfidized nZVI (S-nZVI co ) has higher reactivity (∼2-fold) than S-nZVI post due to the stronger electron transfer capacity, deriving from the higher content of Fe 0 and reductive sulfur species. However, during aging, the reactivity of S-nZVI co would be lost more rapidly than S-nZVI post , due to the faster corrosion of Fe 0 and more oxidation of reductive sulfur species. S-nZVI post has the superior long-term performance with the degradation rate of trichloroethylene (TCE) remained at 30%∼60% even after 90 d of aging. Sulfur precursors can control the selectivity of S-nZVI by affecting the sulfur speciation on the particle surface. The proportion of reductive sulfur species on S-nZVI post synthesized by Na 2 S was higher than S-nZVI post synthesized by Na 2 S 2 O 3 or Na 2 S 2 O 4 , resulting in a higher selectivity of the former S-nZVI post than the latter S-nZVI post . In addition, sulfidation procedures and sulfur precursors did not affect the degradation pathway of TCE. Nevertheless, the degradation product distribution can be affected by the different physicochemical transformation of various types of S-nZVI with the aging time. These results indicated that sulfur reagents and sulfidation procedures have crucial effects on the reactivity and long-term performance of S-nZVI, which can be designed for the specific application scenarios.
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