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Advanced Materials:Z Photodynamic therapy of oxygen self supply in space-time synchronization based on nano heterostructure

wallpapers News 2020-11-25
The rapid proliferation of

tumor cells the uneven development of blood vessels often lead to the lack of oxygen (O2) supply in tumor the formation of hypoxic microenvironment which greatly limits the generation efficiency of reactive oxygen species (ROS) of photosensitizers in the process of photodynamic therapy (PDT) which greatly reduces the treatment efficiency of hypoxic tumors. At present a variety of O2 delivery or generation strategies have been used to compensate the oxygen consumption of photosensitizers. However due to the limited saturation slow migration characteristics of O2 in tumor tissues these strategies still can not meet the oxygen dem of photosensitizers in time space.

researcher Zhang Haiyuan of Changchun Institute of Applied Chemistry Chinese Academy of Sciences has designed bismuth sulfide (Bi2S3) - bismuth (BI) Z-type heterostructure to solve this problem which can achieve spatiotemporal synchronous ROS generation self supply of O2 at the level of single nanoparticles under near-infrared light irradiation providing a new strategy for efficient PDT treatment of deep tissue hypoxia tumor. The results show that when the oxidation potential of the valence b hole is greater than that of water (1.23 V relative to the stard hydrogen electrode) the hole will react with water to produce O2 while the reduction potential of the conduction b electron is less than that of superoxide anion (- 0.13 V) 5) When the b gap is less than 1.53 EV electrons may be excited by near-infrared light (808 nm) to generate electrons holes. Therefore nano materials with conduction b position lower than - 0.13 V valence b position higher than 1.23 V b gap width less than 1.53 EV are likely to realize the spatiotemporal synchronous generation of O2 ROS excited by near-infrared light. The unique b characteristics of Bi2S3 Bi enable them to form a Z-type heterostructure which satisfies the above three conditions simultaneously. Because the Fermi energy level of Bi is higher than that of Bi2S3 electrons will flow from Bi to Bi2S3 a built-in electric field will be generated at the interface during equilibrium from Bi to Bi2S3. Under the excitation of 808 nm near-infrared light the photogenerated electrons in the conduction b of Bi2S3 will transfer from Bi2S3 to the surface of Bi under the driving of internal electric field compound with the photogenerated holes in the valence b so that the Bi2S3 valence b holes Bi conduction b electrons are separated have strong redox energy. In fact when the biocompatible modified Bi2S3 Bi nano heterostructure is injected into the tumor tissue of tumor bearing mice via tail vein near-infrared light irradiation can weaken the hypoxic condition of tumor microenvironment produce strong oxidative damage to tumor tissue showing a good therapeutic effect of PDT for hypoxic tumor.

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