Bismuth Tungstate-Silver Sulfide Z-Scheme Heterostructure Nanoglue Promotes Wound Healing

Rapid wound closure and bacterial inactivation are effective strategies to promote wound healing.Here,Bismuth tungstate（Bi₂WO₆）-silver sulfide（Ag₂S）direct Z-heterostructure multifunctional nanogel（BWOA NPs）was designed to accelerate wound healing.BWOA NPs’hollow structure and rough surface could effectively close wound tissues acting as a barrier between external bacteria and the wound,preventing bacterial invasion.More importantly,the unique Z-scheme heterostructure endows BWOA NPs with an efficient electron-hole separating ability and retains strong redox capacity.The separated electrons and holes react with water and oxygen,respectively,to efficiently generate reactive oxygen species（ROS）that can be used to remove bacteria from wound tissue.Therefore,under the combined action of the two,BWOA NPs can effectively accelerate wound healing.Specific research results are as follows:1.Synthesis of BWOA NPs and formation of Z-scheme heterostructures:BWOA NPs were obtained by in-situ growth of silver sulfide on the surface of bismuth tungstate hollow nanoparticles prepared by a two-step hydrothermal method.X-ray diffraction and X-ray photoelectron spectroscopy showed that the direct Z-scheme heterostructure of BWOA was successfully prepared.Scanning and transmission electron microscopy images and corresponding elemental scanning analysis showed that bismuth tungstate showed a rough hollow structure with silver sulfide growing on its surface.The band gap width,valence band and conduction band positions of bismuth tungstate and silver sulfide were characterized by UV-Vis diffuse reflection spectrum,X-ray photoelectron spectroscopy and Mott-Schottky curve.The results confirmed that the contact between bismuth tungstate and silver sulfide would generate an internal electric field and form a direct Z-scheme heterostructure.Photoluminescence,electrochemical impedance spectroscopy and photocurrent measurements show that BWOA direct Z-scheme heterostructure has excellent photoinduced electron and hole separation ability.2.BWOA NPs accelerated wound closure ability:BWOA NPs nanogel was attached to two pieces of mouse skin to test the tissue adhesion ability.The force-displacement curve of the lap shear adhesion test showed that BWOA NPs had strong adhesion ability and could rapidly close the wound.The hemostasis of BWOA NPs was verified in the mouse tail amputation model,and the adhesion of BWOA NPs to the wound in vivo was also verified in the mouse back cut wound model,and the risk of bacterial infection was reduced due to the reduced exposure time of the wound.3.Sunlight-Triggered ROS Generation and Antibacterial Activity of BWOP Z-Scheme Heterostructure NPs:Due to the high efficiency of electron hole pair separation,BWOA NPs can produce ROS efficiently.The reactive oxygen generation capacity of BWOA NPs was detected by dimethoxazole yellow colorimetry（XTT）,aminophenylfluorescein probe（APF）and electron spin resonance（ESR）.The results showed that BWOA NPs had excellent ROS generation ability under simulated sunlight,and the ROS produced were O₂·^-and·OH.Encouraged by the excellent ROS production capacity detected,the antibacterial activity of BWOA NPs against Gram-negative E.coli and S.ureus was investigated.The results showed that the inhibition rates of BWOA NPs on E.coli and S.ureus were 61.62±2.85 and 73.40±3.28%,respectively,under sunlight irradiation.The results were further verified by bacterial coating and bacterial staining.The ROS levels in bacteria were analyzed by fluorescence probe DCF method and glutathione levels were detected by DTNB method.It was concluded that BWOA NPs caused strong oxidative damage to bacteria through ROS,leading to bacterial inactivation.4.The ability of BWOA NPs to promote wound healing:Before carrying out animal experiments,the biosafety of BWOA NPs was verified by hemolysis experiment and MTT cytotoxicity detection,and the results all showed that the excellent biocompatibility of BWOA NPs.The wound healing was observed and the wound healing rate was statistically analyzed through the wound administration treatment and the simulation of sunlight exposure in different groups.The results showed that the wound healing rate of mice in the simulation of sunlight exposure was 25.90±5.85%higher than that in PBS.At the same time,combined with tissue H&E staining and Masson staining analysis,it was found that on the 8th day of healing,the wound space was obviously narrowed and the wound surface was almost completely connected.BWOA NPs could effectively accelerate wound healing.In conclusion,BWOA direct Z-scheme heterostructural nanomaterials can be used as a multifunctional nanogel,which has great potential in accelerating the wound healing process due to its ability to rapidly close wounds and inactivate bacteria.