| Objects:Acute infected wounds and chronic refractory wounds caused by war trauma are one of the reasons for the troop reductions and combat force weakness.The development of safe and effective wound repair materials is critical for improving the quality of war trauma treatment as well as emergency medical response capabilities.Traditional wound-healing materials take disadvantages such as single drug composition,bacterial resistance,and a shallow drug delivery depth.Therefore,it is urgent to create novel multi-functional wound repair biomaterials with efficient antibacterial,healing promoting and precise delivery capabilities to make up for the shortcomings of traditional dressings.It is also a key issue in the field of wound healing and regeneration that has to be addressed right away.Microneedles array(MNA)is a minimally invasive and painless transdermal drug delivery method that can precisely deliver drugs to the skin with micron-sized needles.Metal-organic frameworks(MOF)are novel crystalline microporous materials that self-assemble from metal ions and organic ligands to serve as drug delivery carriers,performing catalytic,antibacterial,and healing activities.In this paper,in order to combine the advantages of MNA and MOF,Zinc-based metal-organic frameworks(Zn-MOF)with antibacterial action and copper-based metal-organic frameworks(Cu-MOF)with controlled release of nitric oxide(NO)under near-infrared irradiation(NIR)are loaded into needle tips,respectively.They are used to promote wound healing and regeneration in both acute infection wounds and chronic refractory wounds.These new biomaterials also provide the army with important technical assistance in improving its medical support capability to deal with a variety of combat missions.Methods:1.Preparation and characterization of MOF encapsulated microneedles patches:By using template replication and UV-curing method,two types of MOF encapsulated microneedles patches were prepared:ZIF-8@MeHA-MNA(ZMMN)and NO@HKUST-1@GO-MNA(NHGMN),respectively.The morphology and elemental content of MOF were characterized by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The structure of MOF were characterized by Fourier transform infrared spectroscopy(FTIR)and X-ray diffractometer(XRD).The structural properties of MOF were analyzed by Brunner-Emmet-Teller(BET)measurement and thermogravimetric analyzer(TGA).The mechanical properties of the MNA were characterized by electronic material machine and confocal laser scanning microscope.2.In vitro experiments to confirm the antibacterial capacity of ZMMN,NO controllable release capacity of NHGMN and their biocompatibility:the antibacterial ability of ZMMN was studied by co-culturing Zn-MOF nanoparticles with bacteria.Griess assay was used to assess photothermal regulated nitric oxide(NO)release of NHGMN.The biocompatibility of MOF encapsulated microneedles patches were tested by MTT and CCK-8 tests.3.In vivo experiments to verify the wound repair effect of the MOF encapsulated microneedles patches:The healing effects of ZMMN and NHGMN on acute infection wounds and chronic refractory wounds were evaluated respectively.Then,H&E staining and Masson staining were used to evaluate the wound healing effect of the MOF encapsulated microneedles patches.Finally,immunohi stochemi stry and immunofluorescence staining were performed to evaluate the expression level of inflammation(IL-6),CD 163+M2 macrophage quantity,and the vascularization degree(CD31 and α-SMA).They were carried out to evaluate the healing effects of ZMMN and NHGMN on different types of wounds,and to explore their molecular mechanisms for promoting wound repair.Results:1.Preparation and characterization of MOF encapsulated microneedles patches:Zn-MOF nanoparticles and Cu-MOF microparticles prepared by hydrothermal method possessed uniform particle size and stable crystal structure.ZMMN and NHGMN prepared by template replication and photocuring methods were characterized with neatly arranged needle tips and satisfactory mechanical strength.The MOF particles were evenly distributed inside the needle tips,allowing them to penetrate the wound for deep drug delivery.2.Antibacterial ability of ZMMN,NO controllable release ability of NHGMN and biocompatibility evaluation:Zn2+released from Zn-MOF nanoparticles can destroy the integrity of bacterial capsules,catalyze the production of oxygen free radicals to exert good antibacterial action without bacterial resistance.The antibacterial rates of Zn-MOF nanoparticles against S.aureus and E.coli were near to 50%when the concentration of Zn-MOF nanoparticles exceeded 3 mg/mL,according to the results of in vitro antibacterial experiments.In addition,the Cu-MOF microparticles encapsulated in the needle tips possessed good photothermal responsiveness ability under NIR,and the temperature of NHGMN can be rapidly raised to the working temperature within 5 min.As a result,NO molecule can be controlled released under thermal excitation for wound healing.The viability of the NIH-3T3 cells co-cultured with MNA was close to 80%as determined by the MTT and CCK-8 methods.It is expected that it will be applied for the healing and regeneration of acute infection wounds and chronic refractory wounds.3.In vivo evaluation of MOF encapsulated MNA on wound healing:The wound closure rate of ZMMN treatment group was close to 90%in the first 9 days,according to the experimental results of acute infection wound repair.Histopathology and Masson staining showed better healing effect of neonatal epithelial tissue and higher collagen content.The expression of CD31 and α-SMA in neonatal skin tissues is significantly increased by ZMMN treatment,implying that ZMMN promotes angiogenesis.In addition,ZMMN treatment can also increase the quantity of M2 macrophages while decrease the expression of inflammatory factor(IL-6),implying a potent anti-inflammation effect.The wound closure rate of NHGMN+NIR treatment group was close to 99%in the first 13 days,which was significantly greater than that of other treatment groups,according to the experimental results of chronic refractory wound repair.Histological analysis showed that the NHGMN+NIR treatment group had the best epithelial tissue reconstruction effect and the largest collagen deposition amount,indicating the best healing efficacy.In addition,the NHGMN+NIR treatment group could significantly increase the expression level of CD31 and α-SMA in wound tissue,suggesting the angiogenesis effect.The increased number of M2 macrophages and lower expression of inflammatory factors(IL-6)suggested that NHGMN+NIR treatment had a prominent anti-inflammation impact.These results fully demonstrated that ZMMN and NHGMN possessed wonderful wound healing effects in acute infected wounds and chronic refractory wounds,respectively.Conclusion:Two types of MOF encapsulated MNA,ZMMN and NHGMN,can significantly promote the healing process of acute infection wounds and chronic refractory wounds,respectively.The promoting effect of ZMMN on the repair of acute infection wounds may be related to the significant antibacterial ability of Zn-MOF nanoparticles as well as the moisturizing and repairing effects of degradable MeHA hydrogels.The promoting effect of NHGMN on the repair of chronic refractory wounds may be attributed to the controllable release of NO molecules under NIR,which is related to the anti-inflammatory,pro-angiogenic,and pro-healing abilities.The new forms of MNA have made up for many deficiencies of traditional wound dressings,providing unique concepts for the treatment of complex wounds on the battlefield. |
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