| Traumatic spinal cord injury（SCI）is a highly destructive disease.After spinal cord injury,a large amount of ROS is produced in the spinal cord microenvironment,leading to a series of pathological and physiological changes,which brings great difficulties and obstacles to the treatment of spinal cord injury.However,when spinal cord injury occurs,the wound infected with bacteria will become difficult to heal and produce a series of complications,such as suppurative infection,swelling,suppurative Myelitis,which greatly increases the difficulty of treating traumatic spinal cord injury.Therefore,while treating spinal cord injury,antibacterial treatment of wound infection is also necessary to achieve the goal of efficient treatment of spinal cord injury.ROS mediated treatment strategy is a potential strategy that can significantly reduce the significant adverse reactions associated with spinal cord injury,but currently used treatment methods in clinical practice often come with serious side effects such as gastric bleeding and intestinal spasms.With the research on antibacterial treatment of bacterial infections,photodynamic sterilization has received increasing attention due to its minimal side effects,and has now become a highly promising antibacterial strategy.Based on this,we have constructed a strategy that not only utilizes the anti-inflammatory ability and good biocompatibility of nanozymes to treat spinal cord injury,but also utilizes their photodynamic bactericidal properties to antibacterial and promote wound healing.In this paper,we developed a zinc pyrogallic acid（PA-Zn）nanozyme with a structure similar to that of superoxide dismutase to treat injured spinal cord,in which zinc,as a metal center,is coupled with pyrogallic acid through the Zn-O-C bridge to form a zinc four coordinated structure.Among them,PA-Zn can simulate the enzyme like activity of superoxide dismutase（SOD）and catalase（CAT）to treat injured spinal cord.At the same time,due to its unique photosensitizer characteristics,PA-Zn can effectively suppress bacterial infections under visible light irradiation.It mainly includes the following aspects:1.Due to its excellent ROS regulation ability,nanozymes have been widely studied and applied in the treatment of ROS related diseases.Based on this,we have developed a sheet like zinc pyrogallic acid nanozyme（PA-Zn）with good biocompatibility.Through various enzyme activity tests,it was determined that the nanozyme had the double enzyme activity of CAT and SOD and the ability to eliminate other types of free radicals.Meanwhile,In vitro tests demonstrated that PA-Zn could efficiently inhibit the expression of ROS and M1-related markers（IL-1β）,and upregulate the expression of M2-related markers（Arg-1）.Furthermore,PA-Zn could significantly promote ventral horn neurons survival and locomotor functional recovery in vivo,while inhibit injured spinal cord damage,and decrease the infiltration of macrophages in the lesion.PA-Zn had a better therapeutic effect on SCI animals at extremely low dosage(0.1 mg kg-1)and shorter time（2 weeks）.The working dosage of PA-Zn was even 100-fold lower than some previous reported nanomedicines for SCI treatment.2.In order to further explore the ability of PA-Zn to be applied in the antibacterial treatment of major trauma,its antibacterial properties were studied.After a series of antibacterial experiments in vitro,it has been proven that under visible light illumination,50μg m L-1PA-Zn can clear over 90%of the extended-spectrumβ-lactamases producing Escherichia coli（ESBL-producing E.coli）and methicillin-resistant Staphylococcus aureus（MRSA）,which verifies that PA-Zn has significant antibacterial performance against both bacteria.The wound healing experiment in a mouse model further confirms the high antibacterial activity and good biocompatibility of PA-Zn in promoting wound healing. |
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