Structural,Enzyme-like Properties Of Pt/CeO₂ Single-Atom Nanozyme And Application In Traumatic Brain Injury

Similar to the catalytic mechanism of natural enzymes,nanozyme exhibits good catalytic performance.Moreover,nanozyme is widely used in biological fields due to its simple synthesis methods and stable catalytic activities.Especially,nanozyme has been attracted more and more attention on the treatment of oxidative stress-related diseases.This paper mainly focuses on the treatment of traumatic brain injury with nanozyme.As one of the most serious injuries,traumatic brain injury can trigger a series of biochemical reactions and neuro-immune responses around wound,thus inducing irreversible nerve tissue damage and seriously endangering the life of the injured.However,the limitation of administration methods such as tail vein injection and gavage,causes serious side effects and low drug utilization rate during the treatment of traumatic brain injury.Therefore,we designed a nanozyme-based bandage with single-atom catalysis for noninvasive therapy of traumatic brain injury.The physical structure,enzyme-like activities and free radical scavenging abilities of the single-atom nanozyme were tested and analyzed in detail.The therapeutic effect and principle of the single-atom nanozyme-based bandage for traumatic brain injury were further studied.The main research contents are as follows:（1）CeO₂ nanozyme was synthesized by a simple aqueous phase method.Pt/CeO₂ single-atom nanozyme was further obtained with higher catalytic activities.First,the samples were characterized using several different physical methods.The results show that Pt is atomically dispersed on facets and induces an obvious lattice expansion of CeO₂ nanozyme,indicating the formation of a new stable active site and electron transfer path in Pt/CeO₂ nanozyme,which leads to changes in its catalytic activity.Second,the catalytic properties of the samples were tested and analyzed by chemical means.The study manifests that multiple enzyme-mimetic activities and scavenging capability against free radicals of single-atom Pt/CeO₂ nanozyme are 2-10times and 3-10 times higher than those of CeO₂ nanozyme respectively.Finally,the density functional theory was utilized to analyze the single-atom Pt/CeO₂ nanozyme system,and the calculated results were consistent with the experimental results.（2）Cell experiments were conducted to test the free radical scavenging abilities and anti-inflammatory abilities of the nanozyme.First,toxicological experiments reveal scarcely any cytotoxicity of the nanozyme.Second,the single-atom Pt/CeO₂nanozyme is proved to protect cells better against free radical damage than CeO₂nanozyme.Finally,the single-atom Pt/CeO₂ nanozyme also possesses excellent anti-inflammatory abilities in vitro.（3）Furthermore,the nanozyme-based bandages were designed by nanozyme loaded onto the flexible carbon fiber cloth,which were applied to further treatment of traumatic brain injury.First,the catalytic performance of nanozyme-based bandages were tested by enzyme-like experiments.The results show that the nanozyme-based bandages retained the durable catalytic activity without obvious decay during the one-month test,indicating the good activity and stability of the single-atom nanozyme-based bandage.Second,animal experiments reveal that the single-atom nanozyme-based bandage did show a significant effect in the treatment of traumatic brain injury.The single-atom nanozyme-based bandage can not only promote wound healing effectively,but also reduce nerve inflammation and relieve nerve injury efficiently.