Designed Fabrication Of Anti-oxidant Nanozyme-based Nanosystems For Acute Liver Injury Therapy And Diagnosis

Acute liver failure(ALF)is a clinical syndrome of severe liver function damage that occurs rapidly within days or weeks.Acetaminophen(APAP)-induced acute liver injury(ALI)is one of the main causes of ALF in many countries and regions.N-acetylcysteine(NAC)has been proven to be effective in treating APAP-induced ALI,while the therapeutic effect of NAC decreases significantly for patients with late-stage APAP-induced ALI.Therefore,the development of new drugs for the treatment of late-stage ALI or early diagnosis of ALI is of great significance.The metabolite N-acetyl-p-benzoquinone imine(NAPQI)formed by excessive APAP in the liver depletes glutathione(GSH)in liver tissue,leading to the production of large amounts of reactive oxygen species(ROS),thus inducing oxidative stress and damaging liver cells.Antioxidant enzymes,such as superoxide dismutase(SOD)and catalase(CAT),can neutralize ROS to prevent them from damaging cells and tissues,which are ideal candidates for treating ALI.Antioxidant nanozymes are a type of nanomaterial that can simulate the catalytic activities of natural antioxidant enzymes.Compared to natural enzymes,nanozymes possess higher stability,better catalytic activity,and lower cost,making them widely used in various biomedical applications.In recent years,antioxidant nanozymes have been extensively investigated in the treatment of wound,tissue injury,neurodegenerative diseases,and so on.Therefore,the design and fabrication of antioxidant nanozyme-based nanosystems are of great potential for the therapy and diagnosis of ALI.In recent years,ruthenium nanoparticles(Ru NPs)with multiple enzyme-like activities have attracted increasing attentions.However,their relatively low antioxidant enzyme-like activities,and unclear catalytic mechanism hinder their further application in the biomedical field.Here,Ru NPs with sizes of ～ 2.0 nm(s Ru NP),～ 3.9 nm(m Ru NP),and ～ 5.9 nm(l Ru NP)were synthesized by adjusting the ratio of reductant to metal precursor through a solvothermal method.As the size of Ru NPs decreases,the ratio of surface oxidized Ru increases;as the size decreased to ～ 2.0 nm,the surface oxidized Ru becomes dominant on s Ru NP and the CAT-like activity s Ru NP is markedly potentiated.Subsequently,s Ru NP is more effective than m Ru NP and l Ru NP in protecting cells from oxidative stress.Moreover,s Ru NP can sustainably ameliorate oxidative stress after intravenously injected into late-stage APAP-induced ALI mice,and perform highly efficient therapeutic efficiency on ALI mice even when treated at 6 h after APAP intoxication.Early diagnosis of ALI can help patients receive timely treatment and avoid further deterioration of the condition.During APAP metabolism,the accumulation of excessive NAPQI initially causes intracellular oxidative stress,leading to the production of large amounts of ROS,which causes the necrosis of liver cells.Therefore,ROS is one of the important and relatively early pathological changes in liver tissues after the occurrence of ALI.Herein,a ROS-sensitive photoacoustic nanoprobe(RSPN)based on antioxidant nanozyme is constructed by using ROS-sensitive amphiphilic polymer to assemble the photoacoustic imaging contrast agent zinc phthalocyanine(Zn Pc)and ceria nanozymes(Ce NZ)for the early diagnosis and treatment of ALI.After stimulated by ROS,the ROS-sensitive amphiphilic polymer in RSPN is cleaved,and thus the Zn Pc and Ce NZ are released form the RSPN.Subsequently,the released Zn Pc aggregates into large particles due to the intermolecular hydrophobic interaction and aromatic π-π stacking effect,which could generate photoacoustic signals through the nonradiative thermal deactivation pathway.At the same time,the catalytic activity of the released Ce NZ is restored,which further catalyzes ROS into oxygen bubbles to amplify the PA signals through the bubble-triggered inertial cavitation effect.After intravenously injected RSPN into ALI mice,the photoacoustic imaging signal of RSPN could be enhanced to the peak at 4 h after APAP intoxication,while ALT level reaches the peak at 12 h after APAP intoxication,indicating that the photoacoustic imaging diagnosis method based on RSPN could detect the pathological changes after ALI earlier than the clinical ALT method.Moreover,in response to ROS in injured liver tissues,the antioxidant nanozymes could be released from RSPN,which can achieve the photoacoustic image-guided ALI nanocatalytic therapy.In summary,this paper has designed a series of novel anti-oxidant nanozyme-based nanosystems for late-stage ALI treatment and early-stage ALI diagnosis.(1)The antioxidant enzyme-like activities of Ru NPs are regulated by taking advantage of the size effect of nanomaterials,and s Ru NP with excellent antioxidant enzyme-like activities is successfully designed and constructed,which can sustainably alleviate oxidative stress and thus show good therapeutic effects in late-stage ALI.(2)A ROS-sensitive photoacoustic nanoprobe(RSPN)based on antioxidant nanozyme is designed and constructed based on nanoassembly strategy.RSPN can respond to high levels of ROS produced by injured liver tissues,and thus the photoacoustic imaging signal of RSPN is amplified,which enables the earlier detection of pathological changes in ALI than clinical ALT indicators.Besides,RSPN can also simultaneously achieve nanocatalytic therapy of ALI through released antioxidant nanozyme,demonstrating good application potentials.