Study On Kidney Function Injury And Functional Group Surface Modifications Influence On The Renal Accumulation And Distribution Of Nano-drug Delivery System

Background and objective:The development of nanotechnology sheds light on treatment of disease,because nanoparticles（NPs）improve pharmacokinetics and immunogenicity on a given agent and facilitate the targeted drug delivering to specific parts for reducing systemic toxic and side effects.The metabolism of nano-drug delivery system in vivo is of great significance to fate and biosafety in vivo.Kidneys are an important metabolic organ of body and one of the main metabolic pathways of nano-drug delivery system.Surface characters of nano-drug delivery systems have a significant impact on their fate in vivo,as well as their metabolism in kidneys.Functional group surface modifications can improve the circulation time and distribution of nano-drug delivery system in vivo,but their effect on the metabolic process of nano-drug delivery system in kidneys remains unclear.In addition,the changes of renal physiological function also have an important effect on the metabolic process of nano-drug delivery system.However,the physiological structure and function of kidneys are susceptible to effects of aging,drug toxicity and other conditions,resulting in renal injury,thereby affecting their metabolic capacity.What’s more,it is not clear whether renal injury affects the renal metabolic process of nano-drug delivery system.Will it most likely influence the renal accumulation and distribution of nano-drug delivery systems.In conclusion,the project studies the effects of renal function damage and surface functional group modification on renal metabolism of nano-drug delivery systems will provide theoretical support for improving the metabolic kinetic characteristics of nano-drug delivery system in vivo,enhancing the accumulation of target sites,and improving the therapeutic effect.Methods:We established mice models with different stages of AKI by intraperitoneally injecting the same dose of（17.5 mg/kg）.Detected the creatinine of the collected blood samples through the creatinine kit,and defined the stages of AKI according to the creatinine level.Through assessment of kidney/body weight ratio,changes in kidneys and score of renal lesions supported the results of classification.The kidneys of different stages of AKI were embedded in paraffin and sections,so as to study the specific changes of the kidneys under different stages of AKI.Subsequently,we used emulsion-solvent evaluation technology to prepare NPs with different functional group surface modifications,and labeled by fluorescent dye（DID）to facilitate the study of their distribution in mice.It was measured at 25℃ by using dynamic light scattering（DLS）to the size and potential of these NPs with different functional group surface modifications.In order to study the effects of functional group surface modifications on the accumulation and distribution of nano-drug delivery system in kidneys,we labeled nano-drug delivery system with different functional group surface modifications by Di D with similar fluorescence intensity,which were injected into normal mice and mice with different stages of AKI through the tail vein.The mice were euthanized 24 hours after injecting,and the kidneys were taken out and used for Ex vivo fluorescence imaging.These data were normalized and analyzed by Living Image.After that,frozen sections of kidneys were stained with AF488-Phalloidin and DAPI,and images of a confocal microscope were used to further study the distribution of NPs in kidneys.Results:1.Mice treated by cisplatin,murine models of different levels of AKI were obtained.The levels of AKI were:Acute kidney injury stage 1-2（AKI stage 1-2）,acute kidney injury stage 3（AKI stage 3）and acute kidney injury stage 4（AKI stage 4）.2.The kidneys of AKI stage 1-2 had mild vacuolar degeneration and loss of brush border.Serious damage occurred in kidneys of AKI stage 3 including vacuolar degeneration,severe loss of brush border,cell swelling and nuclear shedding.Except for the above lesions,extensive injuries also occurred in the kidneys of AKI stage 4.3.In normal mice,compared with methoxy（OMe）and NH₂,maleamide（Mal）modification significantly enhanced the accumulation of the nano-drug delivery system in kidneys.4.Renal function injury significantly changed renal accumulation of nano-drug delivery systems,and their accumulation in kidneys became stronger as the injury worsened.Mal modification enhanced the accumulation of nano-drug delivery system in kidneys with AKI stage 1-2;OMe modification enhanced the accumulation of nano-drug delivery system in kidneys with AKI stage 3;But NH₂promoted the accumulation of the nano-drug delivery system in kidney with AKI stage 4.5.In normal kidney tissues and kidneys with AKI stage 1-2,the distribution of nano-drug delivery systems in cortex was significantly higher than those of medulla,and was not affected by functional group surface modifications.In the kidneys with AKI stage 4,OMe-modified nano-drug delivery system was mainly concentrated in cortex and medulla of kidneys.6.Nano-drug delivery systems were mainly distributed in the renal tubular epithelial cells in kidneys of normal mice and renal interstitium;however,after renal function injury occurred,in addition to the above-mentioned parts,they were also distributed in the lumen of renal tubules.Conclusion:Our study confirmed that renal physiological function injury had a significant impact on renal accumulation and distribution,and with the aggravation of renal injury,the accumulation level of nano-drug delivery system in kidneys also gradually increased.Different functional group surface modifications also significantly affected the renal accumulation level of nano-drug delivery system.