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Rhein(RH,4,5-dihydroxyanthraquinone-2-carboxylic acid),an anthraquinone derivative extracted and separated from Rheum palmatum L.,R.tanguticum Maxim.ex Balf.and other traditional Chinese herbal medicines,was well known for the anti-nephropathy therapy [1] and diabetic nephropathy remedy to some degree in China,Japan and Korea [2],attracted research interests due to its various pharmacological properties.However,applications were limited by the poor solubility,low bioavailability and less distribution to kidney.In this study,we devised RH-loaded nanoparticles,comprised of the polyethylene glycol-co-polycaprolactone-co-polyethyleneimine(PEG-PCL-PEI)triblock amphiphilic polymers,and evaluated physiochemical properties and biological characteristics in vitro/vivo.Briefly,PEI was introduced to PEG-PCL via Michael addition reaction and ring-opening polymerization.The structure of PEG-PCL-PEI conjugates was confirmed by 1H NMR.The molecular weight and polydispersity indexes were characterized by gel permeation chromatography.An emulsion-solvent evaporation method was applied to carry out self-assembly PPP-RH-NPS nanoparticles.Several key performances including size,zeta potential,encapsulation efficiency and drug loading content were considered to optimize prescription.Also,pharmaceutics profile in vitro was investigated.By using dialysis method to investigate in vitro release characteristics,selecting the rabbit red blood cells to evaluate the hemolysis rate and MTT method to estimate the cytotoxicity on HK-2 cells.Flow cytometry instrument to investigate the uptake efficiency,confocal microscope to observe the mechanism and cell distribution of PPP-RH-NPS labeled by Cy5 fluorescent probe.Results showed that molecular weight of PEG-PCL-PEI polymer was 9.5KD.The critical micelle concentration(CMC)was 0.723 mmol/l determined by pyrene fluorescence method.Remarkably,PPP-RH-NPS were visualized homogeneously spherical structure with a desirable size and narrow distribution.The yellow emulsions were formed with a size of 118.3±3.6 nm,a PDI of 0.19±0.08 and a zeta potential of 6.3±1.5 mV.Relatively high entrapment efficiency(93.64±5.28%)and drug loading content(8.57±0.53%)were achieved.In addition,the accumulative release rate(Q)of PPP-RH-NPS in PBS(pH 7.4)was 75.92%in 48 h,and the release profile satisfied well to Higuchi Q vs t1/2 model(Q=0.1216t1/2+0.0695,R2=0.8874).Furthermore,within the scope of the 0-0.05 mmol/l,PPP-RH-NPS exhibited no obvious hemolysis on rabbit erythrocyte(RRBC)and toxicity on HK-2 cells.PPP-RH-NPS accompanied by fast lysosomes escape ability could enter cells quickly and fully internalize within 30 minutes.In DN model mouse,the PPP-RH-NPS can target distribute to diseased kidney and improve the fluorescence intensity in kidney.In conclusion,we synthesized the PEG-PCL-PEI polymer and developed PPP-RH-NPS successfully.PPP-RH-NPS possessed uniform particle size,higher encapsulation efficiency and drug-loading rate,control-release characteristics,enhanced uptake and internalization,endosomal escape property,good biocompatibility and kidney targeting property.PPP-RH-NPS will be a promising pharmaceutical formulation for further research on kinds of nephropathy.