Construction Of A Novel Mangiferin Nano-delivery System And Its Application In Targeted Therapy Of Type Ⅰ Diabetes Mellitus

Diabetes mellitus（DM）is a chronic metabolic disease that generates when the body cannot take full advantage of insulin it produces,or when the pancreas is no more able to make insulin,and has become one of the most challenging public health problems today.Significant and sustained hyperglycemia causes all kinds of complications.The symptoms of absolute insulin deficiency due to destruction of pancreaticβ-cell in patients with type 1diabetes are pronounced and currently incurable.However,none of the existing clinical drugs could prevent the function decline of isletβcells.Mangiferin（MGF）,also known as Wanzhimuning,is a kind of yellowish needle-like flavonoids with molecular formula C₁₉H₁₈O₁₁ and molecular weight 422.34.It is mainly found in the flower and leaf of iris,gentiana of the gentiana family,fruit,leaves,and bark of a mango plant in the sumac family,rhizome of anemae of Liliaceae,etc.It has a wide range of pharmacological activites such as anti-inflammatory,antibacterial,anti-cancer and cough suppressant,especially anti-diabetic effects.However,MGF belongs to the BSC IV class,and its poor solubility and low enrichment in islets limit its clinical application and development.In this study,targeted polymeric nanoparticles based on mangiferin were constructed,aiming to address the defects of mangiferin and achieve precise delivery,efficient enrichment,and enhanced therapeutic efficacy.PEG acts as a macroinitiator and triggered the synthesis of PCL;Glucagon like peptide 1（GLP-1）（sequence:HAEGTFTSDVSSYLEGQAAKEFIAWLVKGRG）as an active targeting agent to the pancreas was immobilized on the block copolymer PEG-PCL to obtain final GLP-1-PEG-PCL amphiphiles（GPP）.At the same time,to avoid the toxic side effects caused by the positively charged carrier material,DMA was attached to PEG-PCL,flipping the charge to obtain the negatively charged DMA-PEG-PCL amphiphiles（DPP）.MGF were loaded into the GDPP consisting of GPP and DPP,resulting in MGF/GDPP polymeric nanoparticles,which were missile-like targeted towards pancreas for improving the accumulation and efficiency of MGF in pancreas.The intermediates and final amphiphiles were characterized by time-of-flight mass spectrometry（MALDI-TOF MS）,nuclear magnetic resonance hydrogen spectroscopy（¹H NMR）and gel permeation chromatography（GPC）.The synthesis of PCL（block molecular weight 5k）was initiated by hydroxyl group under the premise of adding Boc protection for amino group.¹H NMR calculation showed that the graft rate of GLP-1 was 17.8%,and GPC also confirmed the successful preparation of the final amphiphiles.MGF/GDPP nanoparticles were prepared by dialysis with a particle size of 158.9±1.7 nm and a negative potential for good steady state in circulation（-10.7±0.2 m V）.The transmission electron microscopy results showed that the particles were uniform in size and distribution.The MGF loading capacity was up to 6.9%±0.6%,which had drug release and good stability.The hemolysis test,material toxicity test and H&E staining test all demonstrated that the polymeric carrier material has good biosafety and biocompatibility without obvious toxic side effects.GLP-1 acts as the missile vanguard via the highly expressed GLP-1 receptor on the surface of the pancreas for improving the accumulation and efficiency of MGF in pancreas,the hypoglycemic effect of MGF and the restorative effect on pancreatic islets for NOD mice were investigated.The results of in vivo biological evaluation showed that MGF could reduce blood glucose level,improve insulin level and enhance the body’s sensitivity to glucose,and MGF/GDPP was more effective.In vivo imaging system of small animals,it could be observed that MGF/GDPP drug delivery system has better tissue targeting,and MGF is more likely to accumulate in pancreas,which improves drug utilization rate.Compared with free MGF,MGF/GDPP nanoparticles could significantly increase the proliferation ofβcells and reduce the apoptosis ofβcells,thus playing a role in islet repair in the immunofluorescence double-staining experiments,histopathology sections and immunoprotein blotting experiments.The polymer-targeted drug delivery system constructed in this study provides a novel strategy and promise for improving the administration and anti-diabetic efficacy of MGF.