| Objectives:In order to overcome blood-brain barrier in the chemotherapy of brain metastases,we designed a brain metastases targeting drug delivery system that up-regulate and target low density lipoprotein receptor-related protein 1(LRP1)of brain microvascular endothelial cells(BMECs)and effectively overcome blood-brain barrier.Poly(lactic-co-glycolic acid)-poly(?-carbobenzoxyl-L-lysine)(PLGA-PLL),is the starting material.We prepared doxorubicin(DOX)and simvastatin(SIM)-loaded and Angiopepe-2-modified nanoparticles(NPs)(S@A-NPs).We explored S@A-NPs/DOX enhance brain accumulation and targeting efficiency of brain metastases of DOX,and evaluated the therapeutic effect of S@A-NPs/DOX on mouse bearing brain metastases.Methods:(1)S@A-NPs/DOX was prepared by the double-emulsion solvent evaporation technique.The physicochemical eharacterization of NPs was investigated by dynamic light scattering and transmission electron microscopy.Meantime,drug release was studied.(2)The effects of SIM on the uptake of A-NPs/DOX on BMECs were investigated.The optimum drug loading of S@A-NPs was screened.The effect of SIM on LRP1 expression of BMECs was investigated by immunoofluorescence.(3)In normal mice,the effect of SIM on brain accumulation of A.NPs was investigated with IR780 as indieator:the self-promoting effect of S@A-NPs was further investigated.The effect of S@A-NPs on LRP1 expression in brain microvessels was investigated by immunofluorescence.(4)The effects of SIM on the uptake of A-NPs/DOX on brain metastatic tumor cells(BMTCs)were investigated.The effect of SIM on LRP1 expression of BMTCs was investigated by immunofluorescence and western blotting.(5)The distribution of DOX in brain metastases of mice with different pretreatment was studied by frozen sections.The effect of S@A-NPs on LRP1 expression of brain metastases was investigated by immunofluorescence.The pharmacodynamics of S@A-NPs/DOX was investigated on mice bearing brain metastases.Results:(1)Physicochemical characterization showed the size and zeta potential of S@A-NPs/DOX is 104±4.1 nm and-3.6±0.6 mV,respectively.The co-encapsulation of SIM did not effect the morphology and particle size of NPs.DOX release of S@A-NPs/DOX displayed a pH-dependent release manner,while SIM release showed pH-independent release pattern.(2)Free SIM promoted the uptake of A-NPs/DOX on BMECs in a time-dependent manner.S@A-NPs with 8.6%drug loading was chosen to prepare NPs.Free SIM and S@A-NPs could up-regulate LRP1 expression of BMECs.(3)In normal mice,SIM could increase the accumulation of NPs and A-NPs in the brain.S@A-NPs had the self-promoting effect.S@A-NPs could significantly increase the expression of LRP1 in brain microvessds.(4)Free SIM and S@A-NPs promoted uptake of A-NPs/DOX on BMTCs in a time-dependent manner.Free SIM and S@A-NPs could promote LRP1 expression of BMTCs.(5)In mice bearing brain metastases,the accumulation of A-NPs/DOX in normal brain and brain metastases was higher than that of free DOX and NPs/DOX.And,free SIM enhanced the accumulation of A-NPs/DOX in normal brain and brain metastases.Pre-treatments of S@A-NPs mainly enhanced accumulation of A-NPs/DOX in brain metastases.When S@A-NPs and A-NPs/DOX were administered together,the co-localization of DOX and brain metastases was significantly higher than that of free DOX alone.S@A-NPs could significantly up-regulate the expression of LRP1 in brain metastases.S@A-NPs/DOX could significantly prolong the median survival of mice bearing brain metastases.Conclusions:In this study,we successfully constructed a target drug delivery system S@A-NPs/DOX for brain metastases based on LRP1 up-regulation of SIM,which could promote A-NPs to penetrate blood-brain barrier and target brain metastases.It is expected to provide a new method for the treatment of brain metastases. |
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