| Nowadays,cerebral ischemia threatens the health of many people.It is one of the medical problems to be solved urgently.The main difficulty of its treatment lies in the existence of blood-brain barrier(BBB),which limits most of the therapeutic drugs to pass through the physiological barrier and enter the brain to give full play to their efficacy.Therefore,how to overcome this technical bottleneck has become the main direction of drug delivery system research.With the in-depth study of biological nano materials,dendrimers as a new drug carrier material have come into people’s field of vision.At the same time,studies have shown that it is one of the effective methods to achieve targeted release of drugs and precise treatment by modifying nanocarriers with targeted functional peptides.Therefore,in the present work,based on these two design concepts,dendrimers are used as the basic nanocarriers of the drugs,and was modified with the target peptides to achieve targeted release.In this paper,two kinds of basic nano support materials,poly(L-lysine)dendrimer(PLLD)and polyamide amine dendrimer(PAMAM),were synthesized by divergence and convergence method.Firstly,PEG was connected to the surface of the nanocarriers to reduce its cytotoxicity by the reaction of the primary amine group at the end of the two nanocarriers with the succinimide group at the end of the bifunctional polyethylene glycol(NHS-PEG-MAL).Then,two kinds of targeted drug delivery carriers L57&PGP-PEG-PLLD and L57&PGP-PEG-PAMAM were synthesized by sulfhydryl reaction of the maleimide group at the end of NHS-PEG-MAL with the targeted polypeptide L57and PGP.In order to study the physical and chemical properties of poly(L-lysine)(PLLD)and polyamide amine(PAMAM)dendrimers,their structures,morphologies and particle sizes were characterized by FT-IR,~1H-NMR,SEM,TEM,zeta potential and particle size analyzer.The results showed that the two nanocarriers were successfully synthesized,and the particle size of L57&PGP-PEG-PLLD was 215.3±0.5 nm,which met the needs of human body.Breviscapine(Bre)delivery system was prepared by physical embedding method.The drug loading and in vitro release properties of PLLD/Bre,PEG-PLLD/Bre and dual-targeting modified nanocarriers were determined by high performance liquid chromatography(HPLC).The drug loading of L57&PGP-PEG-PLLD was16.7%.The results of in vitro release showed that the release rates of PLLD/Bre,PEG-PLLD/Bre and L57&PGP-PEG-PLLD/Bre were 89.6%,62.5%and 57.3%respectively after 72 hours,and the modified nanocarriers achieved a good sustained-release effect.The particle size of L57&PGP-PEG-PAMAM was 140.2±0.6 nm,HPLC was used to determine the drug loading and in vitro release properties of L57&PGP-PEG-PAMAM,result showed that the drug loading of L57&PGP-PEG-PAMAM was 20.12%,the release rates of PAMAM/Bre,PEG-PAMAMBre and L57&PGP-PEG-PAMAM/Bre were 89.6%,62.5%and57.3%,and the modified nanocarriers achieved a good sustained-release effect.In vivo brain targeting study confirmed that the nanocarriers were dyed with Di R fluorescent dye and injected into mice by tail vein injection.The brain targeting of the unmodified nanocarriers and the modified nanocarriers were compared and analyzed.The results showed that the targeting of the nano drug delivery systerms was greatly improved after modification with targeting peptides.Finally,pharmacodynamic study showed that L57&PGP-PEG-PAMAM loaded with Breviscapine could significantly improve the pathological characteristics of cerebral ischemia,reverse the necrosis and apoptosis of nerve cells,reduce the area of cerebral infarction by about 70%,reduce the neurological function score,inhibit the expression of inflammatory cytokines IL-15,IL-27,etc.Conclusion:L57&PGP-PEG-PAMAM nano carrier loaded with breviscapine can improve the experimental cerebral ischemia,and can accurately deliver drug molecules to the inflammatory site of cerebral ischemia. |
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