Preparation And Preliminary Evaluation Of AML

Asparaginase(ASP)was the first therapeutic enzyme to be found with anti-tumor characteristics.In 1953,ASP was extracted from guinea pig serum for the first time.However,human serum lacks of ASP.Tumor cells rely on the protein synthesized by asparagine to maintain their malignant hyperplasia.ASP could quickly hydrolysis asparagine to aspartic acid and ammonia,as the result tumor cells blocked by protein synthesis and die.ASP is widely used in the treatment of lymphatic system malignancies,such as children acute lymphoblastic leukemia,Hodgkin lymphoma,lymphatic sarcoma and black sarcoma.Although the inhibiting effect of ASP on tumor cells is obvious,the disadvantages of short half-life,poor stability and high immunogenicity limit the application of ASP and other macromolecular drugs in clinical practice.We prepared asparaginase loaded in self-assembled molecular biomimetic lipidic nanocapsule(AML).The good biocompatibility of AML and good encapsulation and protective effect of self-assembled nanocapsules on ASP can improve the stability of protein drugs and bioavailability in vivo.In this study,AML was prepared for the first time.The physical and chemical properties,catalytic activity,stability and activity improvement mechanism and pharmacokinetics of AML were preliminarily studied.This study includes the following five parts.In the first part,AML was prepared by reverse evaporation method.And the appearance,particle size,zeta potential and conductivity of AML were investigated.Preparation of AML was opaque white uniform suspension liquid with opalescence.The appearance of AML was spherical by transmission electron microscope.And the average particle size,zeta potential and conductivity was 328.13 nm,13.13 mV and 1212.33 ?S/cm,respectively.In the second part,the optimal temperature and optimal pH of AML were investigated.Results showed that the optimum temperature of AML was 40 ?.And the optimum pH of AML was 7.5.In the third part,the stability of AML was tested.Results showed that the thermal stability,acid base stability,antitrypsin hydrolysis ability and metal ion stability of AML were all better than that of free ASP.In the fourth part,the mechanism of enhancement of AML activity and stability was investigated.The result showed: ASP and AML films interact with each other;after the interaction effect of AML membrane,the microenvironment around the active region of ASP could be changed;the protection of AML membrane can effectively prevent the structure change of ASP under the high temperature condition,thus maintaining the active form of ASP.In the fifth part,the pharmacokinetic characteristics of AML in rats were investigated.The result showed that AML could improve the pharmacokinetic properties of ASP,prolong the residence time of ASP in vivo,and improve the bioavailability of ASP.