Preparation And Preliminary Study Of The L-Asparaginase Loaded In Hydroxyproply-?-Cyclodextrin Liposomes

L-asparaginase(ASP)as a therapeutic enzyme,has been extensively used in clinics for many years as a first-line therapeutic agent for acute lymphoblastic leukemias and lymphomas.ASP is able to catalyze the deamination of L-asparagine.The normal cells can synthesis L-asparagine while cancer cells can't,so lack or reduction of L-asparagine will induce death or growth inhibition of cancer cells.Being a therapeutic enzyme and essentially a protein drug,ASP had intrinsic drawbacks such as low catalytic activity under physiological situation,low stability and short circulating life.Hydroxypropyl-?-cyclodextrin liposomes might be novel promising nanovesicles for effective systemic delivery of therapeutic enzyme ASP.And it might increase the enzymatic activity,improved the stabilities and favorably changed the in vivo kinetic characteristics.In the experiments below,L-asparaginase loaded in hydroxypropyl-?-cyclodextrin liposomes(AHLP)was prepared to deliver the therapeutic enzymes ASP efficiently for the first time.Its physicochemical properties,optimum temperature,optimum pH,and enzymatic stabilities,pharmacokinetics were investigated.In Chapter ?,the physicochemical properties of AHLP were investigated.AHLP was prepared reverse evaporation method.The average particle size of AHLP was 389 nm.Its average zeta potential was-9 mV.And the average entrapment efficiency of AHLP was 56%.In Chapter ?,the optimum temperature and optimum pH of AHLP was investigated.The optimum temperature of the AHLP was 40?.And the optimum pH of AHLP was 7.5.AHLP could improve the activity of ASP.In chapter ?,the temperature stability,acid-base stability,proteolytic stability,plasma stability of AHLP in vitro were investigated.AHLP could improve the stabilities of ASP.In chapter ?,the related mechanisms of AHLP were investigated.The altered fluorescence intensities suggested that after entrapment,not only the microenvironment changes but also the interactions between hydroxypropyl-?-cyclodextrin liposomes membranes and ASP molecules might occur.The entrapment of ASP in AHLP might retard the conformational changes of ASP.These changes could improve the activity and stabilities of ASP in AHLP.In Chapter ?,the pharmacokinetic properties of AHLP in rats after intravenous injection were investigated.AHLP favorably modified the in vivo pharmacokinetic behaviors of ASP.Compared with ASP,AHLP could not only remain active for longer but also improve bioavailability.