Preparation And Activity Evaluation In Vitro Of Camptothecin Powder Micronized By High-pressure Emulsification Method

CamPtothecin(CPT)is a natural antitumor alkaloid isolated from Chinese tree Camptotheca aeuminate,which has stronger antitumor activity for treating gastrointestinal cancer,bladder cancer,liver cancer,leukemia and malignant tumors.Right now,CPT is the only drug that can potent inhibitor of Topoisomerase I(Topo I)which was extracted from plant.Their antitumor mechanism is that CPT and its derivatives could stabilize the Topo I-DNA complex,formation of ternary complexes and subsequently influence the republication of DNA and cause the cell death.But due to its poor water soluble,generally in the form of sodium salt into injection preparation early clinical applications,and their ring opening form produce toxicity and antitumor activity is poor,always can not get a wide range of applications.In this research,we study a kind of high-pressure emulsification method to prepare CPT micronized powder.The micronized drug can increase the specific surface area,promote the dissolution of drugs,thus improving water soluble drug,further improve the bioavailability of drug.In the design of optimizing the high-pressure emulsification processes,particle size plays an important role in screening optimal conditions of nanoparticles preparation.This paper mainly studies the kind and dosage of surfactant,the concentration of drug in organic phase,the volume ratio of water and organic phase,homogenates time and homogenate speed,homogenization pressure and times.Characteristics of micronized CPT such as the drug encapsulation efficiency and drug loading efficiency were studied.In addition,the solid state,the local toxicity,cell uptake,and the inhibitory rate to liver cancer of nanoparticles were also discussed.The research results are as follows:1.Through a series of single factor experiments of high-pressure emulsification method to optimized the best process prepared of CPT nanoparticles,the best preparation conditions as follows:Tween-80 was chosen as the surfactant,the dosage was 0.4%;the concentration of CPT in chloroform and methanol(V;V=8:2)mixed solution was 1 mg/ml;the volume ratio of water and organic phase was 7:3;the homogenate speed was 7000 rpm for 11 min,the particle size of CPT mixed suspension was 30.3nm,the polydispersity was 0.356 under this condition.To further high-pressure homogeneous this suspension,and the homogeneous pressure was 200 bar,7 times.the particle size of CPT mixed suspension was 18.7nm,the polydispersity was 0.005 under this condition.2.Mannitol was chosen as lyoprotectant,joined the amount of five times for drug content.The particle size of CPT freeze-dried powder after dissolved with water was 165.6nm,polydispersity was 0.005,the particle dispersion uniform.3.To characterize the physico-chemical of mirconized CPT which got under the optimal conditions,including of SEM,FT-IR,MS,XRD,DSC and TG.The results showed that the main physicochemical properties has not changed during micronization.By the electronic scanning electron microscopy(SEM)images is visible after emulsification homogeneous CPT morphology changed significantly,an irregular flake,CPT reversed-phased size between 1-60μm,and after a homogeneous emulsion preparation of CPT producing,presents the rules of the strip shape,particle size in 1-4μm,the grain size is evener.Producing in good condition after dissolving,translucent and pan have milk state of light.FT-IR combined with MS results showed homogeneous emulsion prepared before and after the molecular structure of CPT did not change.XRD spectrum showed that API as the crystal shape,homogeneous of the CPT powder prepared by the emulsion crystallinity decreased significantly,the typical peak are reduced or absent,show that CPT after emulsification homogeneous prepared.4.We made in vitro release experiments of raw CPT and micronized CPT through simulating the human gastrointestinal tract in vivo environment.The results showed:the raw CPT powder due to poor water solubility,failed completely dissolved,the dissolution rate only 8.09%in 45min,meanwhile,the micronized CPT powder has dissolved 72.48%;the micronized CPT powder reached 93.22%in 240 min,and the raw powder was only 18.33%.The dissolution rate of micronized CPT powder was increased 5.09 times compared with the raw CPT powder.5.In the pharmacokinetic studies of rats,we used HPLC to detect Res content in rat plasma,and external standard one point method was used to calculate the CPT concentration of drug metabolism in rats.Results showed that compared with the raw CPT powder,the absorption and duration extensionof micronized CPT was increased in mice,relative bioavailability was increased 2.71 times.Through the above experimental results,we proved the prepared micronized CPT had uniform particle size distribution.The drug loading and encapsulation efficiency had achieved the desired results,their physical and chemical properties were stability,and had a certain degree of sustained-release function.Res original powder poorly soluble characteristics was significantly improved,thus improving its bioavailability.