Studies On Preparation And Character Of Nanoparticles As Anti-cancer Drug Delivery Systems

Biodegradable polymeric nanoparticles as drug delivery systems have been investigated in this dissertation. The preparation and character of nanoparticles, the in vitro drug release, cytostatic activity and in vivo pharmacokinetics of drug-loaded nanoparticles were studied. The research was mainly concerned with the following aspects. 1. Doxorubicin-loaded chitosan nanoparticles(1) The chitosan nanoparticles were prepared by the ion cross-linked method. The optimum conditions for preparing smaller nanoparticles were determined. At the optimum conditions, the nanoparticles obtained had the smallest size. The mean diameter of nanoparticles was 183nm with a narrow distribution. From the observation of transmission electron microscopy(TEM), the nanoparticles exhibited a spherical shape. IR spectra of nanoparticles showed that there was linkage between phosphoric group of TPP and ammonium ion of chitosan, which was the reason of the formation of nanoparticles.(2) The encapsulation efficiency of doxorubicin was enhanced greatly by the formation of doxorubicin-TPP complex firstly. In the preparation of doxorubicin-loaded nanoparticles, doxorubicin was formed doxorubicin-TPP complex firstly, and then loaded into nanoparticles. The optimum conditions to prepare doxorubicin-loaded nanoparticles with high encapsulation efficiency were determined. The encapsulation efficiency of doxorubicin was 82.75%, and drug loading was 17.2%. The nanoparticles were round in shape with mean diameter of 193nm. The zeta potential of nanoparticles was +52.1mv. The nanoparticles were stable and had no change in size during a long period.(3) The in vitro release of doxorubicin-loaded chitosan nanoparticles demonstrated that the release behavior of doxorubicin exhibited a triphasic pattern characterized by a fast initial release, followed by a constant release and then a slower and continuous release. The nanoparticles had rather good doxorubicin sustained release. The Higuchi equation could well described the in vitro release curve of nanoparticles. The release speed of doxorubicin from nanoparticles was influnced by theamount of doxorubicin, the deacetylation degree and molecular weight of chitosan.(4) The cytostatic activity of doxorubicin-loaded chitosan nanoparticles was analyzed by the MTT method. Compared with the control doxorubicin injection, the doxorubicin-loaded chitosan nanoparticles could not only maintain the bioactivity of doxorubicin but also enhance its bioavailability.2. Paclitaxel-loaded polylactide(PLA) and poly(DL-lactide-co-glycolide) (PLGA) nanoparticles(1) A binary solvent dispersion method has been investigated in the preparation of nanoparticles of PLA and PLGA. The effects of ethanol on the nanoparticle size and yield have been examined by using of cloud point titration method. It was found that the yield of nanoparticles increased with increase of ethanol in mixture with acetone and attained a maximum value near the cloud point, whereas the size of nanoparticles decreased with increase of ethanol in the solution with acetone and attained a minimum value near the cloud point.The optimum conditions for preparing polymeric nanoparticles were determined. The yield of nanoparticles was above 90% with the average size being ranged in 130~180nm for both PLA and PLGA.At the critical flocculation point(CFPT) of PLA and PLGA nanoparticles, the concentration of electrolyte Na2SO4 was above 0.7mol/L, which was much higher than the concentration of electrolyte in blood. It proved that nanoparticles could be stable at the concentration of electrolyte in blood. The results of enzyme degradation of the polymeric nanoparticles showed that the speed of degradation increased with the increase of glycolide part in polymer and the increase of enzyme concentration. The enzyme degradation happened both on the surface of nanoparticles and inner them, which was a process of homogenous degradation.(2) The optimum conditions for preparing paclitaxel-loaded nanoparticles were also determined. At the optimum conditions, the encapsulation efficiency of paclitaxel-loaded nanoparticles with higher drug loading was up to 90%.The size of paclitaxel-loaded nanoparticles was similar to that ofdrug-free nanoparticles, whose mean size ranged from 130nm to 180nm. The differential scanning calorimetry(DSC) analysis of paclitaxel-loaded nanoparticles showed that paclitaxel was in an amorphous phase of a molecular dispersion in the nanoparticles. The nanoparticles were stable and had no change in size and distribution during a long period.Since the existence of carboxylic groups, the zeta potential of both drug-loaded nanoparticles and drug-free nanoparticles were negative. After modified by DSPE-PEG, the surface charge of nanoparticles decreased since the long chain of PEG masked the negative charge present in the nanoparticles. In addition, the size of nanoparticles had a trend of increase.(3) The in vitro release of paclitaxel-loaded nanoparticles demonstrated that nanoparticles had rather good sustained release. The Higuchi equation could well described the in vitro release curve of nanoparticles. Paclitaxel-loaded nanoparticles prepared with different polymer or different concentration of surfactant could continuously release paclitaxel at different speed.(4) The cytostatic activity of paclitaxel-loaded nanoparticles was analyzed by the MTT method. Compared with the control paclitaxel injection, the paclitaxel-loaded nanoparticles could not only maintain the bioactivity of paclitaxel but also enhance its bioavailability. In addition, it is helpful to the use of paclitaxel in clinic by its incorporation into nanoparticles, which avoids the use of Cremophor EL with side effect.(5) Pharmacokinetics was evaluated in mice after invo injection of paclitaxel, which was formulated in Cremophor EL or in drug-loaded nanoparticles. At the same content of paclitaxel, long-circulating nanoparticles could stay in the blood circulation for a longer time, with Ti/2fj6.38h, against Ti/2p2.11h of conventional nanoparticles and T]/2p 0.7lh of paclitaxel injection. Since the modification of DSPE-PEG, long-circulating nanoparticles could greatly increase the circulation time of paclitaxel in blood stream.