| The amphiphilic copolymer of Poly (methoxy-polyethyleneglycol cyanoacrylate-co-n-hexadecyl cyanoacrylate) (PEG-PHDCA) was synthesized and used as surface modified material. Hydroxycamptothecin was used as a model drug and the stealth niosomes were prepared. The mechanism of niosome self-assembly and the interaction between HCPT and span were studied; the relation between physicochemical characteristics, in vitro biological parameters, in vivo Pharmacokinetics and biodistribution parameters were investigated; thus the stealth and tumor-targeting mechanism of niosomes were illustrated.The PEG-PHDCA was synthesized and characterized in terms of the critical association concentration (CAC) and hemolysis. The method of high performance liquid chromatography (HCPT) was set up to determine the concentration of 10-hydroxycamptothecin (HCPT). The apparent solubility of HCPT in distilled water and octanol was measured; the apparent partition coefficients of HCPT in octanol/distilled water determined. The pKa was calculated from the process of carboxylate form of HCPT into lactones form in diferent pH solutions.HCPT niosomes were prepared by film dispersion-hydration and sonication method. The single factor experiment and orthogonal design were adopted to obtain the optimized prescription. As a result, PEG5000-PHDCA niosomes of different particle size of around 80nm,150nm, 210nm, and PEG-PHDCA niosomes (around 80nm) of different PEG chain length (PEG Mr2000, 5000 and 10000)were prepared. PHDCA niosomes (around 80nm) was made as a control group. In order to improve the stability, HCPT niosomes were further lyophilized.The niosomes were characterized in terms of particle size, morphology, zeta potential, fixed aqueous layer thickness, PEG surface density and in vitro drug release. The result showed that all niosomes had a spherical shape. The particle surface was very smooth. With increasing PEG chain length, the zeta potential and fixed aqueous layer thickness of PEG-PHDCA niosomes dramatically increased while PEG incorporation rate as well as PEG surface density was lowered. The data had significant differences between three groups (p<0.05) . With the increase of particle size, PEG5000-PHDCA niosomes had an reduced zeta potential (p>0.05) , fixed aqueous layer thickness (p>0.05) and PEG surface density (p<0.05). More than 80%of drug was stabilized as lactone form when encapsulated in the niosomes. In vitro, the higher the chain length of PEG, the smaller the particle size was, the faster the drug was released. The drug release pattern was controlled by the diffusion mechanism.CPP value of Span was 0.5227, indicating that span could form niosomes. DSC and XRD experiment showed that HCPT was molecularly dispersed in the bilayer of niosomes and HCPT had a strong interaction with the bilayer. Hydrogen bond was found between span and HCPT, accountable for the increasing melting point of HCPT. The hydrophobic reaction as well as hydrogen bond strength was proved to be drug loading force.The niosomes were furtherly characterized in terms of complement consumption, protein adsorption and phagocytic uptake. In different PEG chain length of PEG-PHDCA niosomes, PEG5000-PHDCA niosomes was the best to avoid complement consumption, protein adsorption and phagocytic uptake. In different particle size groups of PEG5000-PHDCA, the small group of 80nm had the best inhibition rate.After IV administration of HCPT injection and niosomes to Wistar rat, pharmacokinetics parameters were calculated. It turned out that PEG5000-PHDCA niosomes with particle size from 80 ^ 150n 210nm could extend the half-life of HCPT by 15.88, 8.77 and 6.18 times(p<0.001), respectively, when AUC was enhanced by 24.50, 18.69, 7.17-fold. PEG-PHDCA niosomes (around 80nm) of different PEG chain length, namely PEG Mr of 2000, 5000, 10000, could prolonged the half-life of HCPT by 9.94, 15.88, 8.86-fold and AUC increased by 8.40, 24.50, 6.24-fold. There were also significances between PHDCA niosomes and PEG-PHDCA niosomes.The biodistribution test was carried out on S-180 tumor bearing Kuming mice. I2'I-HCPT was used as a radioactive probe. PHDCA niosomes were mainly captured by liver and spleen; AUC in tumor was similar with AUC in blood compartment. PEG-PHDCA niosomes showed a reduced uptake by liver and spleen, enhanced AUC in tumor compared with AUC in heart and blood compartment. In PEG-PHDCA niosomes with different PEG chain length, PEG5000-PHDCA showed a highest Cnlax and longest tmax as well as the least liver and spleen capture. In PEG5000-PHDCA niosomes with different particle sizes, the small group(80nm) has the best tumor targeting effects and liver/spleen evading effects.The mechanism of tumor-targeting effect of PEG-PHDCA niosomes was... |
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