Preparation And Pharmacokinetics Of Long-Circulating Gd-Dtpa Niosomes

Gd-DTPA was developed firstly as the water-soluble paramagnetic contrast agent for MRI, and had been widely used in clinical magnetic resonance imaging so far. It is a small molecule ionic contrast. After intravenous injection,it will rapidly diffuse to the extracellular space.And the half-life period is very short, therefore the enhancement effect of lesion sites (such as tumors) is not significant. Niosomes as drug carrier could take control of drug release, improve drug efficacy, target to special organizations or cells passively. Through modified by special molecules, drug could be delivered to specific organizations or cells. The thesis presented here focuses mainly on the preparation of the long-circulating niosomes encapsulating Gd-DTPA, its quality evaluation, the safety evaluation and the pharmacokinetic.1.In this part, HPLC determination was developed for Gd-DTPA and the encapsulation efficiency of the Long-circulating Gd-DTPA noisome. The dialysis method was used to divided the free Gd-DTPA from the niosomes and then methanol solution was applied to destroy the structure of niosomes. The calibration curve was liner in the range of 0.1-5mmol/L(R~2= 0.9997), The average recovery was in the range of 95%～105%. And it was proved a simple, rapid, and reproducible method. 2.The effect of different formulation factors on the encapsulation efficiency (EE) of niosomes was investigated, such as Span60/Brij700 molar ratio, Span60/CH molar ratio, Tween80 quantity, concentration, amount of water phase and hydration medium. The best prescription: Span60:CH(mol:mol)=2:1; water phase content is 10ml; drug concentration is 100mmol/L, Brij700 5% molar ratio, Tween80 less than 20%. A Reversed evaporation-freeze thawing method was used to prepare the Long-circulating Gd-DTPA niosomes. To increase the encapsulation efficiency of the noisome, several methods were compared, finally, the EE of water-soluble Gd-DTPA was improved to 50%.3.The characters were detected. Results show that the Long-circulating Gd-DTPA niosomes was transparents pherical liquid, and its average diameter is 48 nm, the Long-circulating Gd-DTPA niosomes appeared to be global vesicles,and the particle size of them was well distributed. The release of niosomes in vitro was well fitted with the Ritger-Peppas kinetics equation. The release of Gd-DTPA from Long-circulating Gd-DTPA niosomes was faster than Gd-DTPA niosomes ,while the release of Gd-DTPA slightly slower in the FBS/PBS medium than in the PBS.4.To Evaluate the safety of niosomes by Hemolysis test and cell toxicity experiment. Results show that the Brij700 and Tween80 as carrier do not have obvious hemolysis reaction. Cell toxicity properties show that the cytotoxicity of Gd-DTPA injection, blank Long-circulating niosomes and Long-circulating Gd-DTPA niosomes were all in grade 1 at 0.75μmol/ml, not obviously toxic. The cytotoxicity of blank Long-circulating niosomes was in grade 1at 0.75μmol/ml-2.5μmol/ml, which demonstrate that noisome as a drug delivery systern has good cytocompatibility.5. An ICP method was established to determine the concertration of Gd-DTPA in blood. After 3 administration of Gd-DTPA injection and niosomes to SD rat, pharmacokinetics parameters were calculated. in comparison with Gd-DTPA injection, the Long-circulating Gd-DTPA niosomes and the half-life period of Gd-DTPA niosomes were extended by 6.69and 2.57 times. AUC were increased by 2.43 and 1.59 times. So the Long-circulating Gd-DTPA niosomes have the ability to passively accumulate in tissues, and improve drug efficacy.