| N-acetylcysteine(NAC)is a precursor of intracellular reduced glutathione with versatile functions covering anti-peroxidation,liver protection,immune regulation and inflammation inhibition.It is widely used in clinic and can be applied to the treatment of respiratory,liver,cardiovascular and cerebrovascular diseases,such as chronic obstructive pulmonary disease,severe liver disease,atherosclerosis and parkinson's disease.However,NAC is chemically unstable and exhibites a tendency of aggregation as a result of its sulfhydryl group.Considering the afore-mentioned defects of NAC,our group synthesized the acetylcysteine derivative XXH-32 earlier,a much stable form displays obvious anti-acute liver injury effects in vitro and in vivo.Yet,the efficacy of XXH-32 is limitted to its poor water-solubility,undesirable oral absorption and low bioavailability.Composed of phospholipids and cholesterol,liposome encapsulates drug in its biofilms-like lipid bilayers and consequently,protects the encapsulated drug,reduces drug toxicity and improve drug stability.Furthermore,liposome has good cell affinity,histocompatibility,sustained release and targeting properties.In order to improve the water-solubility and bioavailability of XXH-32,our research group loaded it into liposome and carried out related evaluation studies in vitro and in vivo,aiming to gain a sustained-release therapeutic effect on acute liver injury.The main research work includes:1.Pre-prescription study of XXH-32 liposome was carried out with in vitro analytical methods established,methodology certification carried on,equilibrium solubility and oil/water partition coefflent inspected.2.Study on the optimization of prescription and preparation of XXH-32 liposome:(1)The encapsulation efficiency of XXH-32 liposome was determined by low speed centrifugation.(2)The preparation method of XXH-32 liposomes was investigated by single factor experiment with encapsulation efficiency as index.The liposomes were prepared by thin-film dispersion method.The major influencing factors include the mass ratio of drug to lipid,cholesterol to phospholipid and the volume of hydration,which were later optimized by orthogonal design with entrapment efficiency,particle size and potential taken as criterions.The optimum preparation of liposome with 3mg XXH-32:the mass ratio of XXH-32 to lecithin is 1:40 with that of cholesterol to lecithin being 1:6,chloroform to water phase pH 6.60 phosphate buffer solution volume ratio is 1:2 with 10mL chloroform as organic phase,film forming temperature is 40 ? with hydration temperature being 37 ?,and 25%(total power 650 W)probe ultrasonic 8 minutes.3.Study on the quality of XXH-32 liposomes:(1)Under the optimal preparation process,the liposomes were presented round in shape with average diameter of(175.2±2.6)nm,PDI was 0.262±0.010.The content of XXH-32 in the liposome was(2.60± 0.12)%,and the entrapment efficiency was(95.05±1.06)%.(2)In vitro release of XXH-32 liposomes.Compared with free XXH-32,the liposomes presented a First-order kinetic behavior:the dissolution rate of XXH-32 liposomes exceeded 80.50%in 8 hours,while that of XXH-32 liposomes was only about 17.31%.The results indicated that XXH-32 liposomes had a significant sustained-release effect and the loaded drug was released through the lipid layer diffusion.4.Study on the pharmacokinetics and tissue distribution of XXH-32 liposome in mice:The pharmacokinetic properties of XXH-32 and XXH-32 liposome were investigated in male CD1 mice.The results showed that the relative uptake rate(Re)of XXH-32 liposomes in the liver was 2.74,suggesting that XXH-32 liposomes had better liver targeting.XXH-32 liposome will not accumulate in plasma,kidney,lung,heart and spleen for its Re is less than 1;The selectivity of liposomes to organs was liver>kidney>lung>heart>spleen,while XXH-32 was not selective to liver,and the two preparations exhibited significant differences in liver targeting. |
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