[Pharmacokinetics and distribution of superoxide dismutase liposomes in rats].

AIM: To evaluate the effects of surfactants on the pharmacokinetics and distribution in rats after intravenous administration of SOD liposomes. METHODS: The liposomes were prepared by reverse phase evaporation method. The activity of SOD was assayed by method of xanthine oxidase. RESULTS: The T1/2 of SOD solution, common SOD liposome, SOD liposomes modified by DSPE-PEG2000 and Tween 80 were 0.25, 0.34, 0.66 and 0.41 h, respectively; AUC were 12.48, 24.66, 41.16 and 33.02 microg x h x mL(-1), respectively. Compared with the common liposome, the liposomes modified by DSPE-PEG and Tween 80 decreased the content of SOD in liver and spleen, but increased in brain. CONCLUSION: The three kinds of liposomes could increase T1/2 and AUC in some extent, especially in PEG-L group. Tween-L could increase the SOD content in brain, and PEG-L could decrease the SOD content in the liver and spleen compared with the common liposome.

[Establishment of an in vitro model of brain-blood barrier].

OBJECTIVE: To establish an in vitro model of brain-blood barrier (BBB) using cultured mouse brain microvascular endothelial cells (BMVEC). METHODS: Mouse BMVEC were seeded on micro-pore membrane of gelatin-coated cell culture insert and cultured to confluence. The establishment of BBB was preliminary judged by a 4 h water-leaking test. The tight junctions between BMVEC were demonstrated by scanning and transmission electron microscope. The transendothelial electrical resistance(TEER) over BMVEC was measured. The permeability of Horseradish peroxidase (HRP) through the BBB was analyzed and the effect of RMP-7 on permeability of the BBB was investigated. RESULTS: The 4 h water-leaking test became positive when BMVEC were cultured to confluence. By scanning and transmission electron microscope, the tight junctions were demonstrated on confluent BMVEC. The TEER over BMVEC monolayer increased 3.2 and 7.68 times and the permeability rates for HRP were 13.4% and 6.7% respectively, as compared with sub-confluent BMVEC and human umbilical vein endothelial cell monolayer(HUVEC). The HRP permeability rate in the model of BBB increased 2.7 times after treatment with RMP-7. CONCLUSION: The established in vitro model of BBB has basic characteristics of BBB in vivo, and is suitable for central nervous system (CNS) drug research over BBB.

[Therapeutic efficiency of amphotericin B liposome modified by RMP-7 to transport drug across blood brain barrier].

AIM: To study the therapeutic efficiency of amphotericin B liposome (AmB-L) targeting to the brain in mice with meningitis. METHODS: Amphotericin B liposome targeting to the brain were prepared by film-sonication method. Their concentration and encapsulation percentage were determined. The Candida albicans was injected into the brain of BALB/c mice and the meningitis model was set up. Then the therapeutic efficiency of amphotericin B liposome targeting to the brain was studied. RESULTS: The encapsulation percentage of amphotericin B liposome was 93.3%. The meningitis model was set up after the Candida albicans was injected into the brain of BALB/c mice for 2 h. The therapeutic efficiency was increased after conjugating RMP-7 (the commercial nama is Cereport) to the surface of amphotericin B liposome. CONCLUSION: The therapeutic efficiency of Amphotericin B liposome targeting to the brain in the mice with meningitis was better than that of the common amphotericin B liposome and the life of the mice in AmB-L-PEG-RMP-7 group was longer than that of the mice in AmB-L-PEG group and AmB-L-PEG + RMP-7 group.

[Study on nerve growth factor liposomes on crossing blood-brain barrier in vitro and in vivo].

AIM: To study the permeability of nerve growth factor (NGF) liposomes (NGF-L, NGF-SSL, NGF-SSL-T) on the blood-brain barrier (BBB) model and the distribution in vivo, and analyze the correlation between the results in vitro and in vivo. METHODS: The BBB model in vitro was established by using mouse brain microvascullar endothelial cell, and the model was applied to study the permeability of NGF liposomes. The distribution of NGF of each group was studied by 125I labeled and SDS-PAGE method. RESULTS: The highest encapsulation proportion was 34%, and the mean size of NGF liposomes was below 100 nm. The permeability of NGF liposomes on in vitro BBB model showed that the liposome could promote NGF to transport across the BBB, the permeability of NGF-SSL-T was the highest. The distribution in the brain showed in an order of NGF concentration NGF-SSL-T > NGF-SSL + RMP-7 > NGF-SSL > NGF-L. There was a close relationship between P(e) (permeability coefficient on in vitro BBB model) and BUI (brain uptake constant in vivo). CONCLUSION: Liposomes can promote NGF to transport across the BBB, and the transporting ability BBB of NGF-SSL-T which RMP-7 incorporated into the surface of NGF liposomes is the best.

[Studies on the formation mechanism of alginate-chitosan microcapsule and its drug-loading and release properties on macromolecular drug].

AIM: To investigate the formation mechanism, macromolecular drug loading capacity and release property of alginate-chitosan microcapsules (ACM). METHODS: ACM was prepared by emulsification-gelation method and its formation mechanism was studied by DSC analysis. Using bovine serum albumin (BSA) as model drug, the drug loading and release properties of the microcapsules on macromolecular drug were investigated. RESULTS: The results of DSC analysis showed that there is electrostatic interaction between materials encapsulated in the microcapsule. With the increase of BSA microcapsule ratio, the BSA loading percentage rose from 9.20% to 35.08%; and with the ascent of chitosan (CTS) concentration, the BSA loading percentage increased from 30.29% to 38.12%. The BSA microcapsules whowed a two-phase release in both 0.1 mol.L-1 HCl and phosphate buffer saline (pH 7.4). With the increase of CTS concentration, the BSA release more and more slowly in 0.1 mol.L-1 HCl. CONCLUSION: Spheric and well-dispersed alginate-chitosan microcapsules were prepared. The microcapsule showed good loading capacity to BSA as well as sustained release to a certain degree.

[Effect of surfactants on the in vitro and in vivo properties of amphotericin B liposome].

AIM: Some surfactants such as DSPE-PEG, Tween 80 and Brij 35 were used to modify the amphotericin B liposome, improve the stability, optimize the tissue distribution and decrease the toxicity of amphotericin B liposome. METHODS: The amphotericin B liposome was prepared by the film-supersound method. The effects of cholesterol and amphotericin B on the encapsulation percentage were studied. The diameter, leakage percentage in phosphate buffer solution(PBS) and calf blood serum, and tissue distributions of amphotericin B liposome in the rat were determined. RESULTS: The top encapsulation percentage of amphotericin B liposome is (91.2 +/- 1.6)%. After modification with DSPE-PEG, Tween 80 and Brij 35, the encapsulation percentages were improved, the average diameters were decreased and the stabilities were improved, the amphotericin B concentrations in the liver, spleen and kidney were decreased, and the amphotericin B concentrations in the brain were increased, especially in the AmB-L-Tween 80 group. CONCLUSION: DSPE-PEG and Brij 35 could decrease the clearing of reticuroendothelial systems(RES) to the amphotericin B liposome and Tween 80 could facilitate the transporting of amphotericin B liposome into the brain.

[Preparation of thrombus-targeted urokinase liposomes and its thrombolytic effect in model rats].

AIM: To prepare thrombus-targeted urokinase liposomes and observe its improved thrombolytic efficacy on thrombus model rats. METHODS: The ligand H-Arg-Gly-Asp-Ser-OH (RGDS) which has specific affinity to thrombus was synthesized by liquid phase method and anchored on the surface of liposomes by incorporating its conjugate with DSPE-PEG3,500-COOH into liposomal lipid bilayers, thus thrombus-targeted liposomes were produced. Urokinase (UK) liposomes were prepared at room temperature through method modification using hydrogenated soy phosphatidylcholine (HSPC); the in vivo thrombolysis of the obtained thrombus-targeted UK liposomes and its comparison with TBS (Tris-HCl buffered solution) control, free UK and UK liposomes were assessed on common carotid artery model rats. RESULTS: The obtained liposomes were characteristic of high UK entrapment efficiency, small mean diameter and good storage stability. At the same dose (60,000 U.kg-1), compared to the wet thrombi weights of TBS control group, those of free UK group and UK liposome group showed no statistical difference, while those of targeted UK liposomes group were significantly decreased (P < 0.001); when evaluated in term of dry thrombi weights the result was slightly different. Compared to UK liposomes of the same dose, the targeted UK liposomes showed significantly improved thrombolytic efficacy (P < 0.01 in wet weights decrease and P < 0.05 in dry weights decrease respectively). CONCLUSION: The targeted UK liposomes displayed good targeted thrombolytic effect.

[Study on the hepatocytic cell targetability of liposomes].

AIM: To target for hepatocytic cell, liposomes was modified by special ligand. METHODS: Sterically stabilized liposomes (SSL) was conjugated with asialofeticin (AF), the ligand of asialoglycoprotein receptor (ASGP-R) of hepatocyte. ASGP-R-BLM is the ASGP-R reconstructed on bilayer lipid membrane (BLM). The recognition reaction between AF-SSL and ASGP-R-BLM can be monitored by the varieties of membrane electrical parameters. The targetability of AF-SSL mediated to hepatocyte was detected by radioisotopic labeled in vitro and in vivo. The therapeutic effect of antihepatocarcinoma was observed also. RESULTS: The lifetime of ASGP-R-BLM decreased with the added amount of AF-SSL. It was demonstrated that there was recognition reaction between AF-SSL and ASGP-R-BLM. The combination of AF-SSL with hepatocyte was significantly higher than that of SSL without AF-modified in vitro and in vivo. The survival time of rat for AF-SSL carriered ADM (adriamycin) group was much longer and the toxicities on heart, kidney and lung were lower than those SSL carried ADM group. CONCLUSION: It is possible to actively target the cell with specific receptor by ligand modified liposomes. The result prvide scientific basis of hepatocyte targeted liposomes.

[Effect of RMP-7 and its derivatives on the transportation of liposome into the brain].

AIM: To study the action of RMP-7 and its derivative on transporting liposome across the blood brain barrier (BBB) into the brain. METHODS: RMP-7 and DSPE-PEG-NHS [[1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-n-[poly (ethylene-glycol)]-hydroxy succinamide]] were conjugated together in mild condition and MALDI-TOF-MS (Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry) was used to determine their molecular ratio. An in vitro BBB model was established and used to determine in vitro bioactivity of RMP-7 and its derivative. The fluorescence of brain slices and the Evens Blue (EB) concentration in the brain, liver, spleen, lung and kidney of each group were used to evaluate the in vivo bioactivity of RMP-7 and its derivative on transporting liposome across the BBB. RESULTS: The average molecular weight (MW) of the reaction product was 4,900, while those of DSPE-PEG-NHS and RMP-7 were 3,224 and 1,098. The results demonstrated that RMP-7 was conjugated to DSPE-PEG-NHS at the molecular ratio of 1:1, so the product was DSPE-PEG-RMP-7. RMP-7 and DSPE-PEG-RMP-7 was shown to improve the transporting of peralcohol enzyme across the in vitro BBB model 2-3 times higher than the peralcohol enzyme only. DSPE-PEG-RMP-7 could facilitate the transporting of EB into brain more easily than RMP-7. CONCLUSION: Both RMP-7 and DSPE-PEG-RMP-7 could facilitate the transporting of liposome across the BBB, especially DSPE-PEG-RMP-7.

Studies on alginate-chitosan microcapsules and renal arterial embolization in rabbits.

Spherical and well-dispersed alginate-chitosan microcapsules, with a mean diameter of 77.28+/-0.93 microm (n=3), were prepared by the emulsification-gelation method. Adriamycin hydrochloride (ADM) was used as a model drug to investigate the drug loading capacity and release characteristics of the microcapsules. The drug/carrier ratio and chitosan concentration influenced the encapsulation efficiency of adriamycin. The adriamycin release from microcapsules was obviously different in 0.1 mol/l HCl from that in phosphate-buffered saline (PBS, pH 7.4). The drug was completely and rapidly released in 0.1 mol/l HCl, while it showed a sustained release after a burst release in PBS. The increase in chitosan concentration had no effect on adriamycin release in PBS. Using sulforhodamin B (SRB)-staining survival assay, the inhibition of adriamycin alginate-chitosan microcapsules (ADM-ACM) to different cancer cell lines (human BGC-823 cells, Bel-7402 cells and Hela cells) in vitro was determined. The inhibitory rate of ADM-ACM suspension to the three cell lines significantly outran that of ADM solution, no matter at high or low concentration. The effects of blank alginate-chitosan microcapsules (BACM) on renal arterial embolization were examined with transcatheter arterial embolization in rabbits. The angiogram and histopathological results indicated the blank microcapsules had excellent short- and long-term effects on renal arterial embolization.