Bioavailability of griseofulvin in the form of liposomes]

Liposomes containing griseofulvin have been prepared by shaking method. Lecithin and cholesterol were used to compose phospholipid bilayer of liposomes. The suspension of liposomes in 0.9% sodium chloride and the suspension of griseofulvin in 0.25% iostonic methylcellulose solution were used in the comparative study in vivo. Both suspensions were administered intragastricly to rats. Parameters of bioavailability have been found on the basis of the changes in griseofulvin plasma concentrations versus time. Intragastric administration of griseofulvin in liposomes suspension demonstrates ca. 40% higher Cmax and AUC when compared to these of griseofulvin suspension which indicates a better bioavailability.     

Radiopaque liposomes: effect of formulation conditions on encapsulation efficiency

Liposomes containing sodium ioxitalamate were prepared by sonication. Suitable amounts of purified soybean phosphatidylcholine and cholesterol were used at various molar ratios. Stearylamine or dicetylphosphate were added to this lipid composition when charged liposomes were required. After sonication and removal of unencapsulated solute, this manufacturing process yielded small multilamellar vesicles as confirmed by electron microscopy. These liposomes did not exhibit a narrow range of size distribution; the mean particle size varied from 135 to 145 nm. With respect to the efficiency of encapsulation, two parameters were distinguishable: the volume of encapsulated aqueous space per unit of lipid weight and the percentage of the contrast agent added that became encapsulated in the liposomes. Investigation of the preparative parameters revealed that increased molar ratios of cholesterol yielded higher aqueous volume and iodine contents in the liposomes, which were attributed to a reduction of the liposome permeability to the contrast agent. However, the inclusion of cholesterol into the bilayer liposomal membrane was limited, probably by solubility restrictions. Negatively and positively charged liposomes had higher rates of encapsulation than did neutral liposomes. This result was expected since efficient encapsulation of polar compounds requires formation of large aqueous spaces within the vesicles per mole of lipids. Increase of the lipid fractions at a constant, reduced the aqueous volume entrapped per millimole of lipid and, consequently, the iodine content in the liposomes. However, an increase in the initial sodium ioxitalamate concentration diminished the aqueous volume entrapped in the liposomes but increased the iodine content.     

Evaluation of hybrid liposomes-encapsulated silymarin regarding physical stability and in vivo performance

Silymarin, a known standardized extract obtained from seeds of Silybum marianum is used in treatment of liver diseases of varying origins. Aiming at improving its poor bioavailability from oral products, silymarin hybrid liposomes are introduced in this work for buccal administration after investigating their stability and in vivo hepatoprotective efficiency. Silymarin loaded hybrid liposomes composed of lecithin (L), cholesterol (Ch), stearyl amine (SA) and Tween 20 (T20) in molar ratio of (9:1:1:0.5) were prepared. Their stability upon storage was studied at 4 degrees C and at ambient conditions. Stored samples were analyzed for percent encapsulation, drug release, particle size, turbidity measurement and visual changes. Characterization of the blend between phospholipid and silymarin was done using FT-IR and DSC which indicated a possible interaction. The stabilized formula of silymarin hybrid liposomes was evaluated upon buccal administration regarding its hepatoprotective activity against carbon tetrachloride-induced oxidative stress in albino rats. The degree of protection was measured using biochemical parameters like serum glutamic oxalacetate transaminase (SGOT) and serum glutamic pyruvate transaminase (SGPT). The introduced silymarin hybrid liposomes produced a significant decrease in both transaminase levels when challenged with CCl(4) (intraperitonially) in comparison with orally administered silymarin suspension. This improvement was also confirmed histopathologically.     

Effervescent granule based proliposomes of ibuprofen

Proliposomes of ibuprofen were successfully prepared using effervescent granules as solid carriers of dried phospholipids along with other lipids (soyabean lecithin, stearylamine and cholesterol). Liposomes of regular size with uniform size distribution resulted when proliposomal formulations were hydrated under the effervescence produced by the production of carbon dioxide gas. The inert atmosphere of carbon dioxide gas prevents the chance of oxidative degradation of phospholipids. The size distribution of liposomes was noted to be related to the degree of agitation provided by effervescence. Encapsulation efficiency of liposomes derived from proliposomes was shown to be nearly 100 per cent. Preparations were shown to be quite stable at 20 degrees C when stored under an umbrella of nitrogen. The enhanced anti-inflammatory activity of ibuprofen entrapped in liposomes was exhibited when compared with plain ibuprofen following intravenous administration using the carrageenan induced paw oedema test.     

The effect of ileal brake activators on the oral bioavailability of atenolol in man

The aims of this study were to develop novel liposome formulations for tranexamic acid (TA) from various lipid compositions [neutral (hydrogenated soya phosphatidylcholine and cholesterol), positive (stearylamine) or negative (dicetyl phosphate) charged lipid], and to investigate the effects of concentrations of TA (5 and 10% in DI water) and charges on the physicochemical properties of liposomes. Liposomes were prepared by chloroform film method with sonication. The physical (appearance, pH, size, morphology) and chemical (drug encapsulation efficiency, transition temperature, enthalpy of transition) properties of liposomes were characterized. The TA contents were determined spectrophotometrically at 415 nm, following derivatization with 2,4,6-trinitrobenzosulfonic acid. The charged liposomes demonstrated better physical stability than the neutral liposomes. The percentages of TA entrapped in all liposome formulations varied between 13.2 and 15.6%, and were independent of TA concentrations and charges of liposomes. Charges affected the physical stability, pH and size of liposomes. The particle sizes of negative blank and positive liposomes (with and without the entrapped drug) were approximately 10 times larger than the negative liposome with the entrapped TA. The multilamellar 7:2:1 molar ratio of hydrogenated soy phosphatidylcholine/cholesterol/dicetyl phosphate entrapped with 10% TA liposome (10%TA,-) was selected for further release study, due to its high physical stability, small particle size and relatively high drug encapsulation efficiency.     

Increasing bioavailability of silymarin using a buccal liposomal delivery system: preparation and experimental design investigation

Silymarin is a natural lipotropic agent of low bioavailability from oral products. The aim of our study is to prepare buccal liposomal delivery system of silymarin with higher bioavailability. The effect of lecithin:cholesterol molar ratio on the percentage drug encapsulated was investigated. The influence of fluctuating the amount of added drug was also determined. The effect of additives such as positive charge inducer, negative charge inducer and surfactants was studied using two different 2(3) full factorial designs. Furthermore, additives used to optimize liposomal product were also investigated for their optimal concentrations, release properties and in vitro permeation and absorption through chicken cheek pouch. Optimal liposomal encapsulation efficiency was found at 7:4 lecithin to cholesterol molar ratio. A decrease in entrapment efficiency with increasing cholesterol content was observed. Tween 20 or Tween 80 beyond 0.5 molar ratio decreased the entrapment efficiency. Positively charged liposomes showed superior entrapment efficiency over neutral and negatively charged liposomes. Release studies as well as permeation and absorption studies showed that hybrid liposomes prepared according to formula 3 containing lecithin, cholesterol, stearyl amine and Tween 20 in 9:1:1:0.5 molar ratio, respectively, gave the best drug absorption and permeation. It showed steady state permeation through chicken cheek pouch for 6h. This is expected to improve the bioavailability of silymarin in the developed liposomal buccal delivery system, as the results show an increase in drug penetration compared to free drug powder.     

Leakage of sulphobromophthalein from large simple bilayer phospholipid vesicles

Single bilayer phospholipid vesicles containing entrapped sulphobromophthalein were prepared from a phospholipid film in the presence of deoxicholate at a molar ratio of deoxicholate to phospholipid of 1:2. The trapping efficiency of these vesicles was a function of sulphobromophthalein concentration during incubation, reaching a maximum at a molar ratio of egg lecithin to sulphobromophthalein of 25:1. Release of sulphobromophthalein from liposomes was observed when the vesicles were incubated with bovine serum albumin. The sulphobromophthalein released appeared to be associated with albumin when analysed by Sepharose 4B gel filtration. Leakage of sulphobromophthalein from liposomes was also observed when the vesicles were incubated with different amounts of oleic acid. However, the amount of sulphobromophthalein released from liposomes was much lower than that observed in the presence of bovine serum albumin. These vesicles incorporated up to one molecule of oleic acid for each two and a half molecules of egg lecithin, and appear to be suitable as acceptors in studies of fatty acid transfer between membranes.     

Characteristics and anti-proliferative activity of azelaic acid and its derivatives entrapped in bilayer vesicles in cancer cell lines

The hydrophilicity and lipophilicity of azelaic acid (AA) were modified to diethyl azelate (DA) which was synthesized by Fisher esterification reaction and identified by IR, MS and (1)H NMR and to azelaic acid-beta-cyclodextrin complex (AACD) which was prepared by inclusion complexation and identified by IR, DSC and XRD respectively. AA, DA and AACD were entrapped in liposomes and niosomes comprising of L-alpha-dipalmitoyl phosphatidylcholine (DPPC)/cholesterol at 7:3 molar ratio and Tween61/cholesterol at 1:1 molar ratio, respectively, using a thin-film hydration method with sonication. The size and morphology of these bilayer vesicles were determined by optical and transmission electron microscopy. The particle size was found to be in the range of 90-190 nm. The entrapment efficiency of AA, DA and AACD in all vesicular formulations was more than 80%, as analyzed by HPLC for AA and AACD, and GC for DA. Anti-proliferative activity of AA and its derivatives (DA and AACD) both entrapped and not entrapped in bilayer vesicles, using MTT assay in three cancer cell lines (HeLa, KB and B(16)F(10)) comparing with vincristine, were investigated. AACD showed the highest potency comparing to AA in HeLa, KB and B(16)F(10) of 1.48, 1.6 and 1.5 times, respectively. AA entrapped in liposomes was about 90 times more potent than the free AA, and about 1.5 times less potent than vincristine. When entrapped in bilayer vesicles, DA and AACD were more effective than AA in killing cancer cells. AACD entrapped in liposomes gave the highest anti-proliferation activity in HeLa cell lines with the IC(50) of 2.3 and 327 times more potent than vincristine and AA, respectively. DA in liposomes demonstrated the IC(50) of 0.03 times less potent than vincristine in KB cell lines, while in B(16)F(10) AACD in niosomes showed the IC(50) of 0.05 times less potent than vincristine. This study has suggested that the modification of AA by derivatization and complexation as well as the entrapment in bilayer vesicles can enhance its therapeutic efficacy.     

Leakage of sulphobromophthalein from large simple bilayer phospholipid vesicles

Abstract

Single bilayer phospholipid vesicles containing entrapped sulphobromophthalein were prepared from a phospholipid film in the presence of deoxicholate at a molar ratio of deoxicholate to phospholipid of 1 :2. The trapping efficiency of these vesicles was a function of sulphobromophthalein concentration during incubation, reaching a maximum at a molar ratio of egg lecithin to sulphobromophthalein of 25 :1. Release of sulphobromophthalein from liposomes was observed when the vesicles were incubated with bovine serum albumin. The sulphobromophthalein released appeared to be associated with albumin when analysed by Sepharose 4B gel filtration. Leakage of sulphobromophthalein from liposomes was also observed when the vesicles were incubated with different amounts of oleic acid. However, the amount of sulphobromophthalein released from liposomes was much lower than that observed in the presence of bovine serum albumin. These vesicles incorporated up to one molecule of oleic acid for each two and a half molecules of egg lecithin, and appear to be suitable as acceptors in studies of fatty acid transfer between membranes.     

Subcutaneous administration of sterically stabilized (stealth) liposomes is an effective sustained release system for 1-β-d-arabinofuranosylcytosine

We have previously demonstrated that 1-β-D-arabinofuranosylcytosine (ara-C) entrapped in long-circulating formulations of liposomes (Stealth, or sterically stabilized) was an effective sustained release system following intravenous (iv) or intraperitoneal (ip) administration (Cancer Res. 52, 2431-2439). We have recently shown that, following subcutaneous (sc) administration, Stealth liposomes can achieve substantial levels in the circulation. The therapeutic effect of sc-administered liposomal ara-C against murine L1210 leukemia was examined as a function of route of injection, liposome size, and liposome composition. When the liposomes contained polyethylene glycol-distearoylphosphatidylethanolamine (PEG-DSPE) and cholesterol, sc injection was as effective in increasing lifespan as iv injection against iv or ip tumor. This effect was independent of liposome size or fluidity of the phospholipid. Liposomes lacking PEG-DSPE or lacking cholesterol were significantly less efficacious. Long-term survivors could be obtained following three weekly sc injections of PEG-liposomes.     

去氢骆驼蓬碱脂质体制备工艺优化及抗肝癌活性

目的 制备去氢骆驼蓬碱脂质体并对其制备工艺进行优化，评价脂质体的相关表征及对肝癌细胞的毒性。方法 用薄膜水化法制备去氢骆驼蓬碱脂质体。以包封率作为评价指标，以大豆卵磷脂和药物的质量比、大豆卵磷脂与胆固醇的质量比和超声时间作为评价因素对脂质体包封率的影响。并对脂质体的粒径、Zeta电位、外观和稳定性进行评价。CCK-8法对比去氢骆驼蓬碱和去氢骆驼蓬碱脂质体的抗肝癌细胞增殖活性。结果 最优制备工艺：大豆卵磷脂和药物的质量比为11.4：1，大豆卵磷脂与胆固醇的质量比为4.4：1，超声时间为33 min。在此条件下制备的脂质体的包封率为81.88%，粒径为143.65 nm，Zeta电位为-12.68 mV，低温环境稳定性良好，具有缓释效应。去氢骆驼蓬碱脂质体的抗肝癌细胞增殖活性大于裸药。结论 所制得的去氢骆驼蓬碱脂质体包封率和稳定性均符合标准。将去氢骆驼蓬碱制备成为脂质体能提高其抗肝癌细胞增殖活性。     

Hypoglycemic effect of liposome-entrapped insulin administered by various routes into normal rats

We entrapped insulin into liposomes using one combination of lipids comprising egg lecithin-cholesterol-stearylamine (7:2:1 molar ratio). The efficiency of entrapment was about 20% with unsonicated liposomes (LMV), and around 5% with sonicated liposomes (SUV). LMV-, SUV- and free-insulins were administered via different routes into male, non-diabetic Wistar rats in order to change the glycemia. When administered parenterally all preparations acted in a similar manner, reducing the glycemia after 2 h in the range of 75% to 85% in case of iv administration, and 43% to 67%--after sc administration. Only liposome insulin acted via intragastric route, and SUV-insulin-via buccal--or nasal route.     

High efficiency entrapment of superoxide dismutase into mucoadhesive chitosan-coated liposomes

Superoxide dismutase (SOD), antioxidative enzyme and potential anti-inflammatory agent, was encapsulated into mucoadhesive chitosan-coated liposomes in order to increase its releasing time and to facilitate its cellular penetration. Positively, neutrally and negatively charged liposomes were prepared using soybean lecithin, stearylamine, phosphatidyl glycerol and cholesterol. The effects of liposomal lipid composition and protein to lipid ratio on the encapsulation parameters were studied in three preparation methods: dehydration–rehydration, hydration and proliposome methods. The highest efficiency of SOD entrapment, 39–65%, was achieved by the proliposome method. Vesicles prepared by the hydration method entrapped 1–13% and vesicles prepared by dehydration–rehydration entrapped 2–3% of SOD. Stability tests for SOD-loaded liposomes prepared by the proliposome method showed no significant loss of the enzyme activity within 1 month at 4 °C or within 2 days at 37 °C. Positively, neutrally and negatively charged liposomes, prepared by the proliposome method, were successfully coated with two types of low and medium molecular weight chitosans. Both types of chitosan coating increased the mucoadhesive characteristics of all three types of vesicles. Using the proliposome method and subsequent chitosan coating, highly efficient SOD-loaded vesicles for drug targeting on mucosal tissues could be produced.     

Distribution of liposomal breviscapine in brain following intravenous injection in rats

AIM: To investigate distribution of breviscapine in brain after intravenous (i.v.) injection of liposomes. METHODS: Breviscapine liposomes were prepared by rotary evaporation-sonication method. Particle size, encapsulation efficiency and stability of liposomes were respectively examined. In vitro drug release was investigated in 0.9% sodium chloride at 37 degrees C. Rats were divided into two groups. Liposomes were given to one group and commercial injection (Injectio Breviscapine) was given to the other at a single dose of 28.1 mgkg(-1) i.v., respectively. Scutellarin in rat brain at different sampling time was determined by RP-HPLC. The brain concentration-time curves of breviscapine liposomes and commercial injection were constructed and pharmacokinetic parameters were calculated and compared by statistic analysis. RESULTS: The average liposome diameter was 735+/-59 nm and encapsulation efficiency was 85.1+/-2.3%. The average accumulative release percentage of breviscapine liposomes in 0.9% sodium chloride was less than 30% within 24h. The mean concentration-time curves of breviscapine liposomes and commercial injection were both fitted to one-compartment model. There are significant difference of parameter T(1/2) and AUC(0-360) between liposome and commercial injection (p<0.05). T(1/2) of breviscapine liposomes and commercial injection were 23.13+/-7.71 and 6.27+/-1.84min, respectively. The brain AUC ratio of breviscapine liposomes to commercial injection was 443.4+/-92.3%. CONCLUSION: Compared with the commercial injection, liposomes delivered more drugs into the brain and have longer elimination time.     

小鼠口服多糖包覆胰岛素脂质体的降血糖作用小鼠口服多糖包覆胰岛素脂质体的降血糖作用

目的 研究壳聚糖和海藻酸钠两种多糖包覆胰岛素脂质体的小鼠po降血糖作用。方法 用逆相蒸发法制备胰岛素脂质体;用透射电镜和激光粒度仪测定它们的形态和粒径;用HPLC法和超速离心法测定包封率;用胃蛋白酶和胰蛋白酶溶液试验多糖包覆脂质体对胰岛素的保护作用;用酶-苯酚法测定小鼠po多糖包覆胰岛素脂质体后降血糖作用。结果小鼠po 0.1%壳聚糖和0.1%海藻酸钠包覆的胰岛素脂质体具有较好的降血糖作用。结论壳聚糖或海藻酸钠包覆的脂质体能减少胃蛋白酶或胰蛋白酶对胰岛素的降解并促进胰岛素po吸收。     

氨甲喋呤(MTX)脂质体的制备及其稳定性

本文探讨了提高MTX脂质体包裹率、影响它对热稳定性的因素,并自行设计了简便、迅速、重现性好的测定MTX脂质体的方法。结果表明:采用二次乳化蒸发法制备MTX脂质体,在控制乳化温度及有机相比例的条件下,可获得50%左右较高的包裹率。另外提示,脂质体分散溶媒的离子强度和脂质体中胆固醇的含量是影响MTX脂质体对热稳定性的重要因素。以选用50mM的磷酸盐缓冲液为分散溶媒和PC/CHOL/SA的脂质体组成,则100℃加热30分钟灭菌,所包MTX可滞留90%。且灭菌前后的脂质体经电镜观察形态无明显变化。     

Intraliposomal chemical activation patterns of liposomal cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexane platinum (II) (L-NDDP)-a potential antitumour agent

L-NDDP is a liposome-entrapped platinum compound currently in phase 2 clinical trials that has been shown to undergo intraliposomal activation. The degradation/activation kinetics of liposome entrapped cis-bis-neodecanoato-trans-R,R-1,2-diamminocyclohexane platinum (II) [L-NDDP] at different conditions of pH, and temperature is presented. Liposomes were reconstituted in a solution of 0.9% sodium chloride (NaCl) in water (pH 5) at room temperature (formulation conditions currently used in the ongoing clinical trials). In the temperature experiments, L-NDDP 0.9% sodium chloride liposomes were incubated in a water-bath at 40, 60, and 80 degrees C. In the pH experiments, these solutions were compared to water, phosphate with and without chloride ion present, phosphate buffer without chloride ion at pH 3.1, 5.0, and 7.4, and glycine buffer with and without chloride ion. In 0.9% sodium chloride at room temperature, the chemical degradation/activation of liposome-bound NDDP was biphasic, with most of the degradation (approximately 45% conversion) occurring during the first hour after formation of the liposome suspension. NDDP degradation was pH dependent: when using pH 3 phosphate buffer as a reconstituting solution, liposome-bound NDDP degraded rapidly, whereas in pH 7.4 phosphate buffer it was stable for > 72 h. NDDP degradation was also temperature-dependent, the 50% point decreasing from 12 h at 25 degrees C to 9.5 h at 40 degrees C, 3.8 h at 60 degrees C, and 0.3 h at 80 degrees C when using 0.9% NaCl in water as a reconstituting solution. Using glycine buffer solution with and without NaCl at room temperature, no NDDP degradation over a 72 h period was observed at 25 degrees C; however, at 40 degrees C, only 68% NDDP remained intact at 72 h. Atomic absorption spectrophotometry (AAS) analysis of the eluting fractions after injection of L-NDDP samples reconstituted in chloride-containing and non chloride-containing solutions clearly indicated that the formation of DACH-Pt-Cl2 was only observed when chloride-containing solutions were used and was first detected at 3 h when using 0.9% NaCl in water as a reconstituting solution. These results indicate that pH and temperature, and not the presence of chloride ion, are the main factors leading to the activation of NDDP. Since 45% of NDDP is already degraded at 1 h in the same conditions, it is concluded that (1) the first active intermediates of L-NDDP formed within the liposomes are the DACH-Pt chloro-aquo and diaquo intermediates, and (2) the in vivo, antitumour activity of L-NDDP is most likely mediated by direct intracellular delivery of the active species.     

Liposomal gel with chloramphenicol: characterisation and in vitro release

The aim of our study was to develop a liposomal carrier system for the local treatment of bacterial vaginosis, capable to efficiently deliver entrapped drug during an extended period of time. Chloramphenicol was entrapped in liposomes composed of egg phosphatidylcholine/egg phosphatidylgycerol-sodium (9:1, molar ratio) and prepared by two different methods, the proliposome method and the polyol dilution method. Both liposome preparations were characterised and compared for particle size, polydispersity, entrapment efficiency and tested for in vitro stability in media that simulate human vaginal conditions (buffer pH 4.5 and vaginal fluid simulant). To achieve application viscosity of liposomes and to further improve their stability, liposomes prepared by the proliposome method were incorporated in the bioadhesive gel made of Carbopol 974P NF resin. In vitro release studies of liposomes incorporated in the gel have shown a prolonged release of entrapped chloramphenicol compared to control gel. Even after 24 hours of incubation in the vaginal fluid simulant, more than 40% of the originally entrapped drug was still retained in the gel. Storage stability studies have proven the ability of the Carbopol 974P NF gel to preserve the original size distribution of incorporated liposomes. All the performed experiments confirm the applicability of liposomes as a novel drug carrier system for the local treatment of bacterial vaginosis.     

Intraliposomal chemical activation patterns of liposomal cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexane platinum (II) (L-NDDP)-a potential antitumour agent

L-NDDP is a liposome-entrapped platinum compound currently in phase 2 clinical trials that has been shown to undergo intraliposomal activation. The degradation/activation kinetics of liposome entrapped cis-bis-neodecanoatotrans-R,R-1,2-diamminocyclohexane platinum (II) [L-NDDP] at different conditions of pH, and temperature is presented. Liposomes were reconstituted in a solution of 0.9% sodium chloride (NaCl) in water (pH 5) at room temperature (formulation conditions currently used in the ongoing clinical trials). In the temperature experiments, L-NDDP 0.9% sodium chloride liposomes were incubated in a water-bath at 40, 60, and 80 C. In the pH experiments, these solutions were compared to water, phosphate with and without chloride ion present, phosphate buffer without chloride ion at pH 3.1, 5.0, and 7.4, and glycine buffer with and without chloride ion. In 0.9% sodium chloride at room temperature, the chemical degradation/activation of liposome-bound NDDP was biphasic, with most of the degradation (approximately 45% conversion) occurring during the first hour after formation of the liposome suspension. NDDP degradation was pH dependent: when using pH 3 phosphate buffer as a reconstituting solution, liposome-bound NDDP degraded rapidly, whereas in pH 7.4 phosphate buffer it was stable for &gt; 72h. NDDP degradation was also temperature-dependent, the 50% point decreasing from 12h at 25C to 9.5h at 40C, 3.8h at 60C and 0.3h at 80C when using 0.9% NaCl in water as a reconstituting solution. Using glycine buffer solution with and without NaCl at room temperature, no L-NDDP degradation over a 72h period was observed at 25C; however, at 40C, only 68% NDDP remained intact at 72h. Atomic absorption spectrophotometry (AAS) analysis of the eluting fractions after injection of L-NDDP samples reconstituted in chloridecontaining and non chloride-containing solutions clearly indicated that the formation of DACH-Pt-Cl₂ was only observed when chloride-containing solutions were used and was first detected at 3h when using 0.9% NaCl in water as a reconstituting solution. These results indicate that pH and temperature, and not the presence of chloride ion, are the main factors leading to the activation of NDDP. Since 45%of NDDP is already degraded at 1h in the same conditions, it is concluded that (1) the first active intermediates of L-NDDP formed within the liposomes are the DACH-Pt chloro-aquo and diaquo intermediates, and (2) the in vivo, antitumour activity of L-NDDP is most likely mediated by direct intracellular delivery of the active species.     

Characteristics and anti-proliferative activity of azelaic acid and its derivatives entrapped in bilayer vesicles in cancer cell lines

The hydrophilicity and lipophilicity of azelaic acid (AA) were modified to diethyl azelate (DA) which was synthesized by Fisher esterification reaction and identified by IR, MS and ¹H NMR and to azelaic acid-β-cyclodextrin complex (AACD) which was prepared by inclusion complexation and identified by IR, DSC and XRD respectively. AA, DA and AACD were entrapped in liposomes and niosomes comprising of l-α-dipalmitoyl phosphatidylcholine (DPPC)/cholesterol at 7:3 molar ratio and Tween61/cholesterol at 1:1 molar ratio, respectively, using a thin-film hydration method with sonication. The size and morphology of these bilayer vesicles were determined by optical and transmission electron microscopy. The particle size was found to be in the range of 90–190 nm. The entrapment efficiency of AA, DA and AACD in all vesicular formulations was more than 80%, as analyzed by HPLC for AA and AACD, and GC for DA. Anti-proliferative activity of AA and its derivatives (DA and AACD) both entrapped and not entrapped in bilayer vesicles, using MTT assay in three cancer cell lines (HeLa, KB and B₁₆F₁₀) comparing with vincristine, were investigated. AACD showed the highest potency comparing to AA in HeLa, KB and B₁₆F₁₀ of 1.48, 1.6 and 1.5 times, respectively. AA entrapped in liposomes was about 90 times more potent than the free AA, and about 1.5 times less potent than vincristine. When entrapped in bilayer vesicles, DA and AACD were more effective than AA in killing cancer cells. AACD entrapped in liposomes gave the highest anti-proliferation activity in HeLa cell lines with the IC₅₀ of 2.3 and 327 times more potent than vincristine and AA, respectively. DA in liposomes demonstrated the IC₅₀ of 0.03 times less potent than vincristine in KB cell lines, while in B₁₆F₁₀ AACD in niosomes showed the IC₅₀ of 0.05 times less potent than vincristine. This study has suggested that the modification of AA by derivatization and complexation as well as the entrapment in bilayer vesicles can enhance its therapeutic efficacy.