In situ polycondensation of amino acid modified liposomes and their properties

Three amphiphilic amino acids based on glutamic acid, i.e. S-[1-carboxy-2-([N-bistetradecyl- -glutamate]carbon-yl)ethyl]cysteine (1), S-[1-carboxy-2-([N-bishexadecyl- -glutamate]carbonyl)ethyl]cysteine (2), S-[1-carboxy-2-([N-bis-octadecyl- -glutamate]carbonyl)ethyl]cysteine (3), were synthesized. The aggregation behavior of them in water or buffer solution was studied. It was found that upon hydration and sonication in water, they could form stable liposomes. This kind of amino acid modified liposome was then polycondensed locally on the liposome surface to form a polypeptide-surfaced liposome and the peptide formation was detected by Fr-IR, GPC, etc. The effect of polycondensation of amino acid on the properties of liposomes were studied by detecting the phase transition temperatures with DSC or measuring the leakage of the encapsulated fluorescent probe from the liposomes. It was observed that the phase transition temperatures of the peptide liposomes moved down and the polycondensation of amino acid moieties obviously increased the leakage of the encapsulated molecules.     

果酸脂质体的制备、检测及应用

以大豆卵磷脂为包封材料 ,用反相蒸发法制备果酸脂质体。并用透射电子显微镜表征了其形态结构 ,证实其直径在1 0 0纳米～ 2 0 0纳米之间。研究了果酸浓度对包封率 ,稳定剂浓度对脂质体稳定性的影响。结果表明 ,果酸浓度为 0 .3mg/ml时可以得到较好的包封率 ,丙二醇的适宜浓度是 5 % -1 5 % ,最终将脂质体应用于化妆品中 ,并证明是可行的     

狂犬病疫苗脂质体冻干粉的免疫原性评价

目的评价狂犬病疫苗脂质体冻干粉的免疫原性。方法将狂犬病疫苗原液稀释至15 IU/mL,制备为稀释液冻干粉(Y1组);将该稀释液冻干粉与脂质体冻干粉按5∶3的体积比混合,制成物理混合物(Y2组);同时采用冻融-冻干法将狂犬病疫苗稀释液和脂质体配制成狂犬病疫苗脂质体冻干粉(Y3组)。将各组疫苗复溶后,分别于0、3、7、14、21 d经小鼠腹腔给药,0. 5 mL/只。MTT法检测小鼠脾淋巴细胞增殖能力,流式细胞术检测T淋巴细胞表面标记,ELISA法测定小鼠体液中狂犬病病毒抗体IgG(RV-IgG)浓度。结果与Y1组及Y2组比较,Y3组初次免疫后3 d小鼠脾细胞刺激指数(stimulatingindex,SI)值明显升高(P <0. 01);初次免疫后7、14、21、28 d,CD4^+/CD8^+值明显升高(P <0. 05),初次免疫后7、14、21 d,RV-IgG浓度明显升高(P <0. 05)。结论狂犬病疫苗脂质体冻干粉在小鼠体内具有良好的免疫原性,脂质体能提高疫苗免疫原性,延长疫苗的免疫时间,有望开发成为新一代广泛应用的疫苗佐剂。     

响应面法优化西兰花种子萝卜硫素前体脂质体的制备工艺

将萝卜硫素制成前体脂质体以提高萝卜硫素的稳定性,改善其水溶性和生物利用度.以包封率和粒径为指标,分别考察了载体材料、表面活性剂种类和用量及脂药比的影响,响应面法优化得前体脂质体的最优处方.通过常温稳定性实验考察了脂质体和前体脂质体的稳定性.结果表明,最优处方为脂药比为6.5∶1,NaCl与萝卜硫素质量比为105∶1,泊...     

新型脂质体吸附乙肝疫苗的稳定性及其抗病毒作用

目的 研究新型脂质体及其与乙肝疫苗结合物的稳定性以及结合物抗病毒作用。方法 通过外观观察、粒径检测及诱导BALB/c小鼠产生特异性抗体IgG1和IgG2a的水平考察稳定性;免疫HBV转基因小鼠,检测其血清中HBsAg和抗-HBs的滴度。结果 4℃存放1年,脂质体有少量沉淀产生,粒径变大;而脂质体与乙肝疫苗结合物全部沉淀,粒径变大,但均易摇匀,无结块;结合物4℃存放1年,诱导BALB/c小鼠产生特异性抗体IgG1和IgG2a的水平没有下降;HBV转基因小鼠于免疫后2、3、4个月,体内的HBsAg的A值较免疫前有显著下降。抗-HBs在初次免疫2个月后的阳转率为100％。结论 脂质体吸附乙肝疫苗稳定性好,且有一定的抗病毒作用。     

Intelligent release of cinnamon oil from engineered proteoliposome via stimulation of Bacillus cereus protease

Inspired by the hydrolysis of casein by protease, a new approach to deliver antimicrobials against bacterial infections was developed in this study. As a natural antibacterial agent, cinnamon oil was encapsulated into engineered liposomes inlaid with casein. The average particle size of proteoliposomes was 615.0 nm and their entrapment efficiency (EE) was 40.0%. In this work, Bacillus cereus (B. cereus) was chosen as model bacterium. The controlled release of liposome-encapsulated cinnamon oil was realized via bacterial protease secreted from B. cereus. As a result, 99.99% of the bacteria could be efficiently inhibited in rice and wheat flour.     

Yellow discoloration of the liposome system of cuttlefish (Sepia pharaonis) as influenced by lipid oxidation

Lipid oxidation, discoloration, loss of amine groups and pyrrolization of the liposome systems of cuttlefish (Sepia pharaonis) in the presence of FeCl₃ and ascorbic acid were studied. Thiobarbituric acid-reactive substances (TBARS) and the b^∗-value of cuttlefish liposomes increased with a coincidental decrease in amine groups when the incubation temperatures (0, 4, 25, and 37 °C) and incubation times (0–24 h) were increased (p < 0.05). As lipid oxidation and yellow pigment formation in the cuttlefish liposome proceeded, a loss of amine groups and pyrrolization were also detected. The effects of FeCl₃ and ascorbic acid, at different concentrations, on TBARS production, b^∗-value, loss of amine groups and pyrrolization of cuttlefish liposome were also investigated. Both FeCl₃ and ascorbic acid showed prooxidative effects in cuttlefish liposome in a concentration-dependent manner. Sodium chloride (0–2%) reduced TBARS, b^∗-values and pyrrole compounds. These results suggest a positive correlation between lipid oxidation and the development of yellow pigments in cuttlefish phospholipids.     

Synergism and antagonism between quercetin and other chain-breaking antioxidants in lipid systems of increasing structural organisation

Antioxidative effect of quercetin was affected differently in neat sunflower oil, in methyl linoleate o/w emulsion and in phospholipid liposomes by the other chain-breaking antioxidants, α-tocopherol, rutin and astaxanthin. Quercetin was better than or comparable to α-tocopherol as an antioxidant in the three lipid systems. The presence of α-tocopherol showed a strong synergistic effect for quercetin in the emulsion, less in the liposomes and a clear antagonistic effect in the neat oil. Astaxanthin, without any effect alone in neat oil or in the liposomes, but with some effect in the emulsion, did not affect quercetin as an antioxidant. Rutin was only effective as an antioxidant in the liposomes where rutin showed clear synergism with quercetin. The interaction of quercetin with the other antioxidants is classified according to the structural organisation of the lipid substrate.     

Aquifex aeolicus membrane hydrogenase for hydrogen biooxidation: Role of lipids and physiological partners in enzyme stability and activity

Hydrogenase I from the hyperthermophilic bacterium Aquifex aeolicus is a good candidate for biotechnological devices thanks to its ability to oxidize hydrogen at high temperature, even in the presence of oxygen and CO. In order to enhance the enzyme stability and the catalytic efficiency, we investigated the hydrogen oxidation process with hydrogenase I embedded in a physiological-like environment. Hydrogenase I partners in the metabolic chain, namely membrane quinone and cytochrome b, were purified and fully characterized. The complex hydrogenase I–cytochrome b was inserted into liposomes. Surface Plasmon Resonance revealed that quinone took part in the stabilization of the complex. By use of molecular modelization and electrochemistry analysis, enzyme stability has been demonstrated to be stronger and enzymatic efficiency to be five times higher when hydrogenase is embedded into the liposomes. This result raises the possibility of using hydrogenases as biocatalysts in fuel cells.     

Effect of nanovesicle-encapsulated nisin on growth of Listeria monocytogenes in milk

Commercial nisin was encapsulated in nanovesicles (mean diameter 140 nm) prepared from partially purified soy lecithin. Nisin-loaded liposomes and unencapsulated (free) nisin were initially tested in BHI medium and skim milk inoculated with Listeria monocytogenes and incubated for 48 h at 30 °C. At such abuse temperature conditions, free nisin showed better inhibitory than the liposomal counterparts. Subsequently, the effect of encapsulated or free nisin was evaluated in combination with refrigeration (7 ± 1 °C) in both whole (3.25% fat) and skim (0% fat) milk for up to 14 day. A decrease of 3–4 log cycles in L. monocytogenes counts was observed for free and encapsulated nisin at 0.5 mg/ml concentration. Liposome encapsulation of antimicrobial peptides may be important to overcome stability issues and interaction with food components. The utilization of nanovesicle-encapsulated nisin in combination with low temperatures appeared to be effective to control L. monocytogenes in milk, emphasizing the importance of hurdle technology to assure food safety.