Liposomes as carriers for verbascoside: stability and skin permeation studies

In this study the influence of liposomal incorporation on both the stability and the in vitro (trans) dermal delivery of verbascoside was evaluated. The effect of drug entrapment into vesicles on its radical scavenging activity was also studied. Liposomes were obtained from soy phosphatidylcholine and cholesterol according to the film hydration method. Stability of verbascoside-loaded vesicles was studied over 6 months. Results showed that verbascoside can be incorporated in liposomes (E% = 57-66%), preventing its degradation. Stability studies (dynamic lager light scattering [DLLS] measurements and transmission electron microscopy [TEM] visualization) pointed out that vesicles were stable for 90 days and neither verbascoside leakage nor vesicle size alteration occurred during this period. The effects of vesicular incorporation on verbascoside diffusion through skin were investigated in vitro using newborn pig skin. Results showed that liposomes promoted drug accumulation into the stratum corneum but they did not give rise to any significant transdermal verbascoside delivery. Finally, results obtained from a 1, 1-diphenyl-2-pierylhydrazyl (DPPH) radical assay demonstrated that liposomes did not interfere with the radical scavenging activity of verbascoside.     

Liposomal formulations of protein proteinase inhibitors: Preparation and specific activity

Possibility of encapsulation of water-soluble proteins into multilayer liposomes of soybean zwitterionic phospholipid mixtures (phosphatidylcholine (PC) and phosphatidylethanolamine (PE)) was investigated. The influence of the PC/PE ratio (w/w) on efficiency of incorporation of the Bowman-Birk soybean proteinase inhibitor (BBI) and aprotinin (BPTI) into liposomes was studied. Protein encapsulation did not affect liposome sizes. Confocal laser scanning microscopy demonstrated that proteins were located in the central part of the spherical particle and also between bilayers. The study of biological (antitrypsin and antichymotrypsin) activity demonstrated partial spatial shielding of active sites of proteins entrapped in liposomes. The effect of an ionic detergent on the activity of the encapsulated BBI and BPTI is consistent with this hypothesis and suggests that this shielding is reversible. Stability of liposomes was examined using three various media modeling gastrointestinal fluids (gastric and intestinal juices and fluids). Data obtained indicate that the prepared liposomes seem to be promising formulations for BBI and BPTI delivery.     

DIMENSIONAL ANALYSIS AND SCALE-UP IN THEORY AND INDUSTRIAL APPLICATION*

A comparative study between archaeosomes, lipid lamellar vesicles made from archaea polar lipids, and conventional phospholipids liposomes was carried out, aiming at evaluating the properties and the potential of archaeosomes as novel colloidal carriers for effective drug delivery to the skin. Betamethasone dipropionate (BMD)–loaded archaeosomes and conventional liposomes were prepared by the thin-lipid film and sonication procedures, using, respectively, archaeal lipids extracted from archaea Halobacterium salinarum and enriched soy phosphatidylcholine. Vesicular formulations were characterized by assessing vesicle size, zeta potential, incorporation efficiency, and morphology. In order to investigate the effect of the incorporation in the two different colloidal carrier systems on the (trans)dermal delivery of BMD, in vitro drug permeation studies through full-thickness pig skin were carried out by using Franz diffusion vertical cells by testing both archaeal and liposomal dispersions. Interestingly, archaeosomes appeared to be the most effective carriers for the model drug, achieveing a major drug penetration and accumulation in the skin strata, especially in the epidermis. This can, presumably, be due to the enhanced archaeosomal bilayer fluidity, as indicated by the rheological studies that provided insight into the viscoelastic properties of all the studied systems. The available data suggest that suitably developed archaeosomes may hold great promise as delivery vehicles for topical applications.     

pH-sensitive non-phospholipid vesicle and macrophage-like cells: binding, uptake and endocytotic pathway

Phospholipid and non-phospholipid vesicles are extensively studied as drug delivery systems to modify pharmacokinetics of drugs and to improve their action in target cells. It is believed that the major barrier to efficient drug delivery is entrapment of drugs in the endosomal compartment, since this eventually leads to its degradation in lysosomes. For these reasons, the knowledge of internalization pathway plays a fundamental role in optimizing drug targeting. The aim of this work is to characterize pH-sensitive Tween 20 vesicles, their interaction with macrophage-like cells and their comparison with pH-sensitive liposomes. The effect of different amounts of cholesteryl hemissucinate on surfactant vesicle formation and pH-sensitivity was studied. To evaluate the initial mode of internalization in Raw 264.7 and the intracellular fate of neutral and pH-sensitive formulations, flow cytometry in presence and in absence of selected inhibitors and fluorescence microscopy in absence and presence of specific fluorescent endocytotic markers were used. The obtained results showed that the surfactant vesicle pH-sensitivity was about two or three fold higher than that obtained with pH-sensitive liposomes in the presence of serum in vitro. The uptake mechanism of surfactant vesicles, after incubation with macrophage-like cells, is comparable to that of liposomes (clathrin-mediated endocytosis).     

Interactions of polymerizable phosphatidylcholine vesicles with blood components: relevance to biocompatibility

We have studied the biocompatibility properties of polymerizable phosphatidylcholine bilayer membranes, in the form of liposomes, with a view toward the eventual utilization of such polymerized lipid assemblies in drug carrier systems or as surface coatings for biomaterials. The SH-based polymerizable lipid 1,2-bis[1,2-(lipoyl)dodecanoyl]-sn-glycero-3-phosphocholine (dilipoyl lipid, DLL) and the methacryl-based lipid 1,2-bis[(methacryloyloxy)dodecanoyl]-sn-glycero-3-phosphocholine (dipolymerizable lipid, DPL) were studied in comparison to ‘conventional’ zwitterionic or charged phospholipids. We examined binding of serum proteins to liposomes and effects of liposomes on fibrin clot formation and on platelet aggregation. All types of liposomes tested bound complex mixtures of serum proteins with IgG being the most abundant bound component. DPL vesicles and anionic vesicles bound substantially more protein than other vesicle types. Polymerized DPL vesicles uniquely bound a protein of about 53 kDa which was not bound to other types of phosphatidylcholine liposomes. Likewise polymerized DPL vesicles, but not other types of phosphatidylcholine vesicles, caused a marked alteration in coagulation as measured by activated partial thromboplastin time (APTT) and prothrombin time (PT) tests; this effect was shown to be due to binding and depletion of clothing factor V by the DPL polymerized vesicles. Polymerized DPL liposomes and DLL liposomes in polymerized or nonpolymerized form, were without substantial effect on platelet aggregation. However, DPL nonpolymerized vesicles, while not causing aggregation, did impair ADP-induced aggregation of platelets. These studies suggest that SH based polymerizable lipids of the DLL type may be very suitable for in vivo use in the contexts of drug delivery systems or biomaterials development. Methacryloyl-based lipids of the DPL type seem to display interactions with the hemostatic process which militate against their in vivo utilization.     

Enhanced transdermal delivery of salbutamol sulfate via ethosomes

The main objective of the present work was to compare the transdermal delivery of salbutamol sulfate (SS), a hydrophilic drug used as a bronchodilator, from ethosomes and classic liposomes containing different cholesterol and dicetylphosphate concentrations. All the systems were characterized for shape, particle size, and entrapment efficiency percentage, by image analysis optical microscopy or transmission electron microscopy, laser diffraction, and ultracentrifugation, respectively. In vitro drug permeation via a synthetic semipermeable membrane or skin from newborn mice was studied in Franz diffusion cells. The selected systems were incorporated into Pluronic F 127 gels and evaluated for both drug permeation and mice skin deposition. In all systems, the presence of spherical-shaped vesicles was predominant. The vesicle size was significantly decreased (P < .05) by decreasing cholesterol concentration and increasing dicetylphosphate and ethanol concentrations. The entrapment efficiency percentage was significantly increased (P < .05) by increasing cholesterol, dicetylphosphate, and ethanol concentrations. In vitro permeation studies of the prepared gels containing the selected vesicles showed that ethosomal systems were much more efficient at delivering SS into mice skin (in terms of quantity and depth) than were liposomes or aqueous or hydroalcoholic solutions.     

Sustained release of acyclovir from nano-liposomes and nano-niosomes: an in vitro study

The present study was designed to develop and compare acyclovir containing nano-vesicular liposomes and niosomes based on cholesterol, soya L-alpha-lecithin and nonionic surfactant, span 20. The effort was made to study in vitro whether acyclovir-loaded nanovesicles could sustain the release of the drug by increasing residence time and thus, acyclovir could reduce its dose-related systemic toxicity. There were good vesicular distributions in both of the niosomes and the liposomes. The obtained vesicles were within 1 microm and about 35% of them were within a size of 100 nm. The percentage of drug loading varied and the niosomal vesicles contained more drug as compared with the liposomes. When the in vitro drug release was compared, it was found that the liposomes released about 90% drug in 150 min whereas the drug release was just 50% from the niosomal vesicles in 200 min. Again, the niosomes showed better stability compared with the liposomes. Thus, niosome could be a better choice for intravenous delivery of acyclovir.     

Propylene Glycol Liposomes as a Topical Delivery System for Miconazole Nitrate: Comparison with Conventional Liposomes

Propylene glycol (PG)-phospholipid vesicles have been advocated as flexible lipid vesicles for enhanced skin delivery of drugs. To further characterize the performance of these vesicles and to address some relevant pharmaceutical issues, miconazole nitrate(MN)-loaded PG nanoliposomes were prepared and characterized for vesicle size, entrapment efficiency, in vitro release, and vesicle stability. An issue of pharmaceutical importance is the time-dependent, dilution-driven diffusion of propylene glycol out of the vesicles. This was addressed by assessing propylene glycol using gas chromatography in the separated vesicles and monitoring its buildup in the medium after repeated dispersion of separated vesicles in fresh medium. Further, the antifungal activity of liposomal formulations under study was assessed using Candida albicans, and their in vitro skin permeation and retention were studied using human skin. At all instances, blank and drug-loaded conventional liposomes were included for comparison. The results provided evidence of controlled MN delivery, constant percent PG uptake in the vesicles (≈45.5%) in the PG concentration range 2.5 to 10%, improved vesicle stability, and enhanced skin deposition of MN with minimum skin permeation. These are key issues for different formulation and performance aspects of propylene glycol-phospholipid vesicles.     

风干羊肉中乳酸菌的体内外抗氧化特性

【背景】机体的衰老和一些疾病多与氧化作用有关,随着对抗氧化制剂研究的深入,人工合成抗氧化剂的安全性受到质疑,因此寻找天然抗氧化制剂的研究已成为热点。【目的】从风干羊肉中筛选抗氧化活性较高的乳酸菌,分析肉源乳酸菌体内外抗氧化能力。【方法】以24株肉源乳酸菌为研究对象,以自由基清除能力、亚铁离子螯合能力、还原能力及抗脂质过氧化能力为体外抗氧化能力分析指标,筛选出体外抗氧化活性较强的乳酸菌,运用16S rRNA基因序列同源性分析进行菌种鉴定,通过小鼠试验研究其体内抗氧化能力。【结果】试验所测24株乳酸菌均具有一定的体外抗氧化能力,其中菌株TR13为24株乳酸菌中体外抗氧化能力较强的菌株,其超氧阴离子自由基(·O2-)清除率为54.29%,羟自由基(·OH)清除率为90.84%, 1,1-二苯基-2-三硝基苯肼自由基(1,1-diphenyl-2-picrylhydrazyl,DPPH)清除率为99.38%,亚铁离子螯合率为55.85%,还原能力达1.345,抗脂质过氧化率为39.99%。通过16S rRNA基因鉴定,菌株TR13为一株瑞士乳杆菌。通过给D-半乳糖诱导的衰老型小鼠饲喂TR13菌...     

Effects of verbascoside,a phenylpropanoid glycoside from lemon verbena,on phospholipid model membranes

Phenylpropanoid glycosides are water-soluble compounds widely distributed, most of them deriving from medicinal herbs. Among them, verbascoside or acteoside has exhibited a wide biological activity, being free radical scavenging the most representative one. Moreover, antitumor, antimicrobial, anti-inflammatory, anti-thrombotic and wound healing properties have been previously described. Herein, the interaction of verbascoside with phospholipid membranes has been studied by means of differential scanning calorimetry, fluorescence anisotropy and dynamic light scattering. Verbascoside showed stronger affinity for negatively charged membranes composed of phosphatidylglycerol (PG) than for phosphatidylcholine (PC) membranes. This compound promoted phase separation of lipid domains in PC membranes and formed a stable lipid complex with and approximate phospholipid/verbascoside ratio of 4:1. Despite its hydrophilic character, verbascoside's caffeoyl moiety was located deep into the hydrophobic core of PC membranes and was almost inaccessible to spin probes located at different depths in PG membranes. This compound affected the ionization behavior of the PG phosphate group and most likely interacted with the vesicles surface. The presence of verbascoside decreased the particle size in PG unilamellar vesicles through the increase of the phospholipid head group area. A localization of verbascoside filling the upper region of PG bilayers close to the phospholipid/water interface is proposed. These effects on membranes may help to understand the mechanism of the biological activity of verbascoside and other similar phenylpropanoid glycosides.     

Fusogenic activity of PEGylated pH-sensitive liposomes

The aim of this study was to investigate the fusogenic properties of poly(ethylene glycol) (PEG)ylated dioleoylphosphatidylethanolamine/cholesteryl hemisuccinate (DOPE/CHEMS) liposomes. These pH-sensitive liposomes were prepared by incorporating two different PEG lipids: distearoylphosphatidylethanolamine (DSPE)-PEG???? was mixed with the liposomal lipids using the conventional method, whereas sterol-PEG???? was inserted into the outer monolayer of preformed vesicles. Both types of PEGylated liposomes were characterized and compared for their entrapment efficiency, zeta potential and size, and were tested in vitro for pH sensitivity by means of proton-induced leakage and membrane fusion activity. To mimic the routes of intracellular delivery, fusion between pH-sensitive liposomes and liposomes designed to simulate the endosomal membrane was studied. Our investigations confirmed that DOPE/CHEMS liposomes were capable of rapidly releasing calcein and of fusing upon acidification. However, after incorporation of DSPE-PEG???? or sterol-PEG???? into the membrane, pH sensitivity was significantly reduced; as the mol ratio of PEG-lipid was increased, the ability to fuse was decreased. Comparison between two different PEGylated pH-sensitive liposomes showed that only vesicles containing 0.6 mol% sterol-PEG???? in the outer monolayer were still capable of fusing with the endosome-like liposomes and showing leakage of calcein at pH 5.5.     

Fluidity enhancement: a critical factor for performance of liposomal transdermal drug delivery system

Liposomes are well known lipid carriers for drug delivery of bioactive molecules encapsulated inside their membrane. Liposomes as skin drug delivery systems were initially promoted primarily for localized effects with minimal systemic delivery. Subsequently, a novel vesicular system, transferosomes was reported for transdermal delivery with efficiency similar to subcutaneous injection. The multiple bilayered organizations of lipids applied in these vesicles structure are somewhat similar to complex nature of stratum corneal intercellular lipids domains. The incorporation of novel agents into these lipid vesicles results in the loss of entrapped markers but it is similar to fluidization of stratum corneum lipids on treatment with a penetration enhancer. This approach generated the utility of penetration enhancers/fluidizing agents in lipids vesicular systems for skin delivery. For the transdermal and topical applications of liposomes, fluidity of bilayer lipid membrane is rate limiting which governs the permeation. This article critically reviews the relevance of using different types of vesicles as a model for skin in permeation enhancement studies. This study has also been designed to encompass all enhancement measurements and analytical tools for characterization of permeability in liposomal vesicular system.     

Permeability studies on liposomes formed from polymerizable diacetylenic phospholipids and their potential applications as drug delivery systems

We have investigated the permeability and entrapment characteristics of liposomes formed from a group of polymerizable phospholipids, containing diacetylenic groups in one or both of their acyl chains. Permeability was assessed by the release of an entrapped dye, 6-carboxyfluorescein. Diacetylenic phosphatidylcholine (PC) liposomes were found to exhibit a wide range of permeability properties, depending on: the nature of the diacetylenic lipid, i.e. mixed-chain (mc) or identical-chain (id), the extent of polymerisation, vesicle size, and cholesterol content. Ultraviolet-initiated polymerisation affected a significant decrease in the permeability of C25idPC liposomes. The increase in permeability of liposomes formed from four other diacetylenic lipids (C25mcPC, C23idPC, C23mcPC and C20idPC) after polymerisation was attributed to disturbances in the packing of lipid molecules, and/or the limited ability of small unilamellar vesicles to accommodate long polymers. The C20idPC lipid is atypical, forming irregular monomeric and polymeric vesicles. The permeability of C25idPC liposomes was also assessed by the release of [3H]inulin. C25idPC liposomes exhibited low permeabilities to [3H]inulin in their monomeric and polymeric states. Incubation of C25idPC liposomes in human plasma caused a substantial increase in the permeability of monomeric vesicles to both carboxyfluorescein and [3H]inulin. The permeability of polymerised C25idPC liposomes, however, was unaffected in the presence of plasma, with vesicles retaining most of their entrapped [3H]inulin after 50 h. These findings demonstrate that polymeric C25idPC liposomes exhibit high resistance to the destructive actions of plasma components, such as high-density lipoproteins (HDLs). Polymeric C25idPC liposomes may have an application in drug delivery systems.     

Distribution of [3H]cholesterol-labelled liposomes with or without praziquantel in mice infected with Mesocestoides corti (Cestoda) tetrathyridia

The anthelmintic drug praziquantel (PZQ) has a short half-life in the circulation, necessitating repeated daily administration of PZQ for the therapy of larval stages of cestodes. The effect of incorporation of PZQ into multilamellar liposomes on their biodistribution in Mesocestoides corti (syn. M. vogae) infected mice has been examined using [3H]cholesterol as a liposomal marker. Incorporation of PZQ significantly increased the average size of liposomes with 70.3% of [3H]lip.PZQ particles up to 1.9 microm, whereas higher portion of [3H]liposomes (66.3% of total) were of smaller (up to 1.3 microm). Both liposome preparations were given intraperitoneally to avoid rapid sequestration in the liver. There were significant differences between [3H]liposomes and [3H]lip.PZQ-associated radioactivity in peritoneal adherent cells, liver- and peritoneal larvae, liver, spleen and lymph nodes within 16 days of examination. The highest uptake (about 2-fold more [3H]lip.PZQ than [3H]liposomes from the total dose) was found in peritoneal cells on day 1 post therapy (p.t.) followed by a rapid decline. The kinetic of decline in these cells recovered on day 1 p.t. was studied also in vitro. Disappearance of the marker due to the breakdown of liposomes and efflux of lipids and PZQ from cells was slower for [3H]lip.PZQ in comparison with drug-free liposomes and was not completed after 4 days-incubation. Significantly increased levels of radioactivity, more in [3H]liposomes treated groups, were recorded in the liver- and peritoneal larvae between days 8-16 p.t. indicating re-utilization of cholesterol by the larvae. The data suggest that incorporation of PZQ into liposomes contributes to the enlargement of liposome average size and slows down their degradation in phagocytosing cells. In this respect, these cells could serve as the secondary circulating depots for PZQ releasing it slowly to the circulation.     

Liposomes of terbutaline sulphate: in vitro and in vivo studies

In vitro studies were conducted to understand the comparative drug diffusion pattern, across artificial membrane, of the drug and of the prepared liposomes of different liposomal membrane composition. In vivo studies were carried out to determine the extent and time-course of pulmonary tissue uptake of administered liposomes containing terbutaline sulphate(TER) on rat lungs. In vitro studies revealed that the drug released from the prepared liposomes obeys Higuchi's diffusion controlled model. Different loading doses and release patterns of drug from the liposomes can be obtained by altering the PC:CHOL ratio and incorporation of cholesterol was found to reduce permeability of the membrane. Similarly drug absorption in vivo in rat's lung following intratracheal instillation, prolonged over 12 hr by liposomal entrapment of TER. The findings of present investigation indicated that liposomally encapsulated TER can be used for pulmonary delivery for maximizing the therapeutic efficacy and reducing undesirable side effects.     

固态发酵苦荞制备多肽菌种的筛选

【目的】筛选固态发酵苦荞高产多肽及发酵产物液具有抗菌、抗氧化活性的菌株。【方法】采用米曲霉、酱油曲霉、雅致放射毛霉和少孢根霉分别对苦荞进行固态发酵,以蛋白酶活力、水解度、可溶性肽得率、抑菌率和体外自由基清除率作为筛菌指标。【结果】米曲霉固态发酵苦荞的可溶性肽得率最高达38.83%±1.18%,发酵产物液对大肠杆菌和金黄色葡萄球菌的抑菌率分别为96.62%±1.66%和97.54%±0.54%,同时羟自由基(·OH)清除率和二苯基苦味酰基苯肼自由基(DPPH·)清除率分别为55.65%±1.25%和10.84%±1.03%。对米曲霉发酵2 d发酵产物液的不同分子量分布及活性分析表明,分子量大小对抗菌及抗氧化活性有一定的影响。【结论】米曲霉可作为固态发酵苦荞制备多肽且发酵产物液具有抗菌及抗氧化活性的最佳菌株,并在多肽产量提升及抗菌、抗氧化活性的研究上具有巨大空间。     

Unilamellar liposomes with enhanced boron content

A new type of boron-rich, DSPC-free, unilamellar liposomes was formed using the novel dual-chain, ionic, nido-carborane lipid, K[nido-7-(C16H33OCH2)2CHOCH2-7,8-C2B9H11] (DAC-16), and cholesterol for encapsulation of an aqueous buffer core. Since DSPC was not necessary for the formation of stable DAC-16 liposomes, the boron concentration of these vesicles was increased dramatically to approximately 8.8 wt % in the dry lipid; these liposomes had a high bilayer boron incorporation efficiency of 98%. DSPC-free liposomes exhibited a size distribution pattern of 40-60 nm, which was in the range normally associated with selective tumor uptake. This size distribution was maintained throughout storage at room temperature for several months. Additionally, optimized liposome formulations incorporating DAC-16, DSPC, and cholesterol were identified having stable size distribution patterns after storage for more than two months at a variety of temperatures. Although animal studies indicate that DAC-16 liposomes are toxic, this new ionic nido-carborane lipid allows the formation of liposomes of high boron content for in vitro applications that require the delivery of large amounts of boron.     

Effect of cholesterol on the uptake and intracellular degradation of liposomes by liver and spleen; a combined biochemical and gamma-ray perturbed angular correlation study

We investigated the effect of cholesterol on the uptake and intracellular degradation of liposomes by rat liver and spleen macrophages. Multilamellar vesicles (MLV) consisting of distearoylphosphatidylcholine/phosphatidylserine (molar ratio 9:1) or distearoylphosphatidylcholine/cholesterol/phosphatidylserine (molar ratio 4:5:1) were labeled with [3H]cholesteryl hexadecyl ether and/or cholesteryl [14C]oleate. After i.v. injection the cholesterol-containing liposomes were eliminated less rapidly from the bloodstream and taken up to a lesser extent by the liver (macrophages) than the cholesterol-free liposomes. Assessment of the 3H/14C ratios in liver and spleen cells revealed that the cholesterol-containing liposomes are substantially more resistant towards intracellular degradation than the cholesterol-free liposomes. These results could be confirmed by measuring the release of 111In from liposomes after uptake by liver and spleen by means of gamma-ray perturbed angular correlation spectroscopy. Experiments with cultured Kupffer cells in monolayer also revealed that incorporation of cholesterol results in a decrease of the uptake and an increase of the intracellular stability of cholesteryl [14C]oleate-labeled liposomes. Finally, incubation of both types of liposomes with lysosomal fractions prepared from rat liver demonstrated a difference in susceptibility to lysosomal degradation: the cholesterol-free vesicles were much more sensitive to lysosomal esterase than the cholesterol-containing liposomes. These results may be relevant to the application of liposomes as a drug carrier system to liver and spleen (macrophages).     

西藏仲巴五彩沙漠放线菌资源勘探及生物活性筛选

【背景】细菌耐药性问题日益严峻,新抗生素的研发速度远远落后于临床需要,从特殊生境中挖掘微生物药物资源有望解决以上问题。【目的】勘探西藏仲巴五彩沙漠土壤放线菌多样性并进行生物活性筛选,为发现药用放线菌资源、开发新型抗生素奠定基础。【方法】采用8种分离培养基,通过平板稀释涂布法分离放线菌;根据分离菌株的16S r RNA基因序列同源性分析放线菌多样性;采用PCR技术对分离的放线菌菌株进行II型聚酮合酶(PKS-II)酮缩酶结构域KS、非核糖体多肽合成酶(NRPS)腺苷酸化结构域A、安莎类抗生素生物合成前体3-氨基-5-羟基-苯甲酸合酶(AHBA)保守区、黄素腺嘌呤二核苷酸卤化酶(Halo)保守区抗生素生物合成基因检测;对生物合成基因检测阳性的菌株进行液体发酵,发酵液经乙酸乙酯萃取、菌体经丙酮浸提,获得提取浓缩物样品进行抑菌活性和抗氧化活性筛选。【结果】从4份土样中分离纯化到231株放线菌,分布于7个属,其中链霉菌为优势菌属。68株放线菌的生物合成基因分析显示至少具有1种生物合成基因簇,其中6株同时具有4种生物合成基因簇;进一步的抑菌活性检测显示所有检测的菌株至少表现为对1株检定菌具有抑菌活性,其中8株具有广谱抗菌活性;抗氧化活性筛选结果为13株显示总抗氧化能力阳性,10株具有较好的羟自由基清除能力,3株显示较强的氧自由基清除能力。【结论】西藏仲巴五彩沙漠土壤中含有较丰富的放线菌药用资源,具有从中发现放线菌新菌种和开发新抗生素的潜力。     

Preparation and in vitro evaluation of liposomal/niosomal delivery systems for antifungal drug clotrimazole

Clotrimazole, an imidazole derivative antifungal agent is widely used for the treatment of mycotic infections of the genitourinary tract. In order to develop alternative formulation for the vaginal administration of clotrimazole to provide sustained and controlled release of appropriate drug for local vaginal therapy, liposomes/niosomes were evaluated as delivery vehicles. To optimize the preparation of liposomes/niosomes with regards to size and entrapment efficiency, multilamellar liposomes/niosomes containing drug were prepared by lipid hydration method. The ability of the systems to deliver clotrimazole into and through the mucosa was evaluated in vitro using rabbit vaginal mucosa with vertical Franz diffusion cells. The in vitro permeation data showed that the liposomes/niosomes system increased the clotrimazole total penetration through the vaginal mucosa by 1.6, 1.5-fold, the accumulation of clotrimazole into the mucosa was increased by 3.1, 2.3-fold, respectively, as compared with control during 24 hr. These results suggest that the studied liposomes/niosomes systems may be appropriate vesicles for the vaginal mucosa delivery of clotrimazole for local vaginal therapy.