At present days drugs are formulated by using different novel drug delivery system (NDDS) which are used for targeting drugs to different organ systems and for controlled /sustained release of drug from the dosage forms. The NDDS can be used to overcome many disadvantages of conventional dosage forms like poor bioavailability, first pass effect, systemic toxicity, degradation of drug in stomach etc. which results in decreased biological activity of the drugs. Vesicular system is one of the important NDDS studied since a lot of time, of which main importance was given to liposomes. Due to the unstability of phospholipids (used for the formulation of liposomes) on storage was replaced with non ionic surfactants. Niosomal vesicles were prepared by using non ionic surfactants and were first reported in cosmetic industry. Niosomes are used as carrier systems for the delivery of most of the drugs, biologically active agents, hormones and antigens for the better treatment. The present review involves a detailed description about the drug delivery through niosomal formulation.
technique. They carried out photomicroscopy, transmission electron microscopy and particle size analysis for evaluation of vesicles. They reported that niosomal Gentamicin sulphate shows a high retention as compared to the free drug solution in-vitro release study. Authors also carried out ocular irritancy study and concluded that there were no signs of irritation 49 . CONCLUSION: The vesicular drug delivery has its distinctive advantages due to its novel structure. The strategic role of bilayer vesicles has been investigated by many researchers over the time. The critical structure of human eye and its anatomical as well as physiological barriers can be more conveniently overcome by vesicular drug delivery system. The bio- adhesive nature of phospholipids and non-irritating nature of non-ionic surfactants have laid detailed research on vesicles as ocular drug delivery system. The potential action of vesicles drug delivery system will lead to drastically reduced therapy time and excellent patient compliance.
The Convectional method was first described in detail by Bangham et al for the preparation of MLVs. In the procedure; the phospholipids are dissolved in an organic solvent (usually a chloroform/methanol mixture) and deposited from the solvents as a thin film on the wall of a round bottom flask by use of rotary evaporation under reduced pressure. MLVs form spontaneously when an excess volume of aqueous buffer containing the drug is added to the dried lipid film. [22,23] Drug containing liposomes can be separated from nonsequestered drug by centrifugation of the liposomes or by gel filtration. The time allowed for hydration of the dried film and conditions of agitation are critical in determining the amount of the aqueous buffer (or drug solution) that will be entrapped within the internal compartments of the MLVs. For instance, it is reported that more of the aqueous phase can be sequestered when the lipid is hydrated for 20 hours with gentle shaking, compared with a hydration period of two hours, with vigorous shaking of the flask, even though size distribution of the MLVs was unaffected . This means that slow hydration is associated with greater entrapment of aqueous volume. [24,25]
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www.wjpr.net Vol 4, Issue 4, 2015. 1672 Vesicular systems have been receiving a lot of interest as a carrier for advanced drug delivery. Encapsulation of the drug in vesicular structures is one such system, which can be expected to prolong the duration of the drug in systemic circulation and to reduce the toxicity by selective up taking.  Drug delivery systems using colloidal particulate carriers such as liposomes or niosomes have proved to possess distinct advantages over conventional dosage forms because the particles can act as drug reservoirs, can carry both hydrophilic drugs by encapsulation of hydrophobic drugs by partitioning of these drugs into hydrophobic domains and modification of the particle composition or surface can adjust the drug release rate and/or the affinity for the target site. The vesicles in a dispersed aqueous system may suffer from some chemical problems associated with degradation by hydrolysis or oxidation as well as physical problems as sedimentation, aggregation, or fusion of liposomes during storage.  Two novel approaches were adopted in dealing with these problems to develop the proliposomes and to develop Niosomes using non-ionic surfactants alternatives to phospholipids in preparing vesicles. Niosomes exhibit good chemical stability during storage but aqueous suspension of noisome may exhibit problems of physical stability such as aggregation, fusion, leaking of entrapped drugs, or hydrolysis of encapsulated drugs, thus limiting their shelf life.  The latest approach in the field of vesicular delivery is to combine the two previously mentioned techniques by extending the pro-vesicular approach to niosomes through the formation of “proniosomes” which are converted to niosomes upon hydration. [1,2]
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Lipid based drug delivery systems have been examined in various studies and exhibited their potential in controlled and targeted drug delivery. Pharmacosomes, a novel vesicular drug delivery system, offering a unique advantage over liposomes and niosomes, and serve as potential alternative to these conventional vesicles. They constitute an amphiphilic phospholipid complex with drug bearing an active hydrogen atom covalently that bind to phospholipids. They provide an efficient delivery of drug required at the site of action, which ultimately reduces the drug toxicity with reduced adverse effects and also reduces the cost of therapy by imparting better biopharmaceutical properties to the drug, resulting in increases bioavailability, especially in case of poorly soluble drugs. As the system is formed by binding the drug (pharmakon) to carrier (soma), they are termed as pharmacosomes. Depending upon the chemical structure of the drug lipid complex they may exist as ultrafine vesicular, micellar and hexagonal aggregate. Drug having active hydrogen group such as carboxyl, hydroxyl group can be esterified to lipids, resulting in amphiphilic compound. Pharmacosomes are widely used as carriers for various non-steroidal anti-inflammatory drugs, proteins, cardiovascular and antineoplastic drugs. The release of drug from pharmacosomes is generally governed by the process of enzymatic reaction and acid hydrolysis. Here, in the present review paper we have discussed the potential of pharmacosomes as a controlled and targeted drug delivery system and highlighted the method of preparation and characterization.
Gemcitabine is a potent anticancer drug approved for the treatment of pancreatic, non-small-cell lung, breast, and ovarian cancers. Gemcitabine is a highly reactive molecule and binds extensively to plasma and tissue proteins leading to a fast inactivation of a large part of the administered dose. Thus, the clinical use of Gemcitabine faces two major problems, serious dose-limiting toxicities and rapid inactivation of the drug in the circulation. Both problems could possibly be prevented by shielding of the drug from the extracellular environment by means of a lipid coating. In the present investigation Gemcitabine loaded long circulating liposomes were prepared by thin film hydration method. By using different concentrations of PEGylated phospholipids, from the preliminary in vivo work, it was observed that stealth liposome’s formulation was better than free Gemcitabine. Stealth liposome’s formulation decreased the volume of solid tumor as well as ascites volume, decreased average body weight and increased the life span. In vivo pharmacokinetic studies were carried out in lymphoma bearing mice and the drug was detected in plasma even after 24 hours. This reveals that the stealth liposome’s formulation had improved stability in the biological fluids. Tissue distribution studies done in the drug loaded long circulating liposome’s showed preferential drug targeting to liver followed by spleen, lungs, and kidneys. Higher concentration of drug was targeted to the organs after administering the dose in the form of long circulating liposomes except in the heart. Drug levels in the heart are closely related to the inherent cardiac toxicity of Gemcitabine. Therefore using liposomal Gemcitabine formulation could reduce the cardiac toxicity of Gemcitabine.
liposomes and niosomes, especially since niosomes are prepared from uncharged single-chain surfactant and cholesterol, whereas liposomes are prepared from double- chain phospholipids (neutral or charged). The concentration of cholesterol in liposomes is much more than that in niosomes. As a result, drug entrapment efficiency of liposomes becomes lesser than niosomes. Besides, liposomes are expensive and its ingredients, such as phospholipids are chemically unstable because of their predisposition to oxidative degradation; moreover, these require special storage and handling and purity of natural phospholipids is variable. Niosomal drug delivery is potentially applicable to many pharmacological agents for their action against various diseases. It can also be used as vehicle for poorly absorbable drugs to design the novel drug delivery system. It enhances the bioavailability by crossing the anatomical barrier of gastrointestinal tract via transcytosis of M cells of Peyer's patches in the intestinal lymphatic tissues 8 . The niosomal vesicles are taken up by
Drug delivery system using colloidal particulates carriers such as liposomes 1 and niosomes 2 have distinct advantages over conventional dosage forms. These carriers can act as drug reservoirs and modification of their composition or surface can Be used for drug targeting. In disperse aqueous system liposomes have problems associated with degradation by hydrolysis or oxidation as well as sedimentation, aggregation or fusion of liposomes during storage and problems in their sterilisation. Niosomes are unilamellar or multilamellar vesicles are capable of entrapping hydrophilic and hydrophobic solutes. 3 Niosomes are promising drug carriers as they posses greater stability and lack of many disadvantages associated with liposomes such as high cost and the variable purity problems of phospholipids. Large scale production of niosomes without the use of acceptable solvents. 4,5
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Liposomes are microscopic spheres made up of lipids usually phospholipids. They spontaneously form when lipids are dispersed in aqueous media. They can be constructed so that they entrap quantities of highly polar and relatively small solutes within the aqueous compartment and lipophobic substances within the lipid bi-layers. Owing to their stability, biocompatibility, easy scaling up and capability to carry different lead compounds as cargo, different formulations of liposomal drugs have been optimized to target drug to specific site of interest against various diseases (Allen and Cullis, 2013). Following the systemic administration, liposomes are accumulated in the reticuloendothelial system (RES) such as spleen, liver, lungs, kidney, lymph nodes and bone marrow, and cleared up by residential macrophages. In accordance with earlier report, the best clinical outcomes have been gained by the liposomal formulation AmBisome than lipid complex formulations of AmpB regarding efficacy in in vivo evaluations (Larabi et al., 2003). Recently, cholesterol has been substituted by ergosterol containing 50% total lipids molarity in liposome formulations as cholesterol enhances the growth of leishmania promastigotes and has been named as Kalsome TM 10 whose efficacy was found to be very potent in apoptotic cell death in Leishmania parasites (Mishra et al., 2013; Asad et al., 2015; Shadab et al., 2017). A lot of anti- leishmanial antimonials have been formulated in liposomes and their biological efficacies have been evaluated (New et al., 1978). Furthermore, liposomes have been modified with anionic and neutral surface charges to test their efficacies (Carter et al., 1989), but only cationic phosphatidyl choline-
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Niosomes are novel drug delivery system in which serves as drug depots in the body which release the drug in a controlled manner through its bilayer providing sustained release of the enclosed drug. Niosomes are non-ionic surfactant vesicles obtained by hydration of synthetic non-ionic surfactants, with or without incorporation of cholesterol or other lipids. The niosomes are very small, and microscopic in size . Their size lies in the nanometric scale. They are vesicular systems similar to liposomes that can be used as carriers of amphiphilic and lipophilic drugs. One of the reasons for preparing niosomes is assumed higher chemical stability of the surfactants than that of phospholipids, which are used in the preparation of liposomes. Due to the presence of ester bond, phospholipids are easily hydrolysed .
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Topical drug delivery system is considered to be one of the most relevant routes for treating skin diseases efficaciously. Despite of having the advantages of self-administration, patient compliance and reduction in adverse effects systemically, this system has the limitation of slow diffusion across the stratum corneum 1 and the barrier property of the skin limits the delivery of the drug through the skin 2 .Therefore several approaches have been used to weaken this skin barrier and to enhance the administration of the drug through the skin. One of these approaches is the use of vesicle formulations as skin dermal system 3 . The various vesicular systems investigated, ethosomal vesicles have been found to be capable enough in enhancing permeation of topical agents to the deeper tissues through the stratum corneum 4 . Enhanced permeation through these vesicles is not only due to the presence of ethanol but also due to the fact that these vesicles are highly deformable and malleable that allows their better penetration across the skin 5 . Ethosomes, soft vesicles consisting of biocompatible ingredients, phospholipids, ethanol and water, were introduced by Touitou 6, 7 . According to the suggested mechanism of skin permeation enhancement by ethosomes, ethanol fluidizes the lipid bilayers of the stratum corneum and of the ethosome, resulting in
The concepts of sphingosomes as drug or bioactive carrier still need further optimization. Researchers all world continue to put in their in improving vesicular system by making them steady in nature to prevent leaching of content, oxidation and their uptake by natural defence machanism. Genetic engineering aspect can be coupled to give newer dimension to the existing cellular drug carrier concept. Their potential pharmaceutical application include immobilization of enzyme, masking the taste of drug, enhancement of gastrointestinal absorption and as carrier for sustained release and transdermal drug delivery, treatment of drug overdosing. With the evolution of various newer techniques of preparation, stabilization, characterization of these system, they can serve as potential carrier for drug cosmetic and pharmaceutical agents.
The objective of the study is to evaluate the potential of novel vesicular drug carriers for bioavailability enhancement. Novel vesicular drug delivery carriers intend to deliver the drug at a rate directed by need of body during the period of treatment, and channel the active entity to the site of action. Encapsulation of drug in vesicular structures prolongs the existence of drug in systemic circulation and reduces the toxicity, if selective uptake can be achieved. Vesicular drug delivery systems have been used to improve the therapeutic index, solubility, stability and rapid degradation of drug molecule. This system reduces the cost of therapy by bioavailability improvement of medication, especially in case of poorly soluble drugs. Thus a number of novel vesicular drug delivery systems have been developed that enhance the bioavailability and provide sustained or controlled release of drug. The focus of this review is to discuss various lipoidal and non-lipoidal vesicles with special emphasis on the bioavailability enhancement of drugs.
5. Other approach: Another approach for producing pharmacosomes was recently developed in which a biodegradable micelle forming drug conjunct was synthesized from the hydrophobic drug a driamycin and a polymer composed of polyoxyethylene glycol and polyaspartic acid. This method has the benefit that although it may be possible to dilute out the micelle, the drug will probably not precipitate because of the water solubility of the monomeric drug conjunct Approaches have been done to attach drugs to various glyceride-like groups, and the resulting amphiphilic molecules have been spontaneously dispersed. They were labelled pharmacosomes because of their tendencies to form unilamellar vesicles. It was suggested that these molecules should enhance lymph transport.
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There has been keen interest in the development of a novel drug delivery system. Novel drug delivery system aims to deliver the drug at a rate directed by the needs of the body during the period of treatment, and channel the active entity to the site of action. At present, no available drug delivery system behaves ideally achieving all the lofty goals, but sincere attempts have been made to achieve them through novel approaches in drug delivery. A number of novel drug delivery systems have emerged encompassing various routes of administration, to achieve controlled and targeted drug delivery. Encapsulation of the drug in vesicular structures is one such system, which can be predicted to prolong the existence of the drug in systemic circulation, and reduce the toxicity, if selective uptake can be achieved. Consequently a number of vesicular drug delivery systems such as liposomes, niosomes, transfersomes, and pharmacosomes were developed. Advances have since been made in the area of vesicular drug delivery, leading to the development of systems that allow drug targeting, and the sustained or controlled release of conventional medicines. The focus of this review is to bring out the application, advantages, and drawbacks of vesicular systems.
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Spreadability 17,21 : A modified apparatus suggested was used for determining spreadability. The spreadability was measured on the basis of slip and drag characteristics of the gels. The modified apparatus was fabricated and consisted of two glass slides, the lower one was fixed to a wooden plate and the upper one was attached by a hook to a balance. The spreadability was determined by using the formula: S=ml/t, where S, is spread ability, m is weight in the pan tied to upper slide and t is the time taken to travel a specific distance and l is the distance traveled. For the practical purpose the mass, length was kept constant and‘t’ was determined. The measurement of spreadability of each formulation was in triplicate and the average values are presented. Drug content 17,18 : 1 gm. of the prepared gel was mixed with 100 ml. of ethyl alcohol. Aliquots of different concentrations were prepared by suitable dilutions after filtering the stock solution and the absorbance was measured at 486 nm. Drug content was calculated by linear regression analysis of the calibration curve. In-vitro diffusion study 20,21 : An in-vitro drug release study was performed using modified Franz diffusion
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The proliposomes are prepared by carrier method using film deposition technique. From the earlier reference drug and lecithin in the ratio of 0.1:2.0 can be used as an optimized one. The proliposomes are prepared by taking 5mg of mannitol powder in a 100 ml round bottom flask which is kept at 60-70°c temperature and the flask is rotated at 80-90 rpm and dried the mannitol at vacuum for 30 minutes. After drying, the temperature of the water bath is adjusted to 20- 30°C. Drug and lecithin are dissolved in a suitable organic solvent mixture, a 0.5ml aliquot of the organic solution is introduced into the round bottomed flask at 37°C, after complete drying second aliquots (0.5ml) of the solution is to be added. After the last loading, the flask containing proliposomes are connected in a lyophilizer and subsequently drug loaded mannitol powders (proliposomes) are placed in desiccators over night and then sieved through 100 mesh. The collected powder is transferred into a glass bottle and stored at the freeze temperature until characterization. 8. By using free film method: 61 Free film of cellulose acetate is prepared by casting on mercury surface. A polymer solution 2% w/w is to be prepared by using chloroform. Plasticizers are to be incorporated at a concentration of 40% w/w of polymer weight. Five ml of polymer solution was poured in a glass ring which is placed over the mercury surface in a glass petri dish. The rate of evaporation of the solvent is controlled by placing an inverted funnel over the petri dish. The film formation is noted by observing the mercury surface after complete evaporation of the solvent. The dry film will be separated out and stored between the sheets of wax paper in a desiccator until use. Free films of different thickness can be prepared by changing the volume of the polymer solution.
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which is insignificant and also an increase in vesicle size was observed for the optimized batch at 25 ± 1ºC.Thus is due to the fact that a higher temperature the vesicle tent to collide with each other due to increase in the mean kinetic energy and as result they fuse with each other resulting in the increase in the size. During collision, fusion and reformation of the vesicles there is loss of slight amount of the drug because of the bilayer disruption and hence very less or insignificant loss of drug occurs. Result suggests that keeping the liposomal product in refrigeration conditions minimizes stability problems of liposomal gel and hence the best suited temperature for liposomal gel is 4.0 1C.
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For releasing the drug in a pulsatile manner, another way can be the externally regulated systems in which drug release is programmed by external stimuli like magnetism, ultrasound, electrical effect and irradiation. Magnetically regulated system contains magnetic beads in the implant. On application of the magnetic field, drug release occurs because of magnetic beads. Saslawski et al. developed different formulation for in vitro magnetically triggered delivery of insulin based on alginate spheres23. In case of ultrasonically modulated systems, ultrasonic waves causes the erosion of the polymeric matrix thereby modulating drug release. Miyazaki et al evaluated the effect of ultrasound (1 MHz) on the release rates of bovine insulin from ethylenevinyl alcohol copolymer matrices and reservoir-type drug delivery systems in which they found sharp drop in blood glucose levels after application of ultrasonic waves24. Also irradiation with light rays the desired drug release pattern. Mathiowitz et al developed photochemically controlled deliver y systems prepared by interfacial polymerization of polyamide microcapsules. For this purpose, azo bis isobutyronitrile (AIBN), a substance that
Since 1981, transdermal drug delivery systems have been used as safe and effective drug delivery devices. Their potential role in controlled release is being globally exploited by the scientists with high rate of attainment. If a drug has right mix of physical chemistry and pharmacology, transdermal delivery is a remarkable effective route of administration. Due to large advantages of the TDDS, many new researches are going on in the present day to incorporate newer drugs via the system. A transdermal patch has several basic components like drug reservoirs, liners, adherents, permeation enhancers, backing laminates, plasticizers and solvents, which play a vital role in the release of drug via skin. Transdermal patches can be divided into various types like matrix, reservoir, membrane matrix hybrid, micro reservoir type and drug in adhesive type transdermal patches and different methods are used to prepare these patches by using basic components of TDDS. After preparation of transdermal patches, they are evaluated for physicochemical studies, in vitro permeation studies, skin irritation studies, animal studies, human studies and stability studies. But all prepared and evaluated transdermal patches must receive approval from FDA before sale. Future developments of TDDSs will likely focus on the increased control of therapeutic regimens and the continuing expansion of drugs available for use. Transdermal dosage forms may provide clinicians an opportunity to offer more therapeutic options to their patients to optimize their care .