INTRODUCTION:

1. Liposomes:

The name liposome is gotten from Two Greek words: 'Lipos' which means fat 'Soma' which means body. A liposome can be Formed at a variety of sizes as unilamellar or multi-lamellar development, and its name identify with its basic structure squares, phospholipids and not to its size. In 1961, the British haematologistDr. Alec D Bangham found the liposomes which were then got distributed in 1964, at the Babraham establishment, in Cambridge.

In liposomes the particles of medication can either be intercalated into the bilayers of lipid or it very well may be encapsulated in aqueous space. The specific area of the medication will rely on its physicochemical qualities and the structure of lipid.

The liposomes are framed by dispersed the phospholipids in water which at that point structures closed structure with inward watery condition limited by bilayer layers of phospholipids. Around 40 years back Bangham and collaborators characterized Liposomes as the Vesicle of circular shape that can be delivered from cholesterols, non-toxic surfactants, sphingolipids, Glycolipids and long chain unsaturated fats. In science, organic chemistry and medication the film protein has become the flexible instrument.^1,2

Reasons to use Liposomes as Drug carriers³:

Solubilization-As some of drug are lipophilic and cannot be administered by intravenously so by making them into liposomes it becomes easy to administer.

Protection:

The drug inside the liposomes are inaccessible to external metabolizing enzymesi.e. the entire dose of drug is not directly exposed to the body component.

Duration of action:

By slow release mechanism of drug the liposomes can prolong the drug action. The distribution of the drug through the body changes due to directly potential targeting options.

Internalization:

Liposomes are endocytosed or Phagocytosed by cells, opening up chances to utilize liposome subordinate medications. Lipid based structures (not really liposomes) are likewise ready to bring plasmid material into the cell through a similar component (non-viral transfection frameworks).

Amplification:

Liposomes can be utilized as adjuvant in immunizationplans.

Advantages:

· Itprovides controlled drug delivery.

· It is biodegradable, biocompatible and flexible.

· It is non-ionic.

· It can carry both water and lipid soluble drugs.

· The drugs can be stabilized from oxidation.

· It should improve the protein stabilization.

· It provides controlled hydration.

· It provides sustained release.

· It provides targeted drug delivery or site-specific drug delivery.

· Stabilization of entrapped drug from hostile environment.

· Alter Pharmacokinetics and pharmacodynamics of drugs.

· It can be administered through various routes.

· It can incorporate micro and macro molecules.

· It acts as reservoir of drugs.

· The therapeutic index of drug is increased.

· Site avoidance therapy.

· It can modulate the distribution of drug.

· It should be direct interaction of the drug with cell.

Disadvantages:

· Product cost is high.

· Leakage and fusion of encapsulated drug or molecules.

· Sometimes phospholipids undergo oxidation and hydrolysis like reaction.

· Short half life

· Low solubility

· Inadequate stability due to uptake by reticulo-endothelial system.

1.2 Designing of Liposomes^4,5,6:

Liposomes with or without captured mixes, can be intended to

· Release their substance when they arrive at a particular temperature.

· Release their substance at a particular pH esteem.

· Target certain tissues or cell types by changing the sorts of lipids in the liposome.

· Target tissues, cell types proteins by joining antibodies to the surface.

· Avoid certain tissues or cells by joining complex sugar to the surface.

· Evenly disseminate fat-dissolvable (oil-like) mixes, for example, certain nutrient, cell reinforcements, anti-microbials, flavors and so on which regularly can't be blended in water-based items including most nourishments.

· Fuse with cells, which is significant in conveying DNA to a cell.

· Serve as model cell films making it simpler to examine explicit cell procedures and how certain atoms, for example, drugs, interface with cells.

· Protect mixes from acidic and enzymatic corruption in the stomach and digestive system by utilizing certain particles to cover the liposomes.

· Protect mixes, for example, nutrients and cell reinforcements from untimely oxidation for expanded time span of usability.

· Enhance the intestinal retention of mixes by covering with specific particles.

· Delivery tranquilizes legitimately to the lung tissue by inward breath of liposomes.

· Carry fluorescent colours or different sorts of atoms which permit the liposomes to be followed in the framework to which they are included.

1.3 Classifications^7-10

Based on composition and mode of drug delivery:

Conventional liposome or anionic liposome:

Made out of neutral or contrarily charged phospholipids and cholesterol. Subject to covered pit endocytosis, substance at last conveyed to Liposome's on the off chance that they don't combine with the endosomes, short dissemination half-life, dose dependent pharmacokinetics.

pH sensitive liposome:

Numerous plans of pH-sensitive liposome's have been created in the past few years. pH-sensitive liposomes are shaped from lipids which embrace a lamellar stage at pH around 7.4 (physiological pH). At the point when the pH is diminished to a basic worth (around 5.5) 250 the liposome will combine with the endosomal film. Because of the combination of the liposome with the endosomal layer the substance of the liposome (drugs) are discharged into the cytosol. The explanation behind the combination at the lower pH is the change from lamellar to hexagonal HII stage. At the same time film deformity happens which bring about the arrival of the epitomized substance into the liposome-encompassing compartment, for example, endosome. The combination of liposome's with cell layers can be observed by fluorescence resonance energy transfer (FRET).

Epitome of Genetic Materials into Liposomal Systems or Cationic Liposome:

Made out of cationic lipids, Fuse with cell or endosome films; reasonable for conveyance of negatively charged macromolecules (DNA, RNA); simplicity of arrangement, structurally unstable; toxic when given in high dose, restricted to local administrations E.g. DODAC.

Long circulating or stealth liposome:

Made out of neutral high progress temperature lipid, cholesterol and 5-10% of PEG-DSPE. Hydrophilic surface covering, low ionization and subsequently low pace of take-up by RES long circling half-life (40 hrs); Dose independent Pharmacokinetics.

Immuno liposome:

Ordinary or stealth liposome's with joined Antibody or Recognition Sequence. Subject to receptor interceded endocytosis, cell specific binding (targeting); can discharge substance extra cell close to the target tissue and medications diffuse through plasma film to produce their effects.

Magnetic Liposome:

Made out of P.C, cholesterol and limited quantity of a direct chain aldehyde and colloidal particles of attractive Iron oxide. These are liposome's that indigenously contain restricting locales for attaching different particles like antibodies on their outside surface. Can be made use by an outside vibrating attractive field on their purposeful, on location, rapture and immediate release of their components.

Temperature (or) heat sensitive liposome:

Made out of Dipalmitoyl P.C. These are vesicles indicated most extreme discharge at 41ᵒ, the stage change temperature of Dipalmitoyl P.C. Liposome's discharge the entangled substance at the target cell surface upon a concise warming to the stage progress temperature of the liposome layer.

Fluorescent Liposome:

Can be made from different fluorescent probes such as

· Fixable polartracers

· Lucifer yellow derivatives

· Cascade blue and Alexa Fluor 405 derivatives

· Non fixable polar tracers

· Fluoesceinderivatives

· Sulforhodamines

· Polysulfonatedpyrenes

· Lanthanide Chelates

Fatty Acid Labeled Lipids:

· GlycerolBased

· Phosphatidylcholine

· PhosphatidicAcid

· Phosphatidylethanolamine

· Phosphatidylglycerol

· Phosphatidylserine

Sphingosine Based:

· Sphingosine

· Sphingosine-1-Phosphate

· Ceramide

· Sphingomyelin

· Phytosphingosine

· GalactosylCerebroside

Headgroup Labeled Lipids:

Glycerol Based

· Phosphatidylethanolamine

· Phosphatidylethanolamine (Lissamine RhodamineB)

· Dioleoyl Phosphatidylethanolamine (Dansyl, Pyrene, Fluorescein)

· Phosphatidylserine

· Phosphatidylserine (Dansyl)

Other Labeled Lipids:

· 25- NBDCholesterol⁹.

Surface Modification ofLiposome’s

Change of the liposomal surface is a significant device for controlling the organic properties of liposomes. Connection of certain particular ligands, for example, peptides, proteins (for example antibodies), hormones, sugars, metals (attractive liposome) makes liposome's focused on; covering liposome's with polymers, for example, PEG (poly (ethylene glycol) or poly ethylene Glycolyted liposome enable the liposome's to flow longer in body without being perceived by reticulum endothelial framework cells; connection of complexity specialist changes over liposome into a powerful diagnostic tool.

Based on Size and Number of Lamellae:

Multi lamellar vesicles (M.L.V):

Size: 0.1 - 0.3 micro meters

Have more than one bilayer; moderate aqueous volume to lipid proportion 4: 1 mole lipid. More encapsulation of lipophilic medication, precisely stable upon long term storage, quickly cleared by R.E.S, valuable for focusing on the cells of R.E.S, simplest technique prepared by film hydration of lipids in presence of anorganic sovlent.

1. Oligo lamellar vesicles or Paucilamellar vesicles Intermediate between L.U.V and MLV

2. Multi vesicular liposome

Separate compartments are available in a solitary M.L.V.

3. Stable Pluri

4. lamellar vesicles

Have unique physical and natural properties because of osmotic pressure.

Large Unilamellar Vesicles (L.U.V):

Size: 0.1 - 10 micro meters

Have single bilayer, high fluid volume to lipid proportion (7:1 mole lipid), valuable for hydrophilic medications, high capture of micromolecules; quickly cleared by R.E.S. Prepared by detergent dialysis, ether injection, reverse phase evaporation or active loading techniques.

Small Unilamellar Vesicles (S.U.V):

Size: 0.1 micro meters.

Single bilayer, homogeneous in size, thermodynamically unstable, susceptible to aggregation and fusion at low or no charge, limited capture of macro molecules, low fluid volume to lipid proportion (0.2: 1.5: 1 mole lipid) prepared by decreasing the size of M.L.V or L.U.V utilizing probesonicator or gas extruder or by active loading or solvent injection method.

Figure 3: Types of lamellae^10,4

Small Molecules Encapsulated intoLiposomes:

· Clodronate or Dichloromethylenediphosphonic acid (DMDP)

· Antibiotic EncapsulatedLiposomes

· Anti-Tumor Drugs EncapsulatedLiposomes

· AntioxidantLiposomes

· NSAIDs encapsulatedliposomes

· ATP EncapsulatedLiposomes

· Hemoglobin encapsulated Liposomes (artificialblood)

· Vitamin EncapsulatedLiposomes

Table 2: Classification of liposomes based on size

Type	Usual Size	Characteristics
MLV (Multilamellar vesicles)	>0.1 μm	More than one bilayer; greater encapsulation of lipophilic drugs; mechanically stable on long term storage; rapidly cleared by RES
LUV (Large unilamellar vesicles)	>0.1 μm	Single bilayer; useful for hydrophilic drugs; high capture of macromolecules; rapidly cleared by RES
SUV (Small unilamellar vesicles)	<0.1 μm	Single bilayer; homogenous in size; thermodynamically unstable; long circulation half life

Table 3: Based on Method of Preparation^11,4

Method of preparation	Vesicle type
Single or oligo lamellar vesicle made by reverse phase evaporation Method	REVS
Multi lamellar vesicle made by reverse phase evaporation method	MLV-REV
Stable pluri lamellar vesicle	SPLV
Frozen and thawed multi lamellar vesicle	FATMLV
Vesicle prepared by extrusion technique	VET
Dehydration- Rehydration method	DRV

1.2.6 Basic components of liposomes:

1.2.6.1 Phospholipids:

Glycerol containing phospholipids are most basic used fragment of liposome definition and address more prominent than half of weight of lipid in organic layers. These are gotten from Phosphatidic corrosive. The establishment of the molecule is glycerol moiety.

Examples of phospholipids are

 Phosphatidyl choline (Lecithin) – PC

 Phosphatidyl ethanolamine (cephalic) – PE

 Phosphatidyl serine (PS)

 Phosphatidyl inositol (PI)

 Phosphatidyl Glycerol (PG)

For stable liposomes, immersed fatly acids are used. Unsaturated fats are not used generally Bilayer formers Phospholipids that are the critical sections of the organic layers are the structure squares of the liposomes. The phospholipids have roundedshape owning to the proximity of two acyl affixes associated with a polar head and on hydration, results into a bilayered layer. Two sorts of phospholipids are there for examplephosphodiglycerides and sphingolipidsalongside their comparing hydrolysis items.

Unsaturated phospholipids:

1- Stearoyl-2-Linoleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt);

 Dioleaylphosphotidylcholine

 Sphingolipids: Shingomyelin

 Glycosphingolipids: Gangliosides

 Steroids: Cholesterol

Polymeric material: Lipids conjugated to diene, methacrylate, and thiol gathering Charge prompting lipids: Dioctadecyl dimethyl ammonium bromide/chloride (DODAB/C); Dioleoyl trimethylammonium propane (DOTAP)

Spine is sphingosine or a related base. These are noteworthy constituents of plant and animal cells. This contain 3 trademark building squares

 A mol of Fatty Acid

 A mol of sphingosine

 A head group that can differ from simple alcohols, for example, choline to complex carbohydrates.

 Sphingolipids – Sphingomyelin. Glycosphingo lipids.

 Gangliosides – found on grey matter, utilized as a minor part for liposome production.

Sterols:

Cholesterol and its derivatives are often includedfor liposomes for

 Decreasing the fluidity or microviscocity of the bilayer

 Reducing the penetrability of the film to water dissolvable atoms

 Stabilizing the layer within the sight of biological fluids, for example, plasma. (This impact utilized in formulation of i.v. liposomes)

Liposomes without cholesterol are known to collaborate quickly with plasma protein, for example, albumin, transferring, and macroglobulin. These proteins will in general concentrate mass phospholipids from liposomes, consequently exhausting the external monolayer of the vesicles leading physical instability. Cholesterol appears to generously diminish this sort of interaction. Cholesterol has been known as the mortar of bilayers, on the grounds that by goodness of its molecular shape and solubility properties, it occupies in void spaces among the Phospholipids particles, tying down them all the more strongly into the structure. The OH group at third position gives little Polar head gathering and the hydrocarbon chain at C17 becomes non polar end by these particles, the cholesterol intercalates in the bilayers.

Synthetic phospholipids

E.g: for saturated phospholipids are

 Dipalmitoyl phosphatidyl choline (DPPC)

 Distearoyl phosphatidyl choline (DSPC)

 Dipalmitoyl phosphatidyl ethanolamine (DPPE)

 Dipalmitoyl phosphatidyl serine (DPPS)

 Dipalmitoyl phosphatidic acid (DPPA)

 Dipalmitoyl phosphatidyl glycerol (DPPG)

E.g.: For unsaturated phospholipids

 Dioleoyl phosphatidyl choline (DOPC)

 Dioleoyl phosphatidyl glycerol (DOPG)

Polymeric materials:

Synthetic phospholipids with diactylenicgroup in the hydrocarbon chain polymerize when exposed to U.V, leading to formation of polymerized liposomes having fundamentally higher permeability barriers to entrapped aqueous drugs.

E.g.: For other Polymer sable lipids will be lipids containing conjugated diene, Methacrylate and so forth. Additionally, a few Polymer sable surfactants are likewise incorporated.

Polymer bearing lipids:

Stability of repulsive interactions with macromolecules is represented for the most part by repulsive electrostatic powers. This repulsion can be instigated by covering liposome surfaces with charged polymers. Non-ionic and water compatible polymers like polyethylene oxide, polyvinyl alcohol, and Polyoxazolines gives higher solubility. But adsorption of such copolymers containing hydrophilic fragments with hydrophobic part leads to liposome spillage, so best outcomes can be accomplished by covalently joining polymers to phospholipids.

E.g.: Diacyl Phosphatidyl ethanolamine with PEG polymer connected by means of a carbon at or succinate bond. The level of polymerization changes from 15-120 units. Longer polymers offer ascent to aqueous solubility of polymer lipids and their first expulsion from layers in non –equilibrium conditions. While shorter polymers don't offer enough repulsive pressure in light of the fact that Vander Waal's attraction is a long range force12,7.

Cationic lipids:

E.g.: DODAB/C – Dioctadecyl dimethyl ammonium bromide or chloride

DOTAP–Dioleoyl propyl trimethyl ammonium chloride–this is ananalogue of DOTAP and different others including different analogues of DOTMA and cationic derivatives of cholesterol.

Other Substances:

Variety of different lipids of surfactants are utilized to shape liposomes

 Many single chain surfactants can shape liposomes on mixing in with cholesterol

 Non-ionic lipids

 A variety of Polyglycerol and Polyethoxylated mono and dialkyl amphiphiles utilized basically in cosmetic preparation.

 Single and double chain lipids having fluoro carbon chains can shape entirely stable liposomes

 Sterylamine and Dicetyl phosphate

 Incorporated into liposomes in order to give either a negative or positive surface charge to these structures

 A number of compounds having a single long chain hydrocarbon and an ionic head group saw as equipped for shaping vesicles. These incorporate quaternary ammonium salts of dialkylphosphates.

Charge inducers and steric stabilizers

Stearylamine, dicetylphosphate, solulan C-24 and diacylglycerol are regularly used to impart either negative or a positive surface charge. Since positively charged and negatively charged liposomes are all the more quickly taken-up by the reticulo-endothelial framework when compared with neutral liposomes, charge inducers are utilized to conquer this issue. Additionally, they end up being valuable in reducing aggregation as neutral liposomes demonstrate higher tendency to experience aggregation.

Preparation of liposomes:

There are mainly two mechanisms of vesicle formation.

The budding theory.

 Stress induced hydration of phospholipids.

 Organization in to lamellar exhibits.

 Results in to budding of lipid bilayer leading to downsizing. (Figure 4)

The bilayers phospholipids theory.

Liposomes (lipid vesicles) are shaped when thin lipid films or lipid cakes are hydrated and stacks of fluid crystalline bilayers become liquid and swell. The hydrated lipid sheets disconnect during agitation and self-close structure to form large multilamellar vesicles (LMV).

Figure 4: The budding theory

Figure 5: Mechanism of vesicle formation¹³.

When these particles have framed, decreasing the size of the molecule requires energy contribution in the form of sonic energy (sonication) or mechanical energy (expulsion). (Figure 5) In the mid-1980s the nature of lipids of a few providers could differ significantly; both in quantitative and subjective terms. These days, a couple of providers furnish the worldwide market with great items. Quality is guaranteed by improved refinement scheme, the presentation of validated analytical methods and a superior knowledge into lipid deggardation mechanisms. Yet at the same time choice of appropriate lipid relies upon not many variables.

Methods of liposomepreparation^11-14

Method of liposome preparation and drug loading:

Since the mid-1970s a large number of medications, including anti-tumor and antimicrobial agents, chelating agents, peptide hormones, chemicals, different proteins, immunizations and genetic materials, have been fused into the aqueous or lipid phases of liposomes of different sizes, compositions and different qualities by an ever-expanding number of methods. Liposomes have advanced from minor exploratory apparatuses of research to industrially fabricated items for clinical and veterinary use. This achievement relies upon advanced technique to get proficient medication entrapment and increased stability of the product. The conventional method and the advanced techniques dependent on this technique are discussed as follows;

The following methods are utilized for the preparation of liposome:

 Passive loading methods

 Active loading method.

Passive loading method incorporate three unique methods:

 Mechanical dispersion technique.

 Solvent dispersion technique.

 Detergent removal strategy (evacuation of non-encapsulated material).

Detergent can be removed by

 Dialysis method

 Column chromatography method

 Bio-globules technique

Mechanical dispersion method:

The following up next are kinds of mechanical dispersion method:

 Sonication.

 French pressure cell: expulsion.

 Freeze-thawed liposomes.

 Lipid film hydration by hand shaking, non-hand shaking or freeze drying.

 Micro-emulsification.

 Membrane expulsion.

 Dried reconstituted vesicles.

Solvent injection or dispersion method:

 Ethanol injection method

 Ether injection method

 Double emulsion vesicles method

 Reverse phase evaporation method

 Stable plurilameller vesicles method

Miscellaneous techniques:

 Hydration of lipids in present of solvent

 High pressure extrusion

 Slow swelling in Non-electrolyte solution

 Removal of Chemotropic ion

Sonication:

Sonication is maybe the most broadly utilized technique for the preparation of SUV. Here, MLVs are sonicated either with a bath type sonicator or a probesonicator under a passive atmosphere. The primary disadvantages of this method are low internal volume/encapsulation efficacy, conceivable degradation of phospholipids and compounds to be encapsulated, disposal of large particles, metal contamination from probe tip, and presence of MLV alongside SUV.

Probe sonication:

The tip of a sonicator is legitimately immersed into the liposome dispersion. The energy contribution to lipid dispersion is high in this method. The coupling of energy at the tip brings about nearby hotness; in this way, the vessel must be immersed into a water/ice bath. All through the sonication up to 1 h, over 5% of the lipids can be de-esterified. Likewise, with the probeSonicatortitanium will slough off and contaminate the solution.

Bath sonication:

The liposome dispersion in a chamber is set into a bathsonicator. Controlling the temperature of the lipid dispersion is generally simpler in this method, difference to sonication by dispersal straightforwardly utilizing the tip. The material being sonicated can be ensured in a sterile vessel, dissimilar the probe units, or under an inactive atmosphere14.

French pressure cell: extrusion:

French pressure cell includes the extrusion of MLV through a little hole. A significant component of the French press vesicle technique is that the proteins don't appear to be altogether pretentious during the procedure as they are in sonication. A fascinating remark is that French press vesicle seems to review captured solutes altogether longer than SUVs do, created by sonication or detergent removal. The technique includes delicate treatment of unstable materials. The strategy has advantages over sonication technique. The subsequent liposomes are preferably bigger over sonicated SUVs. The disadvantages of the technique are that the high temperature is hard to attain, and the working volumes are nearly small (around 50mL as the most extreme).

Freeze-thawed liposomes:

SUVs are quickly frozen and thawed gradually. The fleeting sonication dispersesaggregated materials to LUV. The formation of unilamellar vesicles is because of the combination of SUV all through the procedures of freezing and thawing. This type of synthesis is strongly restrained by expanding the phospholipid concentration and by expanding the ionic quality of the medium. The encapsulation efficacies from 20% to 30% were obtained.

Solvent dispersion method:

Ether injection (solventvaporization):

A solution of lipids dissolved in diethyl ether or ether-methanol blend is progressively injected to an aqueous solution of the material to be encapsulated at 55°C to 65°C or under reduced pressure. The subsequent evacuation of ether under vacuum leads to the production of liposomes. The main disadvantages of the system are that the population is heterogeneous (70 to 200nm) and the exposure of compounds to be encapsulated to organic solvents at high temperature.

Ethanol injection:

A lipid solution of ethanol is quickly injected to a huge abundance of buffer. The MLVs are at once formed. The disadvantages of the method are that the populace is heterogeneous (30 to 110 nm), liposomes are extremely dilute, the removal of all ethanol is troublesome on the grounds that it structures into azeotrope with water, and the likelihood of the various biologically active macromolecules to inactivate within the sight of even low measures of ethanol is high.

Reverse phase evaporation method:

This technique gave an advancement in liposome innovation, since it considered the first run through the planning of liposomes with a high aqueous space-to-lipid proportion and a capacity to entangle an enormous level of the fluid material displayed. Reverse phase evaporation depends on the production of inverted micelles. These inverted micelles are shaped upon sonication of a blend of a buffered aqueous phase, which contains the water-soluble particles to be encapsulated into the liposomes and an organic phase wherein the amphiphilic atoms are solubilized. The moderate disposal of the organic solventleads to the transformation of these inverted micelles into viscous state and gel structure. At a basic point right now, gel state breakdown, and a portion of the inverted micelles were disturbed. The overabundance of phospholipids in the environment gives to the arrangement of a total bilayer around the leftover micelles, which brings about the formation of liposomes. Liposomes made by reverse phase evaporation technique can be produced using various lipid formulations and have aqueous volume-to-lipid proportions that are multiple times higher than hand-shaken liposomes or multilamellar liposomes. Briefly, first, the water-in-oil emulsion is shaped by sonication of a two-stage framework, containing phospholipids in organic solvent, for example, isopropyl ether or diethyl ether or a mixture of isopropyl ether and chloroform with aqueous buffer. The organic solvents are withdrawn under reduced pressure, bringing about the formation of a thick gel. The liposomes are shaped when residual solvent is detached during continued rotary evaporation under decreased pressure. With this technique, high encapsulation effectiveness up to 65% can be acquired in a mechanism of low ionic quality. Example 0.01 M NaCl. The technique has been utilized to encapsulate small, large, and macromolecules. The fundamental disadvantage of the method is the contact of the materials to be encapsulated to organic solvents and to brief times of sonication. These conditions may perhaps bring about the breakage of DNA strands or the denaturation of certain proteins. Modified reverse phase evaporation method was exhibited by Handa et al., and the principle advantage of the method is that the liposomes had high encapsulation efficacy (about 80%).

Detergent removal method (evacuation of non-encapsulated material)

Dialysis:

The detergent at their critical micelle concentrations (CMC) have been utilized to solubilize lipids. As the detergent is segregated, the micelles become progressively better-off in phospholipid and finally join to shape LUVs. The detergents were expelled by dialysis. A commercial gadget called LipoPrep (Diachema AG, Switzerland), which is a version of dialysis framework, is possible for the disposal of detergents. The dialysis can be acted in dialysis bagsengrossed in huge detergent free buffers (equilibrium dialysis) 15.

REVIEW OF LITERATURE^1-8

Writing review for Lipid based drug delivery system

1. Chime and Onyishi et al, 2013 showed that the use of lipids as vehicle for the delivery of medications has revolutionarizeddrug delivery with some old medications with intense symptoms being safe for use. Some anti-inflammatory drugs for instance, indomethacin, (SLM, SEFs) have demonstrated that indomethacin lipid formulations could be utilized with minimal gastro-intestinal irritation1.

2. Saroj et al, 2012 considered Lipid-based delivery system are an acknowledged, demonstrated, economically feasible technique to formulate pharmaceuticals, for topical, oral, pulmonary or parenteral conveyance. Lipid based plans can be custom-made to meet a wide scope of product necessities directed by disease sign, route of administration, cost thought product strength, toxicity, and efficacy. They were for the most part center around lipid details to be specific microemulsions, self-emulsifying delivery system, nanoemulsions, pickering emulsions, liposomes, phytosomes, transfersomes, ethosomes, archaesomes, vesosomes, lipid microparticles and lipid nanoparticles and their distinctive applications in pharmaceutical medication delivery 2.

3. Gonnade et al, 2014 presume that the Lipid has brilliant future because of their huge application in the distinctive field like pharmaceutical and cosmaceutical. Though, some the obstacles are their like poor stability, poor aqueous dissolvability, polymorphism. Every one of these issues are significant parameters for the detailing in the lipid-based drug delivery system (LBDDS). Right now, lipid is for the most part use as the major excipients and it is important to know all the data about the lipids also, it is the advantages of the above study3.

Literature survey for liposome^9-12

1. Gupta et al, 2010 arranged liposomes, niosomes and phytovesicles of pure curcumin and fused into carbopol gel to make possible for topical application on skin. They found that these vesicles gave improved antiaging, antioxidant and anti-wrinkle effect 20.

2. Rathore et al, 2010 arranged miconazole incorporated distinctive novel transporters, for example, liposomes, ethosomes and analyzed there in vitro skin penetration studies with plane ointment utilizing skin model. In vitro skin permeation study results indicated that the consistent state transitions of medication were higher in case of ethosomal suspension incorporated ointment when contrasted with liposomal ointment. Consequently, inferred that ethosomes shows better skin saturation when contrasted with liposomes 21.

3. Takahashi et al, 2009 detailed that liposomes encapsulating Aloe vera leaf gel extract essentially improve expansion and collagen synthesis in human skin cell lines. Additionally, demonstrated that the bioavailability and skin care properties of Aloe Vera leaf gel concentrate will be fundamentally improved by liposome encapsulation, and the present liposomal Aloe Vera leaf gel extract should have an incredible potential as aeffective healthy skin formulation 22.

4. Caddeoa, 2008 explored the chance of improving the efficacy of resveratrol, a polyphenol with strong antioxidant and free-radical scavenging properties, on cell multiplication and photoprotection by liposomal incorporation. Liposomes prevented the cytotoxicity of resveratrol at high concentrations, even at 100μm, staying away from its immediate and massive intracellular distribution, and increased the capacity of resveratrol to stimulate the expansion of the cells and their capacity to get by under pressure conditions brought about by UV-B light 23.

5. Sinico et al, 2008 announced the impact of liposomal incorporation on both the stability and the in vitro (Trans) dermal delivery of verbascoside was evaluated. Results demonstrated that liposomes advanced medication aggregation into the stratum corneum however they didn't offer ascent to any significant transdermal verbascoside conveyance. At long last, results acquired from a 1, 1-diphenyl-2-pierylhydrazyl (DPPH) radical test showed that liposomes didn't interfere with the radical scavenging movement of verbascoside 24.

6. Golmohammadzadeh et al, 2007 had played out the assurance of SPF and moisturizing impacts of liposomal and conventional formualtions Octyl Methoxycinnamte (OMC) as a sunscreen. The consequences of study indicated that Multilamellar liposomes prepared by fusion method is a decent vehicle for OMC as a sunscreen since it gives provides SPF and increase the moisture content of the skin 25.

7. El-Samaligy et al, 2006 arranged silymarin encapsulated hybrid liposome which shows successful planning with productive encapsulation of silymarin. Consolidation of silymarin into liposomal dosage form given buccally can improve its bioavailability. Right now, improve the bioavailability of silymarin through its consolidation in a stable liposomal buccal dose structure, utilizing commercially accessible soybean lecithin 26.

8. Hung, 2006 fused Resveratrol, the primary active polyphenol in red wine, into different combinations of emulsions and liposomes to look at its physicochemical attributes and cardiovascular protection and reasoned that encapsulation by the emulsion-liposome mixes is a strong method to improve the protection and therapeutic advantages of resveratrol 27.

9. Betz et al, 2005 had done in vivo examination of different liposome definitions for cosmetic applications and revealed that liposomes and liposome formulations have been implied for skin moisturization, because of the potential occlusive impact of the phospholipid film deposited on the skin surface. So as to expand the skin water content altogether, egg phospholipids are recommended to be utilized for the preparation of the topical formulation 28.

10. Lee et al, 2005 showed that cholesterol in liposomes incredibly increases the consolidation efficacy of retinol and the stability of incorporated retinol 29.

11. Li et al, 2005 prepared liposome-encapsulated curcumin and studied in vitro and in vivo impacts on proliferation, apoptosis, and angiogenesis. The activity of liposomal curcumin was equivalent to or better than that of free curcumin at equimolar concentrations. In vivo, curcumin suppressed pancreatic carcinoma development in murine xenograft models and inhibited tumor angiogenesis 30.

12. Lee et al, 2003 studied the impact of edge activators on the development and transfection efficiency of ultradeformable liposomes (UL) and proclaimed that following topical application onto mice, DNA complexed with UL containing either sodium cholate or sodium deoxycholate indicated significant transdermal absorption. Remarkably, DNA complexed with Tween 80-based UL didn't appear in vivo transdermal ingestion.

13. Maghraby et al, 2000 said that incorporation of surfactants sodium cholate or Span 80 into Phosphatidylcholine liposomes was even better than incorporation of the penetration enhancer, oleic acid, for the skin delivery of the model lipophilic medication oestradiol. For ideal impacts, the components should be as vesicles. The general outcomes show that mechanism of penetration enhancing of liposome components isn't the main or to be sure the principle factor operating.

Literature survey for Cow's Ghee as an excipient^13-14.

1. G Y Sarwankumar et al. prepared solid lipid nanoparticles of poorly soluble drug (clozapine) were prepared by utilizing various lipids including Buffalo's ghee with various surfactants for the proportion 1:1 Clozapine SLNs were set up by hot homogenization method followed by ultrasonication and its molecule size, zeta potential, morphology, entrapment efficacy and in-vitro drug release were examined. Clozapine was effectively loaded in Ghee with entrapment effectiveness of Clozapine running from 99.15 to 99.80%.

2. A Mahakalkar et al. observed the utilizations and constraint of Cow's ghee in the treatment of different diseases. They enlist the ayurvedic properties and medicinal values of Ghee. Its flexibility as a pharmaceutical aid was altogether examined. They have referenced that Cow's ghee is utilized as a transporter for herbs and bhasmas as a result of its incomparable penetrating characteristics and along this ability to transport these substances profound into the tissues.

REFERENCES:

1. Chime SA, Onyishi IV. Review on Lipid-based drug delivery systems (LDDS): Recent advances and applications of lipids in drug delivery. African Journal of Pharmacy and Pharmacology. 2013; 33(3): 1-26.

2. Saroj S, Baby DA, SabithaM. Current trends in lipid-based delivery systems and its applications in drug delivery. Asian J Pharm Clin Res., 2012; 5(3): 4-9.

3. Yogita R. Gonnade, KN, Ambatkar A. Review on Lipid: an emerging platform for lipid-based drug delivery system. wjpps 2012; 3(4): 572-589.

4. Chauhan T, Arora S. Bharat Parashar and Abhishek Chandel, Liposome Drug Delivery: A Review. ijpcs., 2012; 1(3): 4-12.

5. Sen R, Kumar SS, Satpathy S. Liposome as drug delivery system: A brief review. Int. J. Res. Pharm. Sci., 2014; 5(4):309-321.

6. Sipai AM, Yadav VY, Prasanth VV. Liposome: An Overview. JPSI. 2012;4(7):13-21.

7. Olga P, Jana S, Zoran K, Vesna R. An Overview: Methods for Preparation and Characterization of Liposomes as Drug Delivery Systems. Int. J. Pharm. Phytopharmacol. Res. 2013;3(2):1-8.

8. Laouini, AC, Fessi H. Preparation, Characterization and Applications of Liposomes: State of the Art. Journal of Colloid Science and Biotechnology 2012;1(4):147–168.

9. Tripathi G, Chaurasiya K and Katare P. Liposomal current status, evaluation and recent advances. Int J Curr Pharm Res, 2010;5(3):4-14.

10. KumarA, Reddy GV, Maheswari J. Liposome: a novel advancement in drug delivery. IJPPDR. 2011;1(1):33-39.

11. Vladimir P. Torchilin. Recent Advances with Liposomes as Pharmaceutical Carriers. Nature reviews drug discovery. 2005:4(2)145-160.

12. Mahakalkar A, Kashyap P, BawankarR. The Versatility of Cow Ghee-An Ayurveda Perspective. American Journal of Drug Delivery and Therapeutics. 2014;1(1): 028-034

13. Thulasiramaraju TV, Sudhakar AM, Arunachalam A, Prathap M, Srikanth S, Sivaiah P. Liposomes: a novel drug delivery system. International Journal of Biopharmaceutics. 2012; 3(1): 5-16.

14. Kaur L, Kaur P and Khan MU. liposome as a drug carrier – a review. IJRPC. 2013,3(1):2231-2781.

Received on 04.05.2020 Modified on 13.06.2020

Res. J. Pharma. Dosage Forms and Tech.2020; 12(4):285-294.

DOI: 10.5958/0975-4377.2020.00047.6

Type	Composition	Characteristics
Conventional liposomes (CL)	Neutral phospholipids and cholesterol	Subject to coated-pit endocytosis; contents ultimately delivered to lysosomes, if they do not diffuse from endosome; useful for RES targeting; short circulation half -life; dose dependent PK
pH-sensitive liposomes	PE or DOPE with either CHEMS or OA	Subject to coated-pit endocytosis; at low pH, fuse with cell or endosome membranes and release their contents in cytoplasm; suitable for intracellular delivery of weak bases and macromolecules.
Charged Liposomes	Generally, SA/ODA for positive charge; DCP for negative charge	Possibly fuse with cell or endosome membranes; suitable for delivery of DNA, RNA, etc; structurally unstable; toxic at high doses
Long- Circulating Liposomes (LCL)	neutral high Tc lipids, Chol, plus 5-10%of PEG-DSPE, GM1 orHPI	Hydrophilic surface coating; low opsonization and thus low rate of uptake by RES; long circulation half- life (~ 40 hr); doseindependent PK.
Immunoliposomes	CL or LCL with attached antibody or recognition sequence	Subject to receptor-mediated endocytosis; cell specific binding (targeting); can releasecontents extracellularly near the target tissue and drugs may diffuse through plasma membranes to produce theirEffects.

1.3 Classifications7-10