The concept of targeted drug delivery is designed for attempting to concentrate the drug in the tissues of interest while reducing the relative concentration of the medication in the remaining tissues. As a result, drug is localised on the targeted site. Hence, surrounding tissues are not affected by the drug. In addition, loss of drug does not happen due to localization of drug, leading to get maximum efficacy of the medication. Different carriers have been used for targeting of drug, such as immunoglobulin, serum proteins, synthetic polymers, liposome, microspheres, erythrocytes and niosomes¹. Niosomes are one of the best among these carriers. Structurally, Niosomes are similar to liposomes and also are equiactive in drug delivery potential but high chemical stability and economy makes Niosomes superior than liposomes. Both consist of bi-layer, which is made up of non-ionic surfactant in the case of Niosomes and phospholipids in case of liposomes.

Niosomes are microscopic lamellar structures of size range between 10 to 1000 nm and consists of biodegradable, non-immunogenic and biocompatible surfactants². Steroids are important components of the cell membrane and their presence in membrane affect the bi-layer fluidity and permeability³. Cholesterol which is a steroid derivative and used in formulation of niosomes but may not show any role in the formation of bi-layer. Here cholesterol affect properties of niosomes like membrane permeability, Rigidity, encapsulation efficiency, ease of rehydration of freeze dried Niosomes and their toxicity. It prevent the vesicle aggregation by the inclusion of molecules which can stabilize the system against the formation of aggregates by electrostatics forces or repulsive steric that leads to the transition from the gel to liquid phase in Niosomes system. Hence the Niosomes becomes leaky³.

1.2 Advantages of Niosomes⁴

· The application of vesicular (lipid vesicles and non-ionic surfactant vesicles) systems in cosmetics and for therapeutic purpose may offer several advantages: - The vesicle suspension is water–based vehicle

· This offers high patient compliance in comparison with oily dosage forms. They possess an infrastructure consisting of hydrophilic, amphiphilic and lipophilic moieties together and as a result can accommodate drug molecules with a wide range of solubilities.

· The characteristics of the vesicle formulation are variable and controllable. Altering vesicle composition, size, lamellarity, tapped volume, surface charge and concentration can control the vesicle characteristics.

· The vesicles may act as a depot, releasing the drug in a controlled manner. Other advantages of Niosomes include they are osmotically active and stable, as well as they increase the stability of entrapped drug.

· Handling and storage of surfactants requires no special conditions

· They improve oral bioavailability of poorly absorbed drugs and enhance skin penetration of drugs. They can be made to reach the site of action by oral, parenteral as well as topical routes.

· They are osmotically active, stable and also increase the stability of entrapped drug. Oral, parenteral as well as topical routes can be adopted for their administration.

· By improving oral bioavailability of poorly absorbed drugs, by delaying clearance from the circulation and by protecting the drug from biological environment they improve the therapeutic performance of the drug molecules

1.3 Disadvantages of Niosomes^1-2

· Steroids are important components of the cell membrane and their presence in membrane affect the bi-layer fluidity and permeability.

· Cholesterol which is a steroid derivative and used in formulation of niosomes but may not show any role in the formation of bi-layer.

· Here cholesterol affect properties of niosomes like membrane permeability, Rigidity, encapsulation efficiency, ease of rehydration of freeze dried niosomes and their toxicity.

· It prevent the vesicle aggregation by the inclusion of molecules which can stabilize the system against the formation of aggregates by electrostatics forces or repulsive

· Steric that leads to the transition from the gel to liquid phase in niosomes system. Hence the Niosomes becomes leaky.

2.3. Micro-fluidization

Micro fluidization is a recent technique used to prepare uni-lamellar vesicles of defined size distribution. This method is based on submerged jet principle in which two fluidized streams interact at ultra high velocities, in precisely defined micro channels within the interaction chamber. The impingement of thin liquid sheet along a common front is arranged such that the energy supplied to the system remains within the area of Niosomes formation. The result is a greater uniformity, smaller size and better reproducibility of Niosomes formed. ^5-6

Fig.no.1 Niosome structure formed by non-ionic surfactant

2.4. Reverse Phase Evaporation Technique (REV)

Cholesterol and surfactant (1:1) are dissolved in a mixture of ether and chloroform. An aqueous phase containing drug is added to this and the resulting two phases are Sonicated at 4-5°C. The clear gel formed is further Sonicated after the addition of a small amount of phosphate buffered saline (PBS). The organic phase is removed at 40°C under low pressure. The resulting viscous Niosomes suspension is diluted with PBS and heated on a water bath at 60°C for 10 min to yield Niosomes. Raja Naresh et al have reported the preparation of Diclofenac Sodium Niosomes using Tween 85 by this method.^5-6

2.5. Ether injection method

This method provides a means of making Niosomes by first prepared a solution of non-ionic surfactant mixture than slowly introducing a solution of surfactant dissolved in diethyl ether into warm water maintained at 60°C. The surfactant mixture in ether is injected through 14-gauge needle into an aqueous solution of material. Single layered vesicles are formed by vaporization of ether. the diameter of the vesicle range from 50 to 1000 nm. The small amount of ether is often still present in the vesicle suspension and is often difficult to remove that is the major problem of this method.^5-6

2.6 Trans membrane pH gradient (inside acidic) Drug Uptake Process (remote Loading) Surfactant and cholesterol are dissolved in chloroform. The solvent is then evaporated under reduced pressure to get a thin film on the wall of the round bottom flask. The film is hydrated with citric acid (pH 4.0) by vortex mixing. The multi-lamellar vesicles are frozen and thawed 3 times and later Sonicated. To this Niosomal suspension, aqueous solution containing 10 mg/ml of drug is added and vortexed. The pH of the sample is then raised to 7.0-7.2 with 1M disodium phosphate. This mixture is later heated at 60°C for 10 minutes to give Niosomes.^5-6

2.7 The Bubble Method

It is novel technique for the one step preparation of liposomes and Niosomes without the use of organic solvents. The bubbling unit consists of round-bottomed flask with three necks positioned in water bath to control the temperature. Water-cooled reflux and thermometer is positioned in the first and second neck and nitrogen supply through the third neck. Cholesterol and surfactant are dispersed together in this buffer (pH 7.4) at 70°C, the dispersion mixed for 15 seconds with high shear homogenizer and immediately afterwards “bubbled” at 70°C using nitrogen gas.^5-6

2.8 Sonication

A typical method of production of the vesicles is by sonication of solution as described by Cable In this method an aliquot of drug solution in buffer is added to the surfactant/choleste mixture in a 10-ml glass vial. The mixture is probe sonicated at 60°C for 3 minutes using a sonicator with a titanium probe to yield niosomes.⁷

3.1 Formation of niosomes from proniosomes

Proniosomes are dry formulations of surfactant coated carrier and these are rehydrated by gentle agitation in hot water. Proniosomes are prepared by spraying surfactant in organic solvent onto sorbitol powder and then evaporating the solvent. The sorbitol acts as a carrier which is soluble in organic solvent so it is needed to repeat the process until the desired surfactant loading has been achieved. The surfactant coating on the carrier is very thin and hydration of this coating allows the formation of mult-lamellar vesicles. The resulting niosomes are very similar to those produced by conventional methods and size distribution is more uniform. This method is suitable for formulation of hydrophobic drugs in a lipid suspension by minimizing problems of niosomes physical stability such as aggregation, fusion and leaking and provides additional convenience in transportation, distribution, storage and dosing.⁷

Fig.no.2 Formation of Proniosome to Niosome.

3.2 Separation of Unentrapped Drug ^8,10

The removal of unentrapped solute from the vesicles can be accomplished by various techniques, which include

 Dialysis

The aqueous Niosomal dispersion is dialyzed in a dialysis tubing against phosphate buffer or normal saline or glucose solution.

 Gel Filtration

The unentrapped drug is removed by gel filtration of Niosomal dispersion through a Sephadex-G-50 column and elution with phosphate buffered saline or normal saline.

 Centrifugation

The Niosomal suspension is centrifuged and the supernatant is separated. The pellet is washed and then resuspended to obtain a Niosomal suspension free from un-entrapped drug.

4.1Comparison of Niosomes and Liposomes⁹

Niosomes are now widely studied as an alternative to liposomes, which exhibit certain disadvantages such as –they are expensive, their ingredients like phospholipids are chemically unstable because of their predisposition to oxidative degradation, they require special storage and handling and purity of natural phospholipids is variable. Niosomes are prepared from uncharged single-chain surfactant and cholesterol whereas liposomes are prepared from Doublechain phospholipids (neutral or charged). Niosomes behave in-vivo like liposomes, prolonging the circulation of entrapped drug and altering its organ distribution and metabolic stability. Encapsulation of various anti neoplastic agents in these carrier vesicles has been shown to decrease drug induced toxic side effects, while maintaining, or in some instances, increasing the anti-tumor efficacy. Such vesicular drug carrier systems alter the plasma clearance kinetics, tissue distribution, metabolism and cellular interaction of the drug. They can be expected to target the drug to its desired site of action and/or to control its release.

4.2 Characterization and factors affecting formulation of Niosomes^9-10

 Nature of surfactants

A surfactant used for preparation of niosomes must have a hydrophilic head and hydrophobic tail. The hydrophobic tail may consist of one or two alkyl or perfluoro-alkyl groups or in some cases a single steroidal group. The ether type surfactants with single chain alkyl as hydrophobic tail is more toxic than corresponding di-alkyl ether chain. The ester type surfactants are chemically less stable than ether type surfactants and the former is less toxic than the latter due to ester-linked surfactant degraded by esterases to triglycerides and fatty acid in vivo. The surfactants with alkyl chain length from C12-C18 are suitable for preparation of noisome.

Physical properties of Niosomes ¹⁰

Particle size

The particle size of Niosomes was measured by dynamic light scattering (DLS) apparatus (NICOMP 380 ZLS, Particle Sizing Systems, Santa Barbara, CA). The dispersions were diluted to about 100 times with Dulbecco’s PBS. The time-dependent correlation function on the scattered light intensity was measured at a scattering angle of 90 ͦ and wavelength at 535 nm.

Morphology ¹⁰

The dispersion of Niosomes was rapidly frozen in liquid propane using cryo-preparation apparatus (Leica EM CPC, Leica Co., Vienna, Austria). The frozen sample was fractured in freeze-replica-making apparatus (FR-7000A, Hitashi Science Co., Tokyo, Japan) at – 150^oC. The fracture surface was replicated by evaporating platinum at an angle of 45^oC and followed by carbon to strengthen the replica. It was placed on a 150 mesh copper grid after washing with acetone and water. The vesicles were observed under a transmission electron microscope (JEM-1200EX, JEOL Co.)

Fig.no.3 Microscopic size of niosome

5.1 Evaluation ^{10, 11, 12}

 Entrapment efficiency

After preparing Niosomal dispersion, un-entrapped drug is separated by dialysis centrifugation and gel filtration. The drug remain entrapped in Niosomes is determined by complete vesicle disruption using 50% n-propanol or 0.1% Triton X-100 and analyzed resultant solution by appropriate assay method using following equation.

 Particle size analysis^10-12

Particle size analysis was done by scanning electronic microscopy (SEM) using JEOL JSM-T330A scanning microscope brass stab. The stabs were placed briefly in a drier and then coated with gold in an ion sputter. Pictures of Niosomes were taken by random scanning of the stub and count. The diameter is about 30 Niosomes was measured from the photomicrographs of each batch. Finally, average mean diameters were taken into consideration.

 In-vitro release study ^10-12

Human cadaver skin (HCS) was obtained from ventral part of forearm of 35 years old male corpse and was stored at 4°C. HCS membrane was spread and punches it at approximately 3 cm2 area. Trimmed away the excess fat and sliced to 500 um thickness using a Daw’s derma tone. These slices were hydrated in pH 7.4 PBS for 24 hrs prior to use. The HCS were attached to Khesary cell (K.C filled with 100 ml of PBS) and add 10 mg Niosomal suspension on it. Finally, cell was immersed into the receptor compartment. The dermal surface was just flush to the surface of permeation fluid (PBS), which was maintain at 37°C ,0.50°C and stirred magnetically at 50 r.p.m., aliquots were withdraw and replaced with the same volume of fresh buffer, at every sampling points and analyzed by U. V. Spectrophotometer method at 294 nm.

 Stability study ^10-12

All Niosomal formulations were subjected to stability studies by storering at 4°C, 25°C and 37°C in thermostatic oven for the period of three months. After one month, drug content of all the formulations were checked by method discussed previously in entrapped efficiency parameter. In-vitro release studies of selected formulations were also carried out.

6.1 Application of Niosomes

 Niosomes in the treatment of Leishmaniasis ^13-14

Leishmaniasis is a disease in which parasite invades cells of liver and spleen. The commonly prescribed drugs in the treatment of Leishmaniasis are antimonials, which are related to arsenic and at high concentration they damage the heart, liver and kidney. The administration of these drugs in the form of Niosomes can prevent organ damage.

 Niosomes in Oncology¹⁴

Drug delivery to the tumor can be more effective for Methotrexate and Doxorubicin when administered in the form of Niosomes. Doxorubicin is an anthracyclic antibiotic with broad spectrum anti-neoplastic activity, shows a dose dependant cardiomyopathy and myelosuppression. The vesicles with polyoxyethylene surface were rapidly taken up by the liver and accumulated to a lesser extent in tumor. Intravenous administration of Methotrexate entrapped in Niosomes to S-180 tumor bearing mice resulted in total regression of tumor and also higher plasma level and slower elimination of the drug.

 Niosomes as Immunological Adjuvant^15-16

Niosomes have been used for studying the nature of the immune response provoked by antigens. Brewer and Alexander have reported Niosomes as potent adjuvant in terms of immunological selectivity, low toxicity and stability by comparing the enhanced antibody production in response to bovine serum albumin with Freund’s complete adjuvant. Moser et al carried out study on Niosomal hemoglobin for its compatibility and interaction with blood. The study mainly involves the agglutination phenomenon with ABO blood group components as plasma extenders and erythrocyte phenotypes. Vyas SP et al carried studies on non – invasive topical genetic immunization against Hepatitis B in the form of Niosomes.

 Niosomes for Oral Drug Delivery¹⁷

Yoshida et al investigated oral delivery of peptide drugs such as 9-desglycinamide–8-arginine vasopressin entrapped in polyoxyethylene-3 or 7-stearyl ether Niosomes in an in vitro intestinal loop model which results in significant increased stability of peptide drugs. The oral bioavailability of celecoxib and griseofulvin can be enhanced by formulating in the form proniosomes and niosomes respectively. A developed Insulin niosomes as sustained release oral dosage form using Brij as non ionic surfactant by film hydration method.

 Niosomes for Transdermal Delivery¹⁷

Slow penetration rate of drug through skin is the major drawback of transdermal drug delivery systems. An increase in the penetration rate has been achieved by transdermal delivery of drug incorporated in the form of niosomes. Jayaraman et al has studied the topical delivery of erythromycin from various formulations including niosomes on hairless mouse. Balakrishnan P et al studied enhanced skin delivery and bioavailability of minoxidil niosomes in hair loss treatment prepared by using Brij/Span with cholesterol using film hydration method.

 Niosomes as Diagnostic Agents ^18-19

Niosomes can also be used for diagnostic purposes. Korkmaz et al formulated DTPA carrying niosomes (hexadecyl triglycerol ether: cholesterol: DTPA) to study the in vitro release, radiolabelling, in vivo distribution and to perform scintigraphic imaging studies. They found that niosomes can act as good carrier for radiopharmaceuticals and site specific vesicle for spleen and liver imaging.

 Niosomes as Ophthalmic Carriers^20-21

Acetazolamide in the form of niosomes can improve the low corneal penetration and bioavailability characteristics in rabbit. Abdelkader H successfully developed and characterized naltrexone HCl niosomes using reverse phase evaporation and thin film hydration method as ocular delivery system.

Type of Non-ionic surfactant used in niosomes preparation with example^22-24

Table.no.1

S.no	Type of Non-ionic surfactant	Examples
1	Fatty alcohol	Cetyl alcohol, Steryl alcohol, Cetosteryl alcohol, oleyl alcohol
2	Ethers	Decyl glucoside, Lauryl glucoside, Octyl glucoside, Triton X-100, Nonoxynol-9
3	Esters	Glyceryl laurate, Polysorbates, Spans
4	Block copolymers	Poloxamers

6.2 CONCLUSION:

Many years of research on vesicular system, Niosome are one of the unique vesicles in witch hydrophilic, lipophilic and amphiphilic types of drugs can be incorporated they produced the specific effect on the targeted drug delivery. Niosomes are overcomes the drawback of liposomes like leakage, short life span, aggregation. So one of the best vesicular system in novel drug delivery. Niosomes giving a good results in transdermal drug delivery system, oral drug delivery system, immune system.

7. REFERENCE:

1. Allen TM: Liposomal drug formulations: Rationale for development and what we can expect for the future. Drugs, 1998, (56), 747-756.

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3. Verma S, Singh SK, Navneet S, Mathur P, Valecha V: Nanoparticle vesicular systems: a versatile tool for drug delivery. J Chem Pharm Res, 2010.P.496-509.

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6. Maver LD, Bally MB, Hope MJ, Cullis PR, Biochem. Biophys. Acta. 816, 1985, pp. 294-302

7. Blazek-Walsh AI, Rhodes DG, SEM imaging predicts quality of niosomes from maltodextrin-based proniosomes, Pharm. Res. 18, 2001, pp. 656-661.

8. Rogerson A., Cummings J., Willmott N. and Florence A.T. The distribution of doxorubicin in mice following administration in niosomes. J Pharm Pharmacol. 1988; 40(5): 337–342.

9. Blazek-Walsh AI, Rhodes DG. SEM imaging predicts quality of niosomes from maltodextrin-based proniosomes. Pharm. Res. 18:2001; 656-61.

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11. Yoshioka T, Stermberg B and Florence AT. Preparation and Properties of Vesicles (Niosomes) of Sobitan Monoesters (Span 20, 40, 60, and 80) and a Sorbitan Triester (Span 85). Int J Pharm. 1994;105:1-6.

12. Gayatri DS, Venkatesh P and Udupa N. Niosomal Sumatriptan Succinate for Nasal Administration. Int J Pharm Sci. 2000;62(6):479-481.

13. Chandraprakash KS, Udupa N, Umadevi P and Pillai GK. Ind. J. Pharm. Sci. 1992; 54 (5): 197.

14. Baillie AJ, Coombs GH and Dolan TF, Non-ionic surfactant vesicles, niosomes, as delivery system for the anti-leishmanial drug, sodium stribogluconate, J. Pharm. Pharmacol., 38, 1986, pp. 502-505

15. Conacher M, Alexanderand J, Brewer JM, Conacher M, and Alexander J, Niosomes as Immunological Adjuvants. In “Synthetic Surfactant Vesicles” (Ed. I.F. Uchegbu) International Publishers Distributors Ltd. Singapore, 2000, pp. 185-205.

16. Brewer JM and Alexander JA.. Immunology. 1992; 75 (4):570-575.

17. Akul Mehta, PharmaXChange_info - Articles – Niosomes

18. Moser P, Arvier MM, Labrude P, Vignerson C, Pharm Acta Helv. (1990) 65 (3): 82.

19. Vyas SP, Singh RP, Jain S, Mishra V, Mahor S, Singh P, Gupta PN, Rawat A, Dubey P. Int J Pharm. 2005 May 30; 296(1-2):80-6.

20. Yoshioka T, Sternberg B, Moody M and Florence AT. J. Pharm. Pharmcol. Supp. 1992; 44: 1044.

21. Nasr M. AAPS PharmSciTech. 2010 Mar; 11(1):85-9.

22. Jadon PS, Gajbhiye V, Jadon RS, Gajbhiye KR, Ganesh N. AAPS PharmSciTech. 2009;10(4):1186-92.

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Received on 09.06.2014 Modified on 21.06.2014

Asian J. Research Chem. 7(7): July 2014; Page 687-692

Name of drug	Category	Year of work
Methotrexate	Psoriasis	Azmin et al -1985,Chandraprakash etal-1992,1993,Udupa et al- 1993 Lakshmi et al -2007
5,6- carboxy fluorescence	Diagnostic agent	Baillie et al -1985
Sodium stibogluconate	Anti-leishmaniasis	Baillie et al -1986 Carter et al -1989
Adriamycin	Anti-cancer	Rogerson et al- 1987
Doxorubicin	Anti-cancer	Rogerson et al- 1988 Cable et al -1989 Uchegbu et al -1995
Antimony	Anti-leishmaniasis	Hunter et al -1988
Hemoglobin 9-desglycinamide, 8-arginine	Oxygen carrier Peptides	Moser et al -1989 Yoshida et al -1992
Bovine serum albumin Flurbiprofen, Piroxicam	Protein Anti-inflammatory	Brewer and Alexander-1992 Reddy et al -1993
Vincristine sulphate, Diclofenac	Anti-cancer Anti-inflammatory	Parthasarthi et al -1994 Raja naresh et al -1994
Estradiol	Hormone Anti-tubercular	Hofland et al -1994 Don et al-1997 Jain et al-1995,2006 Mullaicharam et al- 2004