Niosomes

Baillie, A.J. et al.. The preparation and properties of niosomes-non-ionic surfactant vesicles, J. Pharm. Pharmacol., 37, 863, 1985. 

Palozza, P. et al.. Solubilization and stabilization of P-carotene in niosomes delivery to cultured cells, Chem. Phys. Lipids, 139, 322, 2006. 

Mention should also be made in this section of niosomes, which are nonionic surfactant vesicles that have shown promise as inexpensive and chemically stable alternatives to liposomes [67]. 

The delivery of doxorubicin to the SI80 sarcoma (tumor) in mice, using niosomes as a carrier, has been studied by Rogerson [168]. Much higher tumor drug levels were reported with niosomes prepared using the nonionic surfactant I and 50% cholesterol than with free... 

Niosomes (prepared using surfactant I and surfactant I, II, or III and 30% cholesterol) containing stibogluconate have been as effective as the corresponding liposomal drugs in the visceral leishmaniasis model. Free drug showed reduced efficacy [169],... 

A. J. Baillie, Niosomes A putative drug carrier system, in Targeting of Drugs. Anatomical and Physiological Considerations (G. Gregoriadis and G. Poste, eds.), NATO Series. Series A. Life Science, Vol. 155, Plenum Press, New York, 1988, p. 143. 

The polar character of the liposomal core makes the encapsulation of polar drug molecules possible. Amphiphilic and lipophilic molecules are solubilized within the phospholipid bilayer according to their affinity toward the phospholipids. Participation of nonionic surfactants instead of phospholipids in the bilayer formation results in Niosomes . The term sphingosomes is suggested for vesicles from sphingolipids. However, the nomenclature is not consistent, and the term liposomes is used as a general term, although vesicles would be the better choice. 

Uchegbu I, Vyas S. Non-ionic surfactant based vesicles (niosomes) in drug delivery. Int J Pharm 1998 172 33-70. 

Niosomes and Elastic Niosomes—Nonionic Surfactant Vesicles.259... 

NIOSOMES AND ELASTIC NIOSOMES—NONIONIC SURFACTANT VESICLES... 

Nonionic surfactant vesicles (niosomes) were first proposed by Handjani-Vila et al. [36] as systems to improve accumulation of the active molecule within the skin and thus benefit cosmetic products. These reports opened the way for an intensive investigation of these vesicles as carriers for skin administration of drugs [37-47],... 

In certain cases, cholesterol is required for vesicle formation. It is commonly accepted that the hydrophilic lipophilic balance (HLB) is a parameter that could indicate the vesicleforming potential of surfactants. For amphiphils such as sorbitan esters and alkyl ethers, low HLB values could predict vesicle formation [52,55]. However, niosomes were obtained from polysorbate 20 (HLB 16.7), a highly hydrophilic molecule, when cholesterol at an appropriate concentration was added to the amphiphil [44], In this case it could be assumed that a kind of amphiphilic complex with a lower HLB was responsible for the vesicle formation. An excellent review on the structure, characteristics, chemical composition, and mechanism of action of niosomes was published by Uchegbu and Vyas [41]. 

The methods for preparation of niosomes are similar and as complicated as those used for liposomes. One of the most frequently utilized techniques consists of the hydration of a mixture of the surfactant-lipid at elevated temperature followed by optional size reduction (by sonication, extrusion, homogenization, etc.) to obtain a homogeneous colloidal dispersion and separation of the unentrapped drug [36,40,41,52,55],... 

A number of works investigated the interaction between niosomes and human skin. With niosomes prepared from Ci2 alcohol polyoxyethylene ether and cholesterol, vesicular structures of about 100 nm size have been observed between the first and second layers of human corneocytes 48 h after incubation as well as in the deeper strata of the skin [37], The authors concluded that the structures visualized in the deeper regions could be vesicles reorganized from individual molecules that penetrated the skin. In another study, electron micrographs illustrated that niosomes containing surfactants and cholesterol affected only the most superficial corneocytes. Moreover, two-photon fluorescence microscopy confirmed that fluorescent probe encapsulated in niosomes was confined to the intercellular spaces within the apical stratum corneum layers [56]. 

Hofland et al. investigated the in vitro permeation behavior of estradiol from niosomes (rt-alkyl polyoxyethylenes/cholesterol) through human stratum corneum. In this study examining drug delivery from multilamellar niosomes, small unilamellar niosomes and a micellar solution, all being saturated systems containing 1.5, 1.5, and 0.75 mM estradiol, very low permeation fluxes were detected (64+17, 45 + 15, and 42 + 2 ng/cm2/h, respectively) [40]. 

Occlusion is a condition that could affect drug transport from niosomes and through the stratum corneum. Such an effect was reported for saturated estradiol niosomal formulations composed of polyoxyethylene alkyl ether surfactants and sucrose ester surfactants with cholesterol and dicetyl phosphate, for which occlusion enhanced the drug human stratum corneum transport [43]. 

More recently, Carafa et al. showed that niosomes could be obtained from polyoxyethylene sorbitan monolaurate-cholesterol in aqueous environment. These authors investigated the delivery of lidocaine HC1 and lidocaine base from vesicles through silicone membrane and nude mice skin [44]. It was found that only the charged molecule (loading pH 5.5) could be encapsulated within the vesicles ( 30%). This behavior was explained by the entrapment ability of the hydrophilic moiety within the aqueous core of the vesicles. The lipophilic unionized form of lidocaine (loading pH 8.6) remained unattached. The amount of lidocaine permeated through nude mice skin from these niosomes was similar to liposomes and only about twofold greater than from a micellar system. 

The stability of various niosomal formulations depends on factors such as preparation methods, storage temperature, the encapsulated drug, the surfactants, and additive mixture [41,52,64,65], It may be possible to stabilize niosomes by a variety of methods such as the use of membrane-spanning lipids, the interfacial polymerization of surfactant monomers in situ, addition of polymerized surfactants, cholesterol, steric and electrostatic stabilizers to the formulation [41,52]. In general, vesicle aggregation may be prevented by inclusion of... 

Skin safety of niosomes was tested in a number of studies. As an example, the toxicity of polyoxyethylene alkyl ether vesicles containing Ci2-i8 alkyl chains and 3 and 7 oxyethylene units was assessed by measuring the effect on proliferation of cultured human keratinocytes [47]. It was found that the length of either polyoxyethylene headgroup or alkyl chain had only a minor influence on keratinocyte proliferation. However, the ether surfactants were much more toxic than esters tested in this study. The concentrations of ether surfactants required to inhibit cell proliferation by 50% were 10-fold lower than for ester surfactants. Neither the HLB nor the critical micelle concentration values or cholesterol content affected keratinocyte proliferation. 

Junginger, H.E, H.E. Holland, and J.A. Bouwstra. 1991. Liposomes and niosomes Interactions with human skin. Cosmet Toiletries 106 45. 

Schreier, H., and J.A. Bouwstra. 1994. Liposomes and niosomes as topical drug carriers Dermal and transdermal drug delivery. J Control Release 30 1. 

Arunothayanun, P., et al. 2000. The effect of processing variables on the physical characteristics of non-ionic surfactant vesicles (niosomes) formed from a hexadecyl diglycerol ether. Int J Pharm 201 7. 

Uchegbu, I.F., and A.T. Florence. 1995. Non-ionic surfactant vesicles (niosomes) Physical and pharmaceutical chemistry. Adv Colloid Interface Sci 58 1. 

Uchegbu, I.F., et al. 1995. Distribution, metabolism and tumoricidal activity of doxorubicin administered in sorbitan monostearate (span-60) niosomes in the mouse. Pharm Res 12 1019. 

Yoshioka, T., B. Sternberg, and A.T. Florence. 1994. Preparation and properties of vesicles (niosomes) of sorbitan monoesters (span-20, span-40, span-60 and span-80) and a sorbitan triester (span-85). Int J Pharm 105 1. 

Aggarwal, D., A. Garg, and I.P. Kaur. 2004. Development of a topical niosomal preparation of acetazolamide Preparation and evaluation. J Pharm Pharmacol 56 1509. 

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