Introduction to Niosomes.

Introduction.

Niosomes are a novel drug delivery system that encapsulates the medication in a vesicular system made up of non ionic surfactants.
The vesicle is made up of a bilayer of non-ionic surfactants, thus the name niosomes.
Niosomes are extremely small and microscopic (on a nanometric scale).
Despite having a similar structure to liposomes, they have several advantages over them.

The vesicles may act as a depot, releasing the drug in a controlled manner.
They are osmotically active and stable, and also they increase the stability of entrapped drugs.
They improve the therapeutic performance of the drug molecules by delayed clearance from the circulation, protecting the drug from biological environment and restricting effects to target cells.
The surfactants used are biodegradable, biocompatible and nonimmunogenic.
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.
Handling and storage of surfactants requires no special conditions.
Due to the unique infrastructure consisting of hydrophilic, amphiphilic, and lipophilic moieties together, they, as a result, can accommodate drug molecules with a wide range of solubilities.
Niosomal dispersion in an aqueous phase can be emulsified in a non-aqueous phase thus regulating the delivery rate of the drug and administering a normal vesicle in an external non-aqueous phase.

Physical instability of the noisome vesicles is a major disadvantage of the niosomal drug delivery system.

Aggregation: Aggregation of the niosome vesicles can be another disadvantage to be considered.
Fusion: Fusion of the niosomal vesicles to form loose aggregates or to fuse into larger vesicles will affect the uniformity of the size of the noisome vesicles.

Leaking of entrapped drugs: leakage of the entrapped drugs from the polymer system will affect the intended properties of the niosomes.
Hydrolysis of encapsulated drugs which limit the shelf life of the dispersion.

The niosomes are classified as a function of the number of bilayers (e.g. MLV, SUV) or as a function of size. (E.g. LUV, SUV) or as a function of the method of preparation (e.g. REV, DRV).

It consists of a number of bilayer surrounding the aqueous lipid compartment separately.
The approximate size of these vesicles is 0.5-10 µm diameter.
Multilamellar vesicles are the most widely used niosomes.
These vesicles are highly suited as drug carriers for lipophilic compounds.

Niosomes of this type have a high aqueous/lipid compartment ratio, so that larger volumes of bio-active materials can be entrapped with a very economical use of membrane lipids.

These small unilamellar vesicles are mostly prepared from multilamellar vesicles by the sonication method, French press extrusion.

Niosomes are often used for target drugs to the reticulo-endothelial system.
Niosomes can also be utilized for targeting drugs to organs other than the RES. A carrier system (such as antibodies) can be attached to niosomes to target them to specific organs.
Antineoplastic Treatment:

Most antineoplastic drugs cause severe side effects. Niosomes can alter the metabolism, prolong circulation and half-life of the drug, thus decreasing the side effects of the drugs.

In diagnostic imaging with a carrier containing radio pharmaceutics.
In treatment of Leishmaniasis, where the drugs of choice are antimony derivatives which are well known for their side effects, entrapping them inside the niosomes can minimize the side effects.
Can be used to improve absorption of the poorly absorbed peptides like vasopressin.
Niosomes can be used as carriers for hemoglobin within the blood.
The niosomal vesicle is permeable to oxygen and hence can act as a carrier for hemoglobin to anemic patients.