Polysorbate hydrophilic-lipophilic balance

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]. 

Tween 80 (also known as At-Plus 109 and Polysorbate 80) is a polyoxyethylene sorbitan monooleate and was obtained from Atlas Chemical Industries, Inc. This nonionic surfactant has an HLB (hydrophile-lipophile balance) of 15.0 and is used as an emulsifier, solubilizer, and dispersant. It was used without further purification at the 0.1% (w/v) level in partitioning and greenhouse herbicidal evaluations as described below. 

Tween-20 (Polysorbate 20) from Fluka GmbH, Switzerland, was used as emulsifier in the watery continuous phase. Tween-20 with HLB (Hydrophilic-Lipophilic Balance) of 16.7 is well soluble in watery phases thus stabilizing oil drops in water and was applied both in simple and multiple emulsions. The molecular sum formula is C58H114026 and the CMC is ca. 4.9 x 10 M or 60 mg/1 (data sheet of manufacturer) in water. 

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