Abstract
Oil-in-water nanoemulsions are stable systems with droplet sizes in the 20–200 nm range. The physicochemical properties of these systems may be influenced by the addition of additives. Thus, the influence of ethoxylated (EL) and acetylated lanolin (AL) addition on the droplet size, pH values, electrical conductivity and stability of nanoemulsions was investigated. Then, effect of nano-emulsions additives with EL (NE-EL) or AL (NE-AL) in hydration, oiliness and pH of the skin were evaluated. Nanoemulsion safety was evaluated through the observation of no undesirable effects after skin formulation application. Both additives caused changes in droplet size and electrical conductivity, but not in pH values. Nanoemulsions containing up to 6.0% ethoxylated lanolin and 2.0% acetylated lanolin remained stable after centrifugation tests. Higher concentrations of the additives made the nanoemulsions unstable. Stability tests showed that ethoxylated lanolin produced more stable nanoemulsions then acetylated lanolin and that the major instability phenomenon occurring in these systems is coalescence at elevated temperatures. Nanoemulsion-based lanolin derivatives increased skin hydration and oiliness and did not change cutaneous pH values. These formulations are non-toxic since they did not cause any irritation on the skin surface after nanoemulsion application, showing potential as carriers for pharmaceuticals and cosmetic applications.
Highlights
IntroductionThere has been an increased interest of the pharmaceutical and cosmetic industries in nanoemulsions due to some characteristics such as high kinetic stability, actives release efficiency on skin, excellent sensorial and esthetic aspects besides the need for less surfactant (5%–10%) reducing the possibility of skin irritation and production costs, when compared to microemulsions [1,2]
There has been an increased interest of the pharmaceutical and cosmetic industries in nanoemulsions due to some characteristics such as high kinetic stability, actives release efficiency on skin, excellent sensorial and esthetic aspects besides the need for less surfactant (5%–10%) reducing the possibility of skin irritation and production costs, when compared to microemulsions [1,2].Nanoemulsions are a class of emulsions that have droplet sizes in the 20–200 nm range and are transparent or translucent
Some researchers [1,2] have studied the stability of 15 year old nanoemulsions and concluded that they remained stable over that period, not showing alterations in droplet size
Summary
There has been an increased interest of the pharmaceutical and cosmetic industries in nanoemulsions due to some characteristics such as high kinetic stability, actives release efficiency on skin, excellent sensorial and esthetic aspects besides the need for less surfactant (5%–10%) reducing the possibility of skin irritation and production costs, when compared to microemulsions [1,2]. Nanoemulsions are a class of emulsions that have droplet sizes in the 20–200 nm range and are transparent or translucent. Some researchers [1,2] have studied the stability of 15 year old nanoemulsions and concluded that they remained stable over that period, not showing alterations in droplet size. The emulsification process can affect the droplet size, its distribution and the stability of Molecules 2016, 21, 248; doi:10.3390/molecules21030248 www.mdpi.com/journal/molecules. Lanolin (from the Latin lana, wool) is a complex substance formed by a mixture of esters from numerous combinations of long chain alcohols (C7 to C40) and fatty acids (C14 to C36) derived from the sebaceous gland of sheep and accumulated in these animals’
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