Characterizing Nanoemulsions Prepared by High Pressure Homogenization Under Various Emulsifying Conditions

Mar 1, 2010 | Contact Author | By: Ruandro Knapik and Maria Carolina Rocha dos Santos Taques, Universidade Positivo/Biological and Health Sciences Nucleus, Carlos Praes and Luciana Lima de Oliveira, O Boticário
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Title: Characterizing Nanoemulsions Prepared by High Pressure Homogenization Under Various Emulsifying Conditions
high pressure homogenizationx nanoemulsionsx nanotechnologyx emulsifiersx cosmeticsx
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Keywords: high pressure homogenization | nanoemulsions | nanotechnology | emulsifiers | cosmetics

Abstract: The present study examines formulations prepared using similar oil fractions and differing emulsifier systems and process parameters to determine why their behaviors differ. Results showed that ethoxylated emulsifier systems were the most stable, and that beyond a certain number of cycles, high pressure homogenization did not significantly improve the quality of the product.

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R Knapik, MCR dos Santos Taques, C Praes and LL de Oliveira, Characterizing nanoemulsions prepared by high pressure homogenization under various emulsifying conditions, Cosm & Toil 125(3) 72-78 (Mar 2010)

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Today, nanotechnology is recognized as enabling the manipulation of matter at the atomic and molecular level to create new materials with functional characteristics that are markedly different from conventional materials. Nanoemulsions, for example, can be used to control the rate at which assets are delivered to the skin. This control is achieved by incorporating materials within the nanoemulsion according to their compatibility with it, which obviously relies on their physical-chemical structure. Indeed, a great deal of attention has been dedicated recently to colloidal systems for the delivery of active ingredients because they significantly reduce the side effects of drugs and increase their bioavailability.

Besides delivery, nanoemulsions exhibit improved stability over conventional systems, such as liposomes or solid lipid nanoparticles, since their small particle sizes are less affected by gravity and less inclined to settle during storage, thus preventing flocculation and increasing shelf life. The particles also prevent coalescence due to their uniform shape. Furthermore, the significant thickness of the particle film, relative to the particle diameter, prevents its thinning or rupture; and wetting, spreading and penetration can be improved as a result of the low surface tension.

The size of nanoemulsion particles is a key factor in their efficient transdermal delivery; their large surface area and small size ensure uniform deposition on skin, thus increasing the rate of skin absorption and hydration potential. In order to reduce particle size, physical means are used. High pressure homogenization is the preferred technology since it can be used on a wide range of compositions. This pressure typically is applied in two stages—high pressure at first, followed by low pressure. High pressure homogenizers are manufactured by various companies and the end product will vary with the brand and model used.

Besides pressure, the number of homogenization cycles or passes used during the two stages can affect the particle size in the end product. The chemical composition and concentration of emulsifier used can also impact the nanoemulsion. Finally, the temperature at which the nanoemulsion is homogenized influences its production; Aubrun et al. and Liedtke et al. observed that higher homogenization temperatures resulted in smaller particles. Thus, the objective of the present work was to examine formulations prepared with similar oil fractions but different emulsifier systems and process parameters to determine why their behaviors differ. Understanding these dynamics would thus determine which conditions, among those studied, is optimal for formulating nanoemulsions.

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Table 1. Summary of conditions studied for each system emulsifier

Table 1. Summary of conditions studied for each system emulsifier

Samples were prepared by varying the type of emulsifier, the first stage homogenizing pressure (60 MPa and 120 MPa), and the number of cycles to investigate the effects of these variables on nanoemulsion characterization.

Table 2. Particle size (nm) and distribution of the ethoxylated emulsifier system

Table 2. Particle size (nm) and distribution of the ethoxylated emulsifier system

Particle size (nm) and distribution in terms of number (N) and volume (V) in nanoemulsions prepared using up to eight homogenization cycles (first-stage pressure = 120 MPa @ 20°C)

Table 3. Particle size (nm) distribution for nanoemulsions incorporating the exthoxylated system, inulin and potassium cetyl phosphate

Table 3. Particle size (nm) distribution for nanoemulsions incorporating the exthoxylated system

Particle size (nm) distribution in terms of number (N) and volume (V) over various cycles of homogenization (pressures = 60 MPa and 120MPa @ 20°C)

Figure 1. Comparison of particle size

Figure 1. Comparison of particle size

Comparison of particle size by volume through the cycles of homogenization pressure of 120 MPa for the emulsifiers used

Figure 2: Comparison of viscosity

Figure 2: Comparison of viscosity

Comparison of viscosity in cP (20 rpm/20°C) before and through the various cycles of homogenization pressure

Footnotes [Knapik 125(3)]

a The Labortechnik model RW 20 agitator used for this study is manufactured by IKA.
b The Ultra Turrax Labortechnik model T25 basic turbo-agitator used for this study is manufactured by IKA.
c The NIRO SOAVI SpA model NS 100 1L 2K high pressure homogenizer used for this study is manufactured by GEA Niro Soavi S.p.A.
d The Particle Size Analyzer, model LS 13 320, used for this study is manufactured by Beckman Coulter LS.
e Mili Q Water series Blen 35148-A/JBRQlVO 06 is a product of Millipore Gradient.
f The 3510MTH ultrasound treatment used for this study is manufactured by Branson.
g The Brookfield digital model RV DV II + viscosimeter used for this study is manufactured by Brookfield.

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