Preparation and Properties of Small Nanoparticles for Skin and Hair Care

F. Zülli, F. Suter

SÖFW-Journal 123 (13): 880 - 885 (1997)

This article describes a method to prepare very small nanoparticles encapsulating different agents of cosmetic and pharmaceutical interest (Tretinoin, Retinol, Vitamin E Acetate, UV-filters, Fragrance).

Nanoparticles are small lipid vesicles formed by a monolayer of phospholipids. Whereas liposomes are typical carriers for hydrophilic substances, nanoparticles are the ideal delivery system to transport and protect lipophilic agents. The technique of high pressure homogenization at 1200 bar using a microfluidizer yields a 100% encapsulating of the oil in defined vesicles. The vesicle size has a great influence on the optical appearance of the nanoparticle dispersion. Preparations of particles with diameters of less than 60 nm are transparent dispersions of oil in water. These small nanoparticles show unique additional physical properties and offer new application possibilities.

The data show that nanoparticles are very stable and have a high affinity to the stratum corneum. Therefore, an enhanced bioavailability of the encapsulated material to the skin is achieved. We have also developed a nanoparticle delivery system to target the vesicles to hair. For that purpose, we have dotted the nanoparticle shell with cationic molecules thus producing a positively charged surface. Our experiments show that positively charged nanoparticles loaded with UV-filters have an almost one hundred fold higher affinity to hair than negatively charged particles.

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Small Lipid Nanoparticles: a New Delivery System of Lipophilic Agents to Hair and Scalp

F. Zülli and F. Suter

Elsevier / Hair research for the next millennium: 123-126 (1996)

The formulation of lipophilic agents in hair care products is unsatisfactory. Conventional oil-in-water emulsions of alcoholic hair tonics which are usually used to deliver lipophilic agents to hair and scalp perform poorly. They leave hair feeling sticky and greasy. In addition, only a low affinity of the substances to hair is observed.

In our laboratory, we have employed a new system to deliver hydrophobic agents to hair and scalp. The system consists of small water dispersible lipid nanoparticles. The vesicles are formed by a monolayer of phospholipids encapsulating a tiny oil core carrying lipophilic agents.

Compared to liposomes (optimal carrier for water-soluble drugs), the pay-load of lipophilic substances by nanoparticles is much higher. Nanoparticle preparations are quickly gaining wide recognition in the cosmetic field. They are also used as parenteral emulsions and in a few other pharmaceutical products.

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Application of Small Lipid Nanoparticles in In Vitro Mutation Assays

P. Leong-Morgenthaler, Centre de recherche Nestlé, Lausanne, Switzerland / Institute of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
J. Horlbeck, Centre de recherche Nestlé, Lausanne, SwitzerlandF. Suter, F. Zülli, Mibelle AG Biochemistry, Buchs, Switzerland

In Vitro Toxicology 10: 129-132 (1997)

We illustrate here the application of small lipid nanoparticles in genotoxicity testing using the human lymphoblastoid TK6 assay. The lipid nanoparticles were vesicles formed by lecithin encapsulating an oil core whose genotoxicity was to be evaluated. We show that the toxicities of nanoparticles were reflective of their lipid composition. Nanoparticles containing an isopropylmyristate oil core were found to be cytotoxic when present at 2.5% vol/vol in the medium. Those based on sunflower oil and triglycerides were not cytotoxic to TK6 cells when present at up to 5% vol/vol in the medium. These particles can also serve as convenient vehicles for oils and lipid soluble compounds. To check the efficiency of this delivery route, we compared the responses of TK6 cells treated with benzo(a)pyrene dissolved in DMSO or encapsulated in nanoparticles. The mutagenic responses observed in cells treated with benzo(a)pyrene solubilized in sunflower oil and delivered to the cells as nanoparticles were similar to those in cells treated with benzo(a)pyrene in DMSO. Nanoparticles were thus found to be efficient in delivering mutagens to cells in an in vitro mutation assay.

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Cell Toxicity of UV-A Irradiated Squalene

F. Zülli, E. Belser, S. Reutlinger, F. Suter

SÖFW-Journal 125 (12): 4 - 8 (1999)

UV-A irradiation is known to induce oxidative stress to the skin. The formation of free radicals causes skin lipid peroxidation and other harmful effects. Squalene is one of the main lipid components of the sebum and is particularly susceptible to photo-oxidation. To study the biological properties of UV-irradiated lipids, we have developed a novel method to deliver lipophilic compounds to cell cultures. The delivery system is based on a lipid nanoemulsion which is stabilized by phospholipids. In our experiments, we have studied the toxicity of a squalene nanoemulsion before and after UV-A irradiation on TK6 lymphoblastoid cells. We observed that UV-A exposure of squalene led to the formation of lipid peroxides and significantly increased the toxicity of the nanoemulsion to the cells. The addition of antioxidants, such as tocopherol and grape seed extract can reduce the formation of peroxides. It also had a positive effect on the toxicity of the UV-A irradiated nanoemulsion. Our results show that the developed test system based on lipid nanoemulsions and cell cultures is a new biological tool to study UV-A induced modifications in lipids.

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Cell Toxicity of UV-A Irradiated Lipids

F. Zülli, E. Belser, S. Reutlinger, F. Suter

Cosmetic Science Business: 118 - 120 (2000)

UV-A irradiation is known to cause an oxidative stress to the skin. The formation of free radicals results in skin lipid peroxidation and other harmful effects. Squalene, one or the main lipid components of the sebum is particularly susceptible to photo-oxidation. We have investigated the in-vitro formation of lipid peroxides upon UV-A irradiation of squalene and other lipids. To study the biological properties of UV-irradiated lipids, we have developed a novel method to deliver lipophilic compounds to cell cultures. The delivery system is based on a lipid nanoemulsion which is stabilised by phospholipids. In our experiments, we have studied the toxicity of encapsulated squalene and other lipids on TK6 lymphoblastoid cells before and after UV-A irradiation. UV-A irradiation of the nanoemulsions lead to the formation of lipid peroxides. However, the obtained values depend strongly on the encapsulated oil and the method applied to determine the peroxides. We found that the lipids in the form of nanoemulsions are reasonably well tolerated by the cells. But UV-A exposure of the nanoemulsions significantly increased their toxicity. Our results show that the developed test system based on lipid nanoemulsions and cell cultures is a new biological tool to study UV-A induced modifications in lipids. The data proof that low dose UV-A irradiation can already form very toxic compounds in skin lipids such as squalene.

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