An Alkylpolyglucoside Surfactant as a Prospective Pharmaceutical Excipient for Topical Formulations: The Influence of Oil Polarity on the Colloidal Structure and Hydrocortisone Permeation

There is a growing need for research into new skin- and environment-friendly surfactants. This paper focuses on a natural surfactant of an alkylpolyglucoside type, which can form both thermotropic and lyotropic liquid-crystalline phases. The aim of this study was to relate some physicochemical properties (characterised by polarisation and transmission electron microscopy, thermal analysis and rheology) of the three formulations based on cetearyl glucoside and cetearyl alcohol, to the results of in vitro and in vivo bioavailability of hydrocortisone (HC). The three formulations contained oils of different polarity (medium chain triglycerides: MG, isopropyl myristate: IPM and light liquid paraffin: LP), respectively. In vitro permeation was followed through the artificial skin constructs (ASC), while the parameters measured in vivo were erythema index: EI (using instrumental human skin blanching assay), transepidermal water loss (TEWL) and stratum corneum hydration (SCH). The vehicles based on cetearyl glucoside and cetearyl alcohol showed a complex colloidal structure of lamellar liquid-crystalline and lamellar gel-crystalline type, depending on oil polarity. Rheological profile of the vehicle was directly related to the in vitro profile of the HC permeation. In vivo results suggested that the vehicle with MG retarded the HC permeation, whereas less polar IPM and non-polar LP enhanced it. It is suggested that the enhancement is achieved either by a direct interaction with lipid lamellae of the SC or indirectly by improving skin hydration.

There were no adverse effects during in vivo study, which indicates a good safety profile of this alkylpolyglucoside surfactant.

Cosmetic science is a science-based, but fashion-led discipline. It covers a wide range of intersecting subjects, including biological sciences, dermatology, applied chemistry and physics.

Given widespread ecological concerns, there is a growing need for research into new environmentally friendly surface-active materials, including emulsifiers used in skin products. This paper focuses on the properties of a new natural sucrose-derived emulsifier named cetearyl glucoside & cetearyl alcohol.

The aim of this pre-formulation study was to establish, for the first time, the relationship between physicochemical properties of the topical emulsions based on cetearyl glucoside & cetearyl alcohol, and the results of in vitro and in vivo bioavailability of a topical active – hydrocortisone. Results obtained revealed details of a complex colloidal structure of the test emulsions, its dependence on the oil polarity, and its relationship with the drug release profile.

The range of instrumental methods required for the planned comprehensive evaluation necessitated a multi-centre study. Polarisation and transmission electron microscopy were performed at Technical University, Braunschweig, thermal analysis and rheology at London College of Fashion, while in vitro HC permeation and in vivo randomised testing were carried out at the Faculty of Pharmacy, Belgrade.

Dr Slobodanka (Danka) Tamburic is a Reader in Cosmetic Science and a Programme Director for Cosmetic Science courses at London College of Fashion.

She has a background in Pharmacy, with an MSc in Pharmaceutical Technology and a PhD in Pharmaceutical Sciences. This was followed by three years of post-doctoral experience at the Centre for Materials Science, School of Pharmacy London. In the year 2000, she started the first graduate course in the UK solely devoted to the cosmetic industry - the BSc (Hons) in Cosmetic Science at London College of Fashion. Her current research encompasses the following strands:

* Exploring the efficacy of cosmetic products using skin bio-engineering methods (non-invasive in vivo testing)
* Evaluating internal structure of semisolid systems for cosmetic and pharmaceutical application and its effect on product efficacy
* Exploring the use of novel technology (especially nanotechnology) in cosmetics
* Biotechnological approach as a method for obtaining novel multifunctional cosmetic ingredients

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