Cyclodextrins are formed during the enzymatic degradation of starch. They are macrocyclic polysaccharides built from glucose units covalently linked at the C1 and C4 carbon atoms. Depending on the number of glucose units, one distinguishes between a- (six), b- (seven) and g-cyclodextrins (eight monomer units). These molecules are torus shaped (Figure 1).
The cyclodextrins are rather rigid molecules with a preformed cavity. In these cavities, hydrophobic substances or part of them can be included. For many years cyclodextrins were only available in small quantities at high prices. Thus only a few special applications seemed to be suitable for these molecules. Due to improvements in cyclodextrin production, their prices decreased during the last 20 years and an increasing number of applications have been reported in the literature. Up to now cyclodextrins have been used primarily in pharmaceutics,cosmetics and food.
Some years ago, the permanent fixation of cyclodextrins on textile surfaces was described in the literature. A cyclodextrin derivative suitable for the fixation on cotton fibers is already commercially available. This offers some new and until now unknown applications of textile materials in direct contact with the skin. The aspects for cosmetic formulations will be discussed in this article.
The results of different relevant experimental studies with cyclodextrins have been summarized. No disadvantages for the use of cyclodextrins and their derivatives in dermal applications could be concluded from the literature. As a result, cyclodextrins are already used in pharmaceutic and cosmetic products for the delivery of drugs. A relatively large number of cosmetic products with cyclodextrins is already available on the market.
For the use in textile finishing, β-cyclodextrin modified with a reactive group (monochlorotriazinyl group) is used. This anchor group reacts with the hydroxyl groups of cellulose or with the amino groups of wool and silk. Some toxicological data on this cyclodextrin derivative have been already reported (Table 1). According to guidelines from the Organisation for Economic Co-operation and Development concerning testing of chemicals, this cyclodextrin derivative has no irritating or sensitizing effects. Thus comparable results for textile materials finished with this derivative are expected. This expectation is supported by the first clinical trials using T-shirts with fixed cyclodextrins. No irritation of the human skin could be detected.