Enzyme and Microbial Technology 40 (2007) 1646–1650 Rapid communication Cotton fabric: A natural matrix suitable for controlled release systems Snezhana Bogomilova Todorova a , Carla J.S.M. Silva b , Nikolay Petkov Simeonov a , Artur Cavaco-Paulo b,∗ a Department of Textile Engineering, University of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria b Department of Textile Engineering, University of Minho, 4800-058 Guimar˜ aes, Portugal Received 26 February 2007; accepted 26 February 2007 Abstract The possibility to use cotton as a matrix for controlled release systems was studied by covalently attaching a model compound, specifically the reactive dye Remazol Brilliant Blue R to its surface. Afterwards the fabric was coated with a commercial cellulase. The release of the dye, obtained by the hydrolysis of cotton fibres in sweat buffer, was monitored. The reducing sugars concentration increased for both fabrics (with and without the dye covalently fixed) while the increase in the absorbance was only attained for the dyed cotton, as expected. These results confirm the viability of using cotton as a natural matrix for controlled released systems while presenting a promising approach to immobilize covalently other substances in cotton garments, like fragrances, which could be released by the action of human sweat. © 2007 Elsevier Inc. All rights reserved. Keywords: Cellulases; Controlled release systems; Cotton fabric; Glutaraldehyde 1. Introduction Cellulases are a group of hydrolytic enzymes able to hydrol- yse cellulose that play an important role in maintaining the carbon balance in nature. There are three types of enzymes which have been traditionally assigned to the cellulase system: endoglucanases (EG) which cleave randomly cellulose chains (EC 3.2.1.4), cellobiohydrolases (CBH) which cleave cellobiose from the chain ends (EC 3.2.1.91), and -glucosidases which hydrolyses cellobiose into glucose (EC 3.2.1.21). Of the three classes of enzymes, EG are the less specific ones, since they can also hydrolyse cellulose derivatives like carboxymethyl cel- lulose and reactive dyed cotton. This fact is mainly due to the geometry of the active site of those enzymes which is of a tunnel shape for CBHs and of a cleft shape for EGs [1]. Considering those fundamental facts, our research group con- jectured the hypothesis that cellulases could be used as an agent to release drugs linked to cotton fabrics, where the addition of the enzyme could be the agent to “switch on” the release of the drug in an aqueous medium. The release of the enzyme is not however desirable in the environment where the drug should be released to. Therefore, another possibility to allow for the drug delivery ∗ Corresponding author. Fax: +351 253 510293. E-mail address: artur@det.uminho.pt (A. Cavaco-Paulo). is to coat the fibres with the enzyme, where the drug had been previously covalently bound. The coating process could be per- formed using glutaraldehyde at low temperatures, inhibiting in this way the catalytic action of the enzyme. It has been reported that cellulases are stable when immobilized closely by their sub- strates, especially in dry conditions [2–4]. Consequently, if the enzyme is crosslinked around the fibre containing the drug, the water environment could be the “switch on” factor for the release of that specific drug. In this study a reactive dye was used as a drug model and cotton fabric was used as the support for a potential application into a drug release system, as shown in Fig. 1. To provide evidence of the concept, the dye was covalently attached to the fibre and subsequently a cellulase was cross linked to the fibre surface using glutaraldehyde. The water envi- ronment was used as the “switch on” agent to release the dye. The mechanism for the release of the drug proceeds via the hydrol- ysis of the substrate (cellulose) with the concomitant release of the covalently attached dye and of soluble reducing sugars. 2. Material and methods 2.1. Enzyme, chemicals and fabric The enzyme Cellusoft L, a total cellulase from Trichoderma origin, was a gift from Aquitex (Porto, Portugal). All other chemicals used were of 0141-0229/$ – see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.enzmictec.2007.02.017