Functionalization of Wool with L-Cysteine: Process Characterization and Assessment of Antimicrobial Activity and Cytotoxicity Isabel C. Gouveia, 1,2 Daniela Sa ´, 3 Mariana Henriques 4 1 Textile Department, University of Beira Interior, 6201-001Covilha ˜-Portugal 2 R&D Unit of Textile and Paper Materials, University of Beira Interior, 6201-001Covilha ˜-Portugal 3 Chemistry Department, University of Beira Interior, 6201-001Covilha ˜-Portugal 4 Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal Received 19 April 2010; accepted 1 February 2011 DOI 10.1002/app.34587 Published online 18 October 2011 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: This investigation reports a new biotechno- logical process that uses L-cysteine (L-Cys) which provides a permanent, nontoxic and effective antimicrobial effect over wool-based materials. This process is simple and carried out via widespread exhausting methods. Typically, wool fabrics are incubated with L-Cys for 50 min at 60  C in a pH 4.8 ace- tate buffer solution 25 mM, under mild agitation to give a good absorption rate. The minimal inhibitory concentration (MIC) of L-Cys was evaluated by the NCCLS M07-A6 stand- ard method, and the results showed a good antibacterial ac- tivity against S. aureus and K. pneumoniae within the range of 6.0  10 3  4.8  10 2 g/mL [MIC 0.6% (w/v)] and 6.0  10 3  4.8  10 2 g/mL [MIC 0.6% (w/v)], respectively. In addition, the antimicrobial activity of the functionalized wool was assessed by the international standard JIS 1902- 2002 showing a good inhibition of bacterial growth for an L-Cys concentration of 1% over the weight of fabric, both against Staphylococcus aureus and Klebsiella pneumoniae. More- over, the biocidal mechanism was found to be related with the increase of sulfhydryl’s groups onto wool fibers, which were quantified by the Ellman’s reagent (5,5 0 -Dithio-bis(2- nitrobenzoic acid) method. The new process is easy to per- form, non toxic, preserve wool quality and is a novel biomi- metic approach that uses antimicrobial amino acids and may open new avenues for the design of biomedical textiles with a broad range of applications in healthcare. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 1352–1358, 2012 Key words: antimicrobial textiles; biopolymers; S. aureus; K. pneumoniae; sulfhydryl groups; Ellman’s reagent INTRODUCTION Antimicrobial textiles are frequently used in medi- cal/hospital, pediatric, and geriatric fields. In the past, these products were processed and treated using chemicals that would often yield highly toxic or if not undesirable by-products. Moreover, some of these processes and products may alter or even damage the fundamental properties of the compo- nent fibers which may cause a product to be less effective in its intended use. Consequently, there have been constant efforts to develop more ecologi- cal, effective, and property-preserving processes. 1–5 Several methods have been developed to give antimicrobial properties to textile materials. 1–7 In addition, various antimicrobial agents have been tested in textiles. Quaternary ammonium com- pounds, silver, polyhexamethylene biguanides, and triclosan have been used with success. They have powerful bactericidal activity as indicated by the MIC values (minimal inhibitory concentration). However, the majority have a reduced spectrum of microbial inhibition and may cause skin irritation, ecotoxicity, and bacterial resistance, and very few processes have been developed toward wool-based materials. 1–7 Moreover, their incorporation in the textiles reduces the bioactivity substantially and lim- its availability, compelling the raised concentrations to be used in the functionalization process. Likewise, the biocide can gradually lose activity during the use and launderings of the textile. Thus, great amounts of these biocides are applied to the textiles to control the bacterial growth efficiently and to keep its durability. 2,3 To overcome these disadvantages, natural com- pounds mostly chitosan and plant extracts are being tested as antimicrobial agents for textiles. 2,4,5 Also, the requirement of the consumers for hygienic clothes and the growing market of medical and Correspondence to: I. C. Gouveia (igouveia@ubi.pt). Contract grant sponsor: FCT; contract grant number: PTDC/EBB-BIO/113671/2009. Contract grant sponsor: R and D Unit of Textile and Paper Materials, Faculty of Engineering, University of Beira Interior. Journal of Applied Polymer Science, Vol. 124, 1352–1358 (2012) V C 2011 Wiley Periodicals, Inc.