Potential of human cD-crystallin for hair damage repair: insights into the mechanical properties and biocompatibility A. Ribeiro* † , T. Matam a* † , C. F. Cruz* † , A. C. Gomes † and A. M. Cavaco-Paulo* *IBB-Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057, Braga, and † Department of Biology, Centre of Molecular and Environmental Biology (CBMA), Universidade do Minho, Campus de Gualtar, 4710-057, Braga, Portugal Received 25 January 2013, Accepted 02 May 2013 Keywords: Greek key motif, hair treatment, human crystallin, mechanical properties improvement, over bleached hair Synopsis OBJECTIVES: The objective of this work was to develop a new strategy to physically ‘repair’ chemically damaged hair. Hence the human eye cD-crystallin, a protein from the superfamily character- ized structurally by the Greek key motif, was studied. The human cD-crystallin was chosen based on the ability of proteins belonging to this superfamily to be involved in the coating of specific struc- tures. Two crystallins were used on the study, the wild type (Pro- tein Data Bank ID: 1HK0) and the mutant protein. The mutant form was intended to induce a strong and quick protein polymeri- zation as well to have new possible points of anchorage to hair. METHODS: The ability of both crystallins to bind to damaged hair and even penetrate into its cortex was checked by fluorescence microscopy, confocal microscopy and scanning electron micros- copy. Furthermore the reinforcement of hair mechanical resistance, the potential cytotoxic/inflammatory effect of crystallins were stud- ied in order to have a fully comprehension about the protein based formulation. RESULTS: Although the chemical over-bleaching treatment induced a decrease of 20% on the resistance of the hair, the crys- tallins which bind and penetrate the hair fibre were able to recover and even to improve its mechanical properties when compared to the virgin hair. Moreover none of the crystallins displayed a toxic effect in fibroblasts for all the range of tested concentrations upon 72 h of exposure. The active aggregation process of mutant crystal- lin induced an inflammatory response in fibroblasts in the first 24 h of contact, measured by the amount of released pro-inflam- matory cytokine IL-6 to the medium. In contrast contact with wild type crystallin did not lead to significant inflammation. CONCLUSION: Outcome from protein formulation characterization supports the hypothesis that the cD-crystallin it is able to recover and improve the mechanical properties of chemical damaged hair. Therefore it can be considered as a very promising strengthening agent for the development of new restorative hair care products. R esum e OBJECTIFS: L’objectif de ce travail  etait de d evelopper une nou- velle strat egie pour physiquement “r eparer” les cheveux chimique- ment endommag es. La prot eine humaine cD-cristalline, une prot eine de la superfamille caract eris ee structurellement par le motif cl e grecque, a  et e  etudi ee. Le cD-cristallin humain a  et e choisi en fonction de la capacit e des prot eines appartenant  a cette super- famille d’^ etre impliqu ees dans le rev^ etement des structures sp ecifi- ques. Deux cristallins ont  et e utilis es dans l’ etude, le type sauvage (Protein Data Bank ID: 1HK0) et la prot eine mutante. La forme mutante  etait destin ee  a induire une polym erisation de la prot eine, forte et rapide ainsi d’avoir de nouveaux points d’ancrage possibles aux cheveux. M  ETHODES: La capacit e des deux cristallins de se lier aux chev- eux ab ^ ım es et m^ eme de p en etrer dans le cortex a  et ev erifi ee par microscopie  a fluorescence, microscopie confocale et la microscopie  electronique  a balayage. En outre, le renforcement de la tenue m ecanique des cheveux, l’effet cytotoxique/inflammatoire potentiel de cristallins ont  et e  etudi es en vue d’avoir une compr ehension compl  ete de la formulation  a base de ces prot eines. R  ESULTATS: Bien que le traitement chimique de sur-blanchiment induise une diminution de 20% de la r esistance des cheveux, les cristallins qui se lient et p en etrent la fibre capillaire ont pu r ecup erer et m^ eme d’am eliorer ses propri et es m ecaniques par rap- port aux cheveux non-trait es. Par ailleurs aucun des cristallins n’affiche d’effet toxique dans les fibroblastes pour toute la gamme des concentrations test ees sur les 72 heures suivant l’exposition. Le processus d’agr egation active du cristallin mutant induit une r eponse inflammatoire dans les fibroblastes dans les premi eres 24 he- ures de contact, mesur ee par la quantit e de s ecr etion de cytokine pro- inflammatoire IL-6 dans le milieu. Par contre, le contact avec le type sauvage de cristallin n’a pas conduit  a une inflammation notable. CONCLUSION: Le r esultat des  etudes de la caract erisation et de la formulation de prot eines soutient l’hypoth ese que le cD-cristallin est capable de r ecup erer et d’am eliorer les propri et es m ecaniques des cheveux ab ^ ım es chimiquement. Par cons equent, il peut ^ etre consid er e comme un agent de renforcement tr es prometteur pour le d eveloppe- ment de nouveaux produits de soins capillaires r eparateurs. Introduction Hair plays a key role in our appearance and reflects our physical state. Therefore, there is great interest in the development of new hair care products that facilitate repair and prevent adverse effects on the capillary structure. Cosmetics to adorn or to change the appearance of scalp hair are widely used in any society. Correspondence: Artur Cavaco-Paulo, Department of Biological Engi- neering, Campus de Gualtar, University of Minho 4710-057 Braga, Portugal. Tel.: (+351) 253604310; fax. (+351) 253678980; e-mail: artur@deb.uminho.pt © 2013 John Wiley & Sons Ltd 1 International Journal of Cosmetic Science, 2013, 1–9 doi: 10.1111/ics.12065