© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 4261 www.advmat.de www.MaterialsViews.com COMMUNICATION wileyonlinelibrary.com Adv. Mater. 2011, 23, 4261–4264 Netta Hendler, Bogdan Belgorodsky, Elad D. Mentovich, Michael Gozin,* and Shachar Richter* Efficient Separation of Dyes by Mucin: Toward Bioinspired White-Luminescent Devices N. Hendler, B. Belgorodsky, E. D. Mentovich, Dr. M. Gozin, Dr. S. Richter School of Chemistry Faculty of Exact Sciences Tel Aviv University Ramat Aviv, Tel Aviv 69998, Israel E-mail: cogozin@mgchem.tau.ac.il; srichter@post.tau.ac.il N. Hendler, E. D. Mentovich, S. Richter University Center for Nanoscience and Nanotechnology Tel Aviv University Ramat Aviv, Tel Aviv 69998, Israel DOI: 10.1002/adma.201100529 The production of organic white-light-emitting devices is one of the main technological and scientific challenges in the field of optoelectronics [1–4] because the formation of such a broad emis- sion spectrum with the use of a single dye is difficult to accom- plish. [5,6] In practice, the emission of white light is achieved by the use of a mixture of the three primary dyes, which emit red (R), green (G), and blue (B) light. [7] However, as a result of non- radiative interactions between very close color elements, such as Förster resonance energy transfer (FRET), an undesirable shift in the emission spectrum is often observed, which prevents the achievement of white-light emission. [8] The two main approaches to resolving this problem are the construction of multilayers of dyes in which each separate layer consists of a single type of dye and the synthesis of a separating material in which the different emitting compounds can be mixed while separated by some minimal distance at which the dye interactions are negligible (matrix–filler materials). [9] Most of the common matrix materials consist of inorganic compounds that can be polymerized into thin films in which the different dyes, usually molecular dyes or polymeric species, can be incorporated. [10] While these systems are the leading candidates for the preparation of flexible, processable, and inex- pensive devices, [3,11] the fabrication process of such systems is greatly affected by environmental parameters such as humidity, temperature, and concentration. [11] Thus, control of the com- plex with its multi-ingredient phase diagram remains very chal- lenging and the search continues for simpler alternative matrix materials. [12,13] Here we suggest exploiting nature’s ability to form many types of stable and controllable host–guest systems [14–16] for the construction of a new type of robust matrix material and use the material for the construction of protein luminescent films (PLUF) and devices. This simple methodology involves the extraordinary capabilities of certain types of hydrophilic proteins to host hydro- phobic compounds without affecting their properties. [17,18] We show that simple blending of the guest dyes in a protein bioma- trix enables the formation of a variety of PLUFs, all excited by a common single wavelength, emitting at wavelengths ranging from pure R, G, and B to white. Furthermore, although most of the common dyes used for emitting devices are not water-soluble, the design of our new complexes enables the production of water- soluble materials under ambient and “green” conditions. In general, host–guest interactions play a crucial role in many vital biochemical processes, [17] including transport, solubility, catalysis, sensing, self-assembly, distribution ratios in immis- cible solvents, and drug–receptor interactions. It is no coinci- dence that these interactions are the basis of many biological systems, whose efficiencies will long continue to surpass that of synthetic systems by orders of magnitude. In practice, proteins are the most suitable candidates for our goals because of their large host–guest capacities and the types of interaction and the range of guest compounds that can be incorporated in the matrix. The latter are the most common biomolecules that play important roles in the interactions, storage, and transport of various exogenic materials. Among the important groups of proteins that are well known for their properties of binding and solubilization of hydrophobic lig- ands is the family of mucins. [19] These glycoproteins are major components in the mucus that coats the surfaces of cells that line the respiratory, digestive, and urogenital tracts. [20] Mucin proteins constitute more than 80% of the organic compo- nents of mucus and serve as a first line of defense and delivery mediator common to both the gastrointestinal and respiratory systems. [21] We have previously shown that bovine submaxillary mucin (BSM) protein is capable of binding and solubilizing water- insoluble nanomaterials in physiological solution. [19] Here we utilize the extraordinary uptake properties of BSM to engineer light-emitting solutions and PLUFs. The structure of BSM is shown in Figure 1. This biodendrimer compound is highly glycosylated, composed of 80% carbohydrates. Its oligosac- charide chains consist of 5–15 monomers, show moderate branching, and are attached to the protein core by O-glycosidic bonds to the hydroxyl side chains of serine and threonine and arranged in a “bottle-brush” configuration around the pro- tein core. The monomeric BSM units (MW ≈ 170 kDa) are connected via disulfide-rich domains and form a dendritic structure. The fluorescent BSM solutions and PLUFs were prepared using several types of commercially available hydrophobic light- emitting dye molecules as fillers (Figure 1). Physical separa- tion between the dyes was achieved by separate incorporation of each type of dye in the BSM host followed by mixing an