Modified Denatured Lysozyme Effectively Solubilises Fullerene C60 Nanoparticles in Water

Carbon based nanomaterials, like fullerenes, nanotubes and graphene, have several applications in the medical field and engineering field, however the very low solubility of these materials both in organic solvents and in... [ view full abstract ]

Carbon based nanomaterials, like fullerenes, nanotubes and graphene, have several applications in the medical field and engineering field, however the very low solubility of these materials both in organic solvents and in water poses serious limitations to their use. For example, fullerene C60, the most studied among fullerenes, can be dissolved in water in the form of nanoparticles of variable dimensions only through several weeks of sonication or using complex procedures involving organic solvents. For this reason the development of “solubilizing agents” for carbon materials is a very active research area. We have compared the efficacy as solubilizing agent of native and denatured hen egg white lysozyme, a highly basic protein. In order to obtain a denatured, yet soluble, lysozyme derivative, the four disulfides of the native protein were reduced and exposed cysteines were alkylated by 3-bromopropylamine, thus further increasing the already high positive charge of the native protein. Circular dichroism studies demonstrated that modified denatured lysozyme (amino-propyl-lysozyme, AP-LYS) is a random coil in water but can adopt a helical structure in organic solvents. Both native lysozyme and AP-LYS proved to be very effective solubilizing agents for C60 however dynamic light scattering, transmission electron microscopy and atomic force microscopy studies showed that AP-LYS allows to prepare more homogeneous and more stable C60 nanoparticles using lower amounts of protein.
Preliminary studies shows that AP-LYS can be also used to solubilize in water other carbon allotropes.