Proteins as supramolecular hosts for C₆₀: A true solution of C₆₀ in water

Hybrid systems have great potential for a wide range of applications in chemistry, physics and materials science. Conjugation of a biosystem to a molecular material can tune the properties of the components or give rise to new properties. As a workhorse, here we take a C₆₀@lysozyme hybrid. We show that lysozyme recognizes and disperses fullerene in water. AFM, cryo-TEM and high resolution X-ray powder diffraction show that the C₆₀ dispersion is monomolecular. The adduct is biocompatible, stable in physiological and technologically-relevant environments, and easy to store. Hybridization with lysozyme preserves the electrochemical properties of C₆₀. EPR spin-trapping experiments show that the C₆₀@lysozyme hybrid produces ROS following both type I and type II mechanisms. Due to the shielding effect of proteins, the adduct generates significant amounts of ¹O₂ also in aqueous solution. In the case of type I mechanism, the protein residues provide electrons and the hybrid does not require addition of external electron donors. The preparation process and the properties of C₆₀@lysozyme are general and can be expected to be similar to other C₆₀@protein systems. It is envisaged that the properties of the C₆₀@protein hybrids will pave the way for a host of applications in nanomedicine, nanotechnology, and photocatalysis.