Catalytic and Electron Conducting Carbon Nanotube Reinforced Lysozyme Crystals

Abstract

Novel reinforced cross-linked lysozyme crystals containing homogeneous dispersions of single-walled carbon nanotubes (SWCNTs) have been produced and characterized. The incorporation of SWCNTs inside lysozyme crystals gives rise to reinforced hybrid materials with tunable mechanical strength and electronic conductivity, while preserving the crystal-quality and morphology. These reinforced crystals show increase catalytic activity at higher temperature, being active even above the denaturation temperature. The electron transport through the crystals have been linked to the content and distribution of SWCNTs inside the crystals. The electron conduction through the crystals is isotropic and very efficient, presenting high conductivity values up to 600 nS at very low (0.05 wt%) SWCNTs concentration. To obtain these crystals a new protocol based on the in situ crystallization of lysozyme in hybrid SWCNTs-peptide hydrogels has been developed. These peptide hydrogels have been able to homogeneously dispersed hydrophobic SWCNTs allowing first, the crystallization of the enzyme lysozyme and secondly, transferring the new properties of the inorganic component to the crystals. Taken together, these hybrid crystals represent a notorious example of the versatility of proteins as biological substrates in the generation of novel functional materials, opening the door to use them in catalysis and bioelectronics at macroscale.