Effects of single-walled carbon nanotubes on lysozyme gelation

• Single-walled carbon nanotubes were dispersed in lysozyme solutions, at pH 2.0.
• Thermal gelation of the dispersions was induced.
• Characterization by DLS, rheology and other physico-chemical methods followed.
• The sol–gel transition temperature was determined by both DLS and rheology.
• Depending on nanotube/lysozyme mole ratios, gels are diluted or bicontinuous.

The possibility to disperse carbon nanotubes in biocompatible matrices has got substantial interest from the scientific community. Along this research line, the inclusion of single walled carbon nanotubes in lysozyme-based hydrogels was investigated. Experiments were performed at different nanotube/lysozyme weight ratios. Carbon nanotubes were dispersed in protein solutions, in conditions suitable for thermal gelation. The state of the dispersions was determined before and after thermal treatment. Rheology, dynamic light scattering and different microscopies investigated the effect that carbon nanotubes exert on gelation. The gelation kinetics and changes in gelation temperature were determined. The effect of carbon and lysozyme content on the gel properties was, therefore, determined. At fixed lysozyme content, moderate amounts of carbon nanotubes do not disturb the properties of hydrogel composites. At moderately high volume fractions in carbon nanotubes, the gels become continuous in both lysozyme and nanotubes. This is because percolating networks are presumably formed. Support to the above statements comes by rheology.

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