DO CARBON NANOTUBES INHIBIT OR PROMOTE AMYLOID FIBRILS FORMATION?

Abstract

Background: Carbon nanotubes, due to their unique physical properties, have been widely used in materials science and electronics; however, numerous attempts to create systems for delivering drugs or complexes of therapeutic drugs with nanotubes for improving their effectiveness and specificity have not succeeded. It is primarily due to the high cytotoxicity of nanotubes for living cells as well as the lack of mechanisms for their biodegradation. On the other hand, carbon nanotubes can form stable compounds with such biologically important molecules as DNA, phospholipids, proteins. In this paper, the possibility of the formation of amyloid fibril structures in lysozyme due to the interaction with carbon nanotubes is shown. The obtained results have both a fundamental and an applied value, since this may be a method for obtaining model amyloid fibrils for further study. Objectives: The purpose of the work was to study the effect of carbon nanotubes on the formation of fibril structures in lysozyme at room temperature under different pH values. Materials and methods: For the preparation of the samples, hen egg-white lysozyme protein (HEWL, Fluka), as well as single-walled (SWCNT, Sigma-Aldrich) and multi-walled (MWCNT, OOO TM “Spetsmash”, Kyiv, Ukraine) carbon nanotubes were used. Used techniques: IR-Fourier Absorption Spectroscopy; confocal microscopy. Results: In this paper, the study of molecular mechanisms of interaction of lysozyme with carbon nanotubes by vibrational spectroscopy was carried out and a conformational analysis of the formed complexes was performed. It is shown that carbon nanotubes can affect the structure of lysozyme even at room temperature and normal pH values, as evidenced by conformational changes in lysozyme due to interaction with carbon nanotubes. Complexes which are formed as a result of such interaction, have characteristic features of amyloid fibrillar structures. It reveals one of possible mechanisms of carbon nanotubes cytotoxicity. On the other hand, such a technique can be introduced to obtain model amyloid fibrils for further study. Conclusion: The method of vibtarional spectroscopy has shown that carbon nanotubes can influence the structure of lysozyme, as it is shown by the conformational analysis of the absorption band Amide I. After the interaction of lysozyme with CNT, an increase in the contribution of antiparallel β-conformation in the structure of lysozyme is observed, and the contribution of the α-helix conformation is reduced, which are characteristic features in the formation of fibrillar structures. The possibility of amyloid fibril formation without the use of high temperatures at different pH values with the interaction of lysozyme and carbon nanotubes, which can be applied as a method for obtaining the model amyloid fibrils, is shown.