Nanomaterial–protein interactions: the case of pristine and functionalized carbon nanotubes and porcine gastric mucin

Mucus represents a serious obstacle that prevents the penetration of drug carrier's transport across the mucus barrier. This study highlights the interaction between mucin glycoprotein, mucin from porcine stomach Type III (PGM) and different pristine and functionalized single-wall and multi-wall carbon nanotubes (CNTs), under physiological conditions, in order to investigate the affinity of different CNTs to mucin. This aspect could be of the utmost importance for the use of CNTs for biomedical purposes. The interaction between CNTs and PGM was investigated by using different techniques like fluorescence steady-state spectroscopy, thermogravimetric analysis (TGA), dynamic light scattering (DLS), circular dichroism (CD), electrophoresis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We demonstrated that mucin has impressive capabilities for binding CNTs in physiological solutions. Moreover, we proved that the nanomaterial–protein interaction is influenced by the different natures of the tubes (SW and MW) and by their different functionalizations (pristine and oxidized CNTs).