Multi-walled carbon nanotubes as a platform for Immunoglobulin G attachment

Abstract

Nanomaterials have been extensively used in different applications due to their peculiar characteristics and nanoscale dimensions. Among nanoparticles, carbon-based nanomaterials are becoming highly attractive for biomedical applications such as diagnosis, tissue engineering, drug delivery, and biosensing. The conjugation of carbon-based nanomaterials with antibodies combines the properties of these materials with the specific and selective recognition ability of the antibodies to antigens. The present work proposes a process intensification approach for immunoglobulin G (IgG present in rabbit serum) attachment on multi-walled carbon nanotubes (MWCNTs) in a single step. The effect of several parameters, namely MWCNTs external diameter, rabbit serum concentration, MWCNTs functionalization and pH value, on the IgG attachment yield was evaluated. The dilution of rabbit serum decreased other protein attachment, namely rabbit serum albumin (RSA), while increasing the IgG yield to 100%. The interaction mechanisms between IgG and MWCNTs were evaluated at pH 5.0 to 8.0. The protonation of IgG amino acids indicates that N-term are the most reactive amino acids in the antibody structure. The identification of the N-term reactivity at pH 8.0 allows to indicate a possible orientation of the antibody over the MWCNTs surface, described as “end-on”. Since the amount of RSA attached to MWNT decreased with the increase in serum dilution, the IgG orientation and amine activity was not affected. This orientation demonstrates that the IgG attachment over the surface of the MWCNTs could be an effective strategy to maintain the antigen recognition by the antibody, and to be used for biomedical applications.