Functionalization Of Multiwalled Carbon Nanotubes For Highly Selective Isolation Of Albumin

As a kind of biological macromolecules with bioactivity, proteins generally have poor stabilities. They tend to undergo significant conformational change in the process of purification, and adsorption-induced changes in the structure and dynamics have been observed which might reduce the biological activity of the proteins. In practice, the acquisition of high purity proteins from complex sample matrixes is a key issue for the development of proteomics. In this respect, a significant challenge is to develop new advanced materials for selective isolation of proteins from real world biological samples.A cationic hyperbranched polymer polyethyleneimine (BPEI) was immobilized on the surface of multiwalled carbon nanotubes (MWNTs) via electrostatic interaction between the positively charged protonated amines within the polymer and the carboxyl groups on the chemically oxidized MWNTs surface. The functionalized material of BPEI-MWNTs was characterized by FT-IR, TGA, TEM and surface charge analysis (Zeta potential), and it was used as a bio-sorbent for the adsorption of proteins, which exhibits high selectivity for bovine serum albumin (BSA) in the presence of other acidic and basic proteins with different isoelectric points. In practice, a micro-column packed with BPEI-MWNTs was incorporated into a sequential injection system for performing on-line separation and preconcentration of BSA in phosphate buffer, and the retained BSA was effectively recovered with citrate buffer as stripping reagent. The circular dichroism (CD) spectra showed no conformational change of BSA during the adsorption/desorption process. A dynamic adsorption capacity of167mg g-1for BSA was achieved, offering a6-fold improvement over that achieved by using linear polyelectrolyte poly(diallyldimethylammonium chloride) wrapped MWNTs. With a sample volume of2.0mL, an enrichment factor of10was obtained along with an adsorption efficiency of100%, a recovery of100%, a sampling frequency of10h-1and a RSD of2.6%at25μg mL-1BSA. The method was demonstrated by processing human whole blood for the selective isolation of human serum albumin, achieving satisfactory results as demonstrated by assay with SDS-PAGE.