Magnetized carbon nanotubes for visual detection of proteins directly in whole blood

The authors describe a magnetized carbon nanotube (MCNT)-based lateral flow strip biosensor for visual detection of proteins directly in whole blood avoiding complex purification and sample pre-treatments. MCNT were synthesized by coating Fe3O4 nanoparticles on the shortened multiwalled carbon nanotube (CNT) surface via co-precipitation of ferric and ferrous ions within a dispersion of shorten multiwalled CNTs. The antibody-modified MCNTs were used to capture target protein in whole blood; the formed MCNT-antibody-target protein complexes were applied to the lateral flow strip biosensor, in which a capture antibody was immobilized on the test zone of the biosensor. The captured MCNTs on the test zone and control zone were producing characteristic brown/black bands, and this enabled target protein to be visually detected. Quantification was accomplished by reading the intensities of the bands with a portable strip reader. Rabbit IgG was used as a model target to demonstrate the proof-of-concept. After systematic optimizations of assay parameters, the detection limit of the assay in whole blood was determined to be 10 ng mL−1 (S/N = 3) with a linear dynamic range of 10–200 ng mL−1. This study provides a rapid and low-cost approach for detecting proteins in blood, showing great promise for clinical application and biomedical diagnosis, particularly in limited resource settings. Combining the superpara-magnetism of Fe3O4 nanoparticles and the outstanding mechanical properties of carbon nanotubes, magnetized carbon nanotube-based lateral flow strip biosensor was first used for visual detection of proteins directly in whole blood avoiding complex purification and sample pretreatment. [Display omitted] •Magnetized carbon nanotube is first used as an immunochromatographic label.•Visual detection of protein in whole blood avoiding complex purification and sample-pretreatment.•The method is rapid, simple, low-cost and portable.