Enhanced catalytic activity of gold nanoparticle-carbon nanotube hybrids for influenza virus detection

Multifunctional nanohybrids have created new and valuable opportunities for a wide range of catalysis and biotechnology applications. Here, we present a relatively simple method for producing nanohybrids composed of gold nanoparticles (Au NPs) and carbon nanotubes (CNTs) that does not require an acidic pre-treatment of the CNTs. Transmission electron microscopy (TEM) images and ultraviolet-visible (UV-vis) spectra revealed that Au NPs bonded to the CNT surface. Surface-enhanced Raman scattering (SERS) revealed a stronger signal from Au-CNT nanohybrids than from pristine CNTs. The Au-CNT nanohybrids showed catalytic activity in the oxidation of 3, 3', 5, 5'-tetramethyl-benzidine (TMB) by H2O2 and developed a unique blue colour in aqueous solution. Because of the enhanced peroxidase-like activity of these Au-CNT nanohybrids, they were selected for use as part of a highly sensitive colorimetric test for influenza virus A (H3N2). In the presence of influenza A virus (H3N2) in the test system (specific antibody-conjugated Au CNT nanohybrids-TMB-H2O2), a deep blue colour developed, the optical density of which was dependent on the virus concentration (10-50,000 PFU/ml). The limit of detection of this proposed method was 3.4 PFU/ml, a limit 385 times lower than that of conventional ELISA (1312 PFU/ml). The sensitivity of this test was also 500 times greater than that of commercial immunochromatography kits. The nanohybrid preparation and colorimetric detection methods reported herein may be easily adapted to other nanohybrid structures with enzyme mimetic properties for broader applications in catalysis and nanobiotechnology.