Layer-by-layer scaffold formation using magnetic attraction between HiPCO® single-walled carbon nanotubes and magnetic nanoparticles: Application for high performance immunosensors

Iron particle impurities of HiPCO® single-walled carbon nanotubes (SWCNTs) are treated as undesirable moieties and considerable times and efforts is allocated towards research and development to reduce their amount in HiPCO® SWCNTs. Taking advantage of this impurity, 3D nanostructured scaffolds are built via layer by layer (LBL) deposition of HiPCO® SWCNTs and magnetic nanoparticles which are retained via magnetic interaction with the iron particle impurities during the scaffold formation. The resulting scaffold has an inhomogeneous structure with large vacancies that can further be reinforced by electrogeneration of a functional polymer film to enable the immobilization of bioreceptor units for biosensing. Magnetic nanoparticles of different sizes are used to adjust the pore sizes within the scaffolds in order to determine the optimal particle size for their application as highly sensitive immunosensors. Scaffolds made of the magnetic nanoparticles with in average 500 nm sizes led to a sensitivity of 88 μA μg−1 mL cm−2 equivalent to a detection limit of 10 ng mL−1 for cholera antitoxin. This is by far the highest sensitivity for anti-CT immunosensors compared to amperometric transduction or ELISA.