Determination of Morphine Using Carboxylated Multiwalled Carbon Nanotubes (MWCNTs) as the Label for an Immunochromatographic Assay (ICA)

This study evaluated the application of carboxylated multi-walled carbon nanotubes (MWCNTs) as a label in immunochromatographic assay for morphine detection. MWCNTs were carboxylated using nitric acid and characterized by Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, field emission scanning microscopy (FESEM), and dynamic light scattering (DLS). The optimum concentration of polyvinyl pyrrolidone (PVP) as a surfactant for homogenous dispersion of MWCNTs was determined by ultraviolet-visible spectroscopy to be 0.5 mg/mL. The zeta potential of MWCNTs before adding PVP was −41.9 ± 1.02 mV, and after adding PVP, −54.1 ± 0.25 mV. On the surface of MWCNTs, the anti-morphine antibody (AM antibody) had a binding effectiveness ranging from 91.1% to 95.5%. The AM antibody-MWCNTs were conjugated to create immunochromatographic test strips. The visual limit of detection (vLOD) was 1.0 ng/mL and the cutoff concentration (COC) was 10.0 ng/mL. Compared to previous study, carboxylated-MWCNTs as a one-dimensional nanomaterial improved the sensitivity of immunochromatographic assay strips and may be utilized to develop the sensitive immunochromatographic assays.