Microfluidic device based on electrodeposited Nanoporous Gold/Carbon Nanotubes for Plasmodium vivax detection

A portable microfluidic electrochemical immunosensor for Plasmodium vivax antibodies determination was developed. A gold microelectrode placed inside the central channel of the microfluidic device was used as immobilization platform for a specific fragment (19-kDa) derived from the P. vivax merozoite surface protein 1, known as PvMSP119. The gold microelectrode surface was modified by using a dynamic hydrogen bubble template (DHBT) method in the presence of multiwalled carbon nanotubes. The synthesized nanocomposite presented exceptional properties, like high specific surface area, remarkable biocompatibility, and excellent electrochemical activity. The material was characterized by scanning electron microscopy, energy dispersive spectrometry, x-ray diffraction, and cyclic voltammetry. The antibodies (anti-PvMSP119) present in the sample bind to the PvMSP119 immobilized on the microelectrode surface, which is then labeled with an anti-IgG antibody marked with horseradish peroxidase (HRP-antiIgG). Finally, the substrate solution (H2O2 + catechol) is added, and the enzymatic product (quinone) is reduced on the NPAu electrode at +0.2 V (vs. Ag/AgCl). The current obtained is directly proportional to the antiPvMSP119 concentration in the sample. The detection limit of the microfluidic electrochemical immunosensor was 0.6 ng mL-1, much lower compared to the ELISA detection limit of 15 ng mL-1. This is the first microfluidic electrochemical immunosensor device suitable for point-of-care determination of anti-PvMSP119 in human serum samples. (AU)