Imunossensores eletroquímicos para a detecção da proteína rica em histidina 2 do Plasmodium falciparum

Two distinct methods for fabricating disposable label-free electrochemical immunosensors for the detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) are reported in this work. For this purpose, screen-printed gold electrodes (SPAuE) (DropSens) were used as a substrate for the sensors. In the first method, the electrodes were modified with a dispersion of multiwall carbon nanotubes (MWCNTs) in dihexadecylphosphate (DHP). The MWCNTs were previously functionalized covalently with polyclonal antibodies using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/Nhydroxysuccinimide (EDC/NHS) as coupling agents. In the second method, immunossensor was prepared in absence of carbon nanotubes, i.e., the electrode surface was modified with only DHP and the antibodies. Cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM) were used for the characterization of the uniform and stable films deposited on the electrode surface. Figure 1a shows CVs recorded with all prepared electrodes. The increase in current observed for the DHP/MWCNTs electrode, when compared to the modified electrode containing only DHP (Fig 1a), indicates that the use of functionalized MWCNTs facilitates the electron transfer process involving both electroactive species. The comparison between the two modification strategies for the developed immunosensors was performed by SECM employing a 4.3 µm radius Platinum microelectrode as a tip. The SPAuE substrate was modified on four distinct sites with 1 µL of solutions containing different materials: DHP/MWCNT/PfHRP2, DHP/PfHRP2, DHP/MWCNTs and DHP (Figure 1b). Electrochemical images were acquired using feedback mode before and after exposing the modified electrode to the antigen solution for 30 min. Normalized tip current values (by the pre-exposure data, point by point) were lower in the spots containing antibodies, demonstrating the bioactivity of antibodies after immobilization and the interaction with the antigen.