Application of nanomaterials for the electrical and optical detection of the hepatitis B virus.

This work describes different approaches for the detection of hepatitis B virus (HBV) genomic DNA, using electrochemical and optical techniques. The platforms consisted of a single-stranded DNA probe (HEPB1S), specific to HBV, grafted on a gold electrode modified with reduced graphene oxide or gold nanoparticles. Differential pulse voltammetry analysis indicates that the addition of HBV genomic DNA caused an increase of about 1.4 times in the current peak value, when compared to the negative control. It was observed a linear dependence with the log HBV-genomic DNA concentration and the electrochemical biosensor detected until 7.65 pg µL-1 of the target. Electrochemical impedance spectroscopy measurements showed an increase of about 2 times in the charge transfer resistance, after the addition of HBV genomic DNA. Assays using colloidal suspension of gold nanoparticles showed a shift of the peak wavelength, linearly proportional to the HBV-genomic DNA concentration, with a detection limit of 0.15 ng µL-1. The applicability of the gold nanoparticles for clinical samples was tested with success in the blood plasma. All the approaches used in this work were effective in detecting genomic DNA or blood plasma in positive samples for HBV.

Development of a label-free immunosensor based on surface plasmon resonance technique for the detection of anti-Leishmania infantum antibodies in canine serum.

In this work, a surface plasmon resonance (SPR) immunosensor was developed using an 11-mercaptoundecanoic acid (11-MUA) modified gold SPR sensor chip for the detection of anti-Leishmania infantum antibodies. The soluble antigens of L. infantum were securely immobilized on an SPR gold disk by an 11-MUA self-assembled monolayer. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) techniques were employed in the characterization of the antigen immobilization. After the immunosensor construction, canine serum positive for visceral leishmaniasis was added to its surface and showed significant variation in the SPR angle, indicating excellent sensitivity of the technique for antigen-antibody interaction detection. Moreover, the addition of negative serum was accompanied by a smaller response, demonstrating that the immunosensor shows good specificity against anti-L. infantum antibodies. Therefore, this work demonstrates the successful development of an SPR sensor for anti-L. infantum antibodies detection in short time, showing a great perspective as a sensing system of visceral leishmaniasis in endemic regions.