Abstract Nowadays, a prompt and reliable diagnosis is one of the most critical measures for leprosy control. The current diagnostic is based on clinical exams by a health care professional, and it may not recognize early signs of the disease. Therefore, other leprosy diagnosis methods are needed that are sensitive, disease-specific, and easy to deliver to the end-user. This study describes the construction of an electrochemical DNA biosensor to detect PCR products of Mycobacterium leprae using methylene blue as an indicator of the hybridization. The capture probe was immobilized on the graphite electrode modified with poly(4-aminophenol). The electrode surface was morphologically characterized by atomic force microscopy. Linear voltammetry was used to monitor the concentration of methylene blue on the DNA biosensor, which indicated a limit detection of 1 x 10-10 mol/L. The biosensor showed selective when placed to hybridize with a non-complementary sequence. This study suggests that the electrochemical DNA biosensor developed is promising for detecting DNA of Mycobacterium leprae.

ABSTRACT Strongyloidiasis is a helminthiasis of neglected condition that has no gold standard parasitological diagnosis due to the intermittent release of larvae in feces. This study aimed to use an scFv (single chain variable fragment) obtained by Phage Display, previously validated to detect immune complexes in serum samples from individuals infected with Strongyloides stercoralis by enzyme-linked immunosorbent assay (ELISA). Now the ability of scFv to detect the immune complexes was verified by immunofluorescence, flow cytometry using magnetic beads and surface plasmon resonance (SPR). As ELISA, the SPR, immunofluorescence and flow cytometry demonstrated the ability of scFv to detect immune complexes in sera from individuals with strongyloidiasis and discriminate them from sera of individuals with other parasitic diseases and healthy individuals. Besides de conventional ELISA, the novel approaches can also be promptly applied as auxiliary diagnostic tools to the existing parasitological method for accurate diagnosis of human strongyloidiasis.

The properties of poly(4-aminophenol) modified graphite electrode as material for the immobilization of acetylcholinesterase were investigated by the Cyclic Voltammetry, Electrochemical Impedance Spectroscopy and Atomic Force Microscopy. The polymer was deposited on graphite electrode surface by the oxidation of 4-aminophenol and then acetylcholinesterase was immobilized on the surface of the electrode. The biosensor coupled in the continuous flow system was employed for the detection of dichlorvos. The detection and quantification limits were 0.8 and 2.4 μmol L-1 dichlorvos, respectively. Graphite electrodes modified with the poly(4-aminophenol) showed to be an efficient and promising material for immobilization of acetylcholinesterase enzyme. The proposed method requires simple parts which are easy to build, involves only one biosensor and the potentiometric detection is simple.