Electrochemical Biosensor for Sensitive Detection of Hepatitis B in Human Plasma.

In this work, we report the construction of a novel electrochemical device for molecular diagnosis of hepatitis B virus in the blood plasma of infected patients, using graphite electrodes functionalized with poly(4-aminophenol) and sensitized with a specific DNA probe. The recognition of genomic DNA was evaluated by electrochemical techniques (DPV and EIS) and scanning electron microscopy. The genosensor was efficient in detecting genomic DNA with a linear range from 1.176 to 4.825 µg mL-1 and detection limit of 35.69 ng mL-1 (4.63 IU ml-1 or 25.93 copies.ml-1), which is better than the 10.00 IU ml-1 limit of reference method, real-time PCR, used in point of care. EIS analysis shows that the genosensor resistance increased exponentially with the concentration of the genomic DNA target. This novel platform has advantages to its applicability in real samples, such as good sensitivity, selectivity, low sample volume, and fast assay time (36 min), thus interesting for application in the diagnosis of hepatitis B virus in blood plasma. Also, the ease of synthesis of the low-cost polymer by electrosynthesis directly on the electrode surface allows the translation of the platform to portable devices.

Innovative approaches to improve serodiagnosis of Strongyloides stercoralis infection.

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.

Electrochemical DNA Biosensor for Mycobacterium leprae Identification

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.

Serological Electrodetection of Rheumatoid Arthritis Using Mimetic Peptide.

BACKGROUND: Rheumatoid arthritis is the most common inflammatory autoimmune disease in the world. Recently new targets for its detection were developed as alternatives to classic biomarkers, including the M-12 peptide, that mimics carbonic anhydrase III. Thus, the application of this peptide for the development of new detection devices is attractive. OBJECTIVE: Our goal was to construct a modified electrode for immobilization of M-12 peptide and detection of a rheumatoid arthritis biomarker in serum of patients. METHODS: 3-Hydroxybenzoic acid was electropolymerized onto graphite electrodes, and M-12 peptide was immobilized by adsorption. Negative and positive serum samples for rheumatoid arthritis were diluted and applied onto the electrode. Detection was carried in potassium ferrocyanide/ ferricyanide solution by differential pulse voltammetry. Atomic force microscopy and scanning electron microscopy were used to evaluate electrode surfaces. RESULTS: Cyclic voltammograms indicated the poly(3-hydroxybenzoic acid) formation and increase of electroactive area. Immobilization of M-12 probe increased current by 1.2 times, and negative serum addition caused no suitable difference. However, positive serum showed expressive decrease in the current signal of about 2.2 times, possibly due to steric hindrance when the anti-CA3 antibody interacts with the M-12 peptide, decreasing the electron transfer. Microscopies images corroborated with the electrochemical detection, showing evident changes in the morphology of the electrode surfaces. CONCLUSION: The bioelectrode was able to discriminate positive and negative serum samples of rheumatoid arthritis by a considerable decrease in the current signal value. Morphological analyses supported the electrochemical results. Thus, the constructed bioelectrode offers a new platform for detection of rheumatoid arthritis.

Molecular modeling study on the possible polymers formed during the electropolymerization of 3-hydroxyphenylacetic acid.

The compound 3-hydroxyphenylacetic acid (3-HPA) has been used as a monomer in the synthesis of polymeric films by electropolymerization; these films serve as supports for the immobilization of biomolecules in electrochemical biosensors. To assist in the elucidation of the mechanism of 3-HPA electropolymerization, a systematic quantum mechanical study was conducted. In addition to the monomer, all possible intermediates and the probable oligomers formed during the electropolymerization were investigated using a density functional theory (DFT) method combined with a previous conformational analysis performed with the aid of the RM1 semi-empirical method or a Monte Carlo conformational analysis with the force field OPLS-2005. From the data analysis combined with the experimental results, a mechanism was proposed for the main route of formation of the polymeric films. The mechanism involves the formation of polyethers from the coupling of phenoxide radicals and radicals based on the aromatic ring.

A Biosensor Using Poly(4-Aminophenol)/acetylcholinesterase modified graphite electrode for the detection of dichlorvos

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.

Recent advances in nano-based electrochemical biosensors: application in diagnosis and monitoring of diseases.

Based on biological molecules combined with nanostructured components, the news generations of electrochemical biosensors can employ different transducers (potentiometric, amperometric and impedimetric) converting the chemical information into a measurable amperometric signal. Following this contemporary theme, our main focus in this review is to discuss different methodologies for application in biosensing, whose signal transduction is based on electrochemical principles. We apply a discussion on recent trends involving different nanostructured materials, but without daring to contemplate all nanomaterials incessantly cited in literature, which leads us to believe that this moment is an unprecedented revolution in the preparation of electrochemical biodevices. Besides, some structures of bio-nano interface and different electrochemical biosensors involved in diagnosis systems are also discussed. We outline in several parts of the report how nanoscience technologies are emerging in diagnostic medicine, as well as convergence of electrochemistry and bio-nanoscience. Our hopes for this review are that it can help different categories of researchers to understand the broad application area of electrochemistry and bioelectrochemistry, in order to detecting several types of diseases and biological phenomena.