Surface properties of sensors based on aminophenol-polymerized film

In this work, carbon electrodes modified with aminophenols were developed for the production of pesticides biosensors based on acetylcholinesterase. The polymers were potentiodynamically deposited on a graphite electrode surface by the oxidation of monomers, 2-aminophenol, 3-aminophenol and 4-aminophenol. The electrochemical behaviour and surface analysis of the electrodes modified by polyaminophenols non-immobilized and immobilized on acetylcholinesterase were studied by cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy. Roughness values obtained for graphite electrodes modified with poly(4-aminophenol) and poly(4-aminophenol)/acetylcholinesterase were 174 and 86 nm, respectively. The acetylcholinesterase enzyme was immobilized on a graphite and a graphite modified with poly(4-aminophenol), and these electrodes were coupled in the flow system. Potentiometric response due to hydrogen ions generated by an enzymatic system in the presence of acetylcholine chloride substrate was evaluated. The results showed that the graphite/poly(4-aminhophenol) sensor presents high sensitivity to hydrogen ions when compared with other graphite/polyaminophenols sensors. The biosensor coupled in a 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. This sensor reveals an efficient and promising material for biomolecules immobilization.     

Modified electrode with reduced graphene oxide/poly(3-hydroxyphenylacetic acid): a new platform for oligonucleotide hybridization

Journal of Solid State Electrochemistry - This paper reports a new platform for oligonucleotide hybridization, prepared by electropolymerization of 3-hydroxyphenylacetic acid onto gold electrode...     

Immunosensor for electrodetection of the C-reactive protein in serum

Epidemiological studies have demonstrated an association between the risk of cardiovascular events and increasing C-reactive protein (CRP) concentration. This paper reports the development of an immunosensor for the assessment of the cardiovascular process using anti-C-reactive protein antibody immobilized onto a gold-printed screen electrode. Positive and negative human sera were successfully evaluated using electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and atomic force microscopy (AFM). EIS results show that, after the incubation with positive serum for myocardial infarction, the resistance increased about two times in relation to the negative serum. A linear range from 6.25 to 50 μg mL^?1 and detection limit of 0.78 μg mL^?1 using DPV were obtained. The immunosensor developed for the CRP detection using gold electrode revealed efficacy and a potential use for the diagnosis and monitoring of the progression of cardiovascular diseases.     

A new genosensor for meningococcal meningitis diagnosis using biological samples

In this work, a new electrochemical biosensor for DNA detection of bacterial meningitis is proposed. The system is based on specific DNA fragments from the Neisseria meningitidis genome as a probe incorporated on graphite electrodes modified with poly(4-aminophenol). Detection of a complementary oligonucleotide sequence, a specific 710-base pair amplicon, and the genomic DNA of bacteria was carried out by differential pulse voltammetry, using ethidium bromide as an electroactive indicator of hybridization. The complementary oligonucleotide and the genomic DNA of Neisseria meningitidis were quantified by the genosensor, showing detection limits of 0.6 ng μL^?1 and about 6 ng μL^?1, respectively. Morphological differences were observed between hybridized and unhybridized surfaces by atomic force microscopy. The biosensor showed high selectivity, discriminating non-specific targets, and high stability retaining over 98% of its original activity after 120 days of storage. The bioelectrode was effective in discriminating the genomic DNA in samples with human serum without significant interference, proving to be an interesting platform for meningococcal meningitis diagnosis.     

A Novel and Reusable Electrochemical Genosensor for Detection of Beef Adulteration

This work describes the construction of a genosensor based on a graphite electrode modified with an reduced graphene oxide/poly(3-hidroxybenzoic acid) nanocomposite with an specific DNA oligonucleotide for detection of cattle mitochondrial DNA, in order to certify beef purity. Electrochemical and morphological analyses indicate that the genosensor allows duplex formation with the DNA of pure sample of beef lysate. The genosensor was selective, identifying up to 1 % (w/w) of pork in beef samples, showing good reproducibility and stability within six weeks of storage, and can be reused four times, being a great tool for the evaluation of beef purity, with application in the meat production and marketing chain.     

Novel electrochemical platform based on copolymer poly(aniline-4-aminophenol) for application in immunosensor for thyroid hormones

Journal of Solid State Electrochemistry - This paper reports the development of a novel electrochemical platform based on graphite electrodes modified with copolymer poly(aniline-4-aminophenol) and...     

Development of a mimetic system for electrochemical detection of glutamate

This paper describes the development of a biosensor to detect neurodegenerative diseases, focusing on Alzheimer’s disease, the most common type of dementia, based on the use of a small protein-like chain designed to mimic a peptide that recognizes glutamate, the main excitatory neurotransmitter present in the central nervous system of mammals. This system is based on the immobilization of the mimetic peptide for glutamate onto graphite electrodes. The produced bioelectrode showed interesting characteristics, such as short response time (about 10 s) and linear response range between 1 and 10 mmol L^?1 for glutamate, indicating a promising approach for the diagnosis of neurological diseases. In addition, it was possible to observe differences in charge transfer resistance and in surface topography of the electrode, after the interaction with the glutamate target. Theoretical calculations suggest that the anchoring of glutamate indicates conformational changes in the peptide. The mimetic bioelectrode discriminates samples from patients with Alzheimer’s disease.     

Development of electrochemical genosensor for MYCN oncogene detection using rhodamine B as electroactive label

A novel electrochemical genosensor based on a graphite electrode modified with poly(4-aminophenol) has been constructed for prognostic of neuroblastoma, a malignant tumor originating from embryonic precursor cells of the sympathetic nervous system and associated with the amplification of the MYCN oncogene. The genosensor exhibited distinct electrical and morphological properties using rhodamine B as indicator of DNA hybridization. The detection limit was evaluated to be 0.47 μmol L^?1 (n = 3), and the electrochemical genosensor was selective for the complementary DNA, using serum sample. This DNA sensing platform was successfully applied to detect MYCN, an important biomarker for neuroblastoma.     

Electrochemical Detection of Zika Virus in Biological Samples: A Step for Diagnosis Point‐of‐care

This work describes an electrochemical genosensor for detection of genomic RNA of Zika virus in real samples of infected patients, using a new platform based on graphite electrodes modified with electrochemically reduced graphene oxide and polytyramine‐conducting polymer. The developed genosensor was suitable for differentiation between samples of healthy and infected patients with Zika virus by differential pulse voltammetry, detecting up to 0.1 fg/mL (1.72 copies/mL), showing good stability (about 60 days), rapid analysis (about 20 min) and potential for filling the lack of practical diagnostic methods for Zika virus.