Sensor based on redox conjugated poly(para-phenylene) for the simultaneous detection of dopamine, ascorbic acid, and uric acid in human serum sample.

An electrochemical sensor for the individual and the simultaneous detection of dopamine (DA), ascorbic acid (AA), and uric acid (UA) based on redox conjugated "poly(para-phenylene)" (Fc-ac-PPP) bearing ferrocene and carboxylic acid in lateral position has been developed. The electrochemical characterization of the sensor has been studied with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA). We highlighted that the catalytic activity of the Fc-ac-PPP polymer provided by its redox electrochemical properties and chemical structure allows the electrochemical detection of DA, AA, and UA. We demonstrated that the sensor provides high sensitivity and selective signal in the coexistence of DA, AA, and UA within a short time. Low detection limits and wide linear ranges of detection have been demonstrated respectively for DA 3 × 10-10 M (1 nM-10 µM), AA 1.6 × 10-8 M (0.1 µM-1 mM), and UA 1 × 10-8 M (0.1 µM-1 mM). In addition, the sensor has been successfully applied to determine DA in urine and human serum samples even in the presence of high concentrations of AA and UA. This sensor could be a powerful device for the detection of other electroactive compounds thanks to its high catalytic properties and chemical structure. Graphical abstract.

Direct E-DNA sensor of Mycobacterium tuberculosis mutant strain based on new nanocomposite transducer (Fc-ac-OMPA/MWCNTs).

Direct DNA sensor based on new nanocomposite materials (Fc-ac-OMPA/MWCNTs) has been investigated. This nanocomposite was formed by combining the redox oligomer "oligo-methoxy-phenyl-acetonitrile" (Fc-ac-OMPA) and the MWCNTs via a simple π-π stacking interaction in the aim to ameliorate the biosensor performance. The redox indicator and the functional groups of the redox oligomer have been used for monitoring the electrochemical behavior and the flexibility for direct covalent attachment of Hepatitis C DNA probe. This nanocomposite shows high performance of DNA hybridization with a detection limit of 0.08 fmol L-1. Moreover, the biosensor was applied for the detection of pathogenic bacterium such as DNA from Mycobacterium tuberculosis strand. Developed biosensor has been able to detect a single nucleotide polymorphism (SNP)T (TCG/ TTG) which confers resistance of M. tuberculosis to rifampicin drug.

Direct Electrochemical DNA Sensor based on a new redox oligomer modified with ferrocene and carboxylic acid: Application to the detection of Mycobacterium tuberculosis mutant strain.

A new redox oligomer "oligo-methoxy-phenyl-acetonitrile" (Fc-acid-OMPA) modified with ferrocene groups and carboxylic acids as functional groups in side chains, has been synthesized. The redox indicator has been used for monitoring the electrochemical behavior. The functional groups give the flexibility for direct covalent attachment of biomolecules. The electrochemical properties of the redox oligomer film deposited on gold electrodes have been studied by cyclic voltammetry (CV), which showed a rate of electron transfer of 6.43 s-1. The oligomer has been studied as a transducer for electrochemical DNA sensing and for this purpose the acid functional group of Fc-acid-OMPA was attached with the DNA probe of hepatitis C bearing amino group in 5' position through amid link. The efficiency of DNA attachment on the oligomer film has been analyzed by X-Ray Photoelectron Spectrometry (XPS) and FT-IR spectroscopy. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been used to analyze the biosensor construction and DNA detection. A wide linear range of detection from 1 fM to 100 pM have been demonstrated with a limit of detection (LOD) of 0.2 fM. The biosensor has showed an appreciated sensitivity to PCR samples of genomic DNA from Mycobacterium tuberculosis, and has been able to detect a single mutation which confers resistance of M. tuberculosis to rifampicin drug.