Electroanalysis was performed using a boron-doped diamond (BDD) electrode for the simultaneous detection of 2-heptyl-3-hydroxy-4-quinolone (PQS), 2-heptyl-4-hydroxyquinoline (HHQ) and pyocyanin (PYO). PQS and its precursor HHQ are two important signal molecules produced by Pseudomonas aeruginosa, while PYO is a redox active toxin involved in virulence and pathogenesis. This Gram-negative and opportunistic human pathogen is associated with a hospital-acquired infection particularly in patients with compromised immunity and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. Early detection is crucial in the clinical management of this pathogen, with established infections entering a biofilm lifestyle that is refractory to conventional antibiotic therapies. Herein, a detection procedure was optimized and proven for the simultaneous detection of PYO, HHQ and PQS in standard mixtures, biological samples, and P. aeruginosa spiked CF sputum samples with remarkable sensitivity, down to nanomolar levels. Differential pulse voltammetry (DPV) scans were also applicable for monitoring the production of PYO, HHQ and PQS in P. aeruginosa PA14 over 8 h of cultivation. The simultaneous detection of these three compounds represents a molecular signature specific to this pathogen.

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N-Acetyltyramine was synthesized and electropolymerized together with a negatively charged sulfobutylether-β-cyclodextrin on a boron-doped diamond (BDD) electrode followed by the electropolymerization of pyrrole to form a stable and permselective film for selective dopamine detection. The selectivity and sensitivity of the formed layer-by-layer film was governed by the sequence of deposition and the applied potential. Raman results showed a decrease in the peak intensity at 1329 cm−1 (sp3), the main feature of BDD, upon each electrodeposition step. Such a decrease was correlated well with the change of the charge-transfer resistance derived from impedance data, i.e., reflecting the formation of the layer-by-layer film. The polycrystalline BDD surface became more even with lower surface roughness as revealed by scanning electron and atomic force microscopy. The modified BDD electrode exhibited rapid response to dopamine within 1.5−2 s and a low detection limit of 4−5 nM with excellent reproducibility. Electroactive interferences caused by 4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, ascorbic acid, and uric acid were completely eliminated, whereas the signal response of epinephrine and norepinephrine was significantly suppressed by the permselective film.

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Glucose oxidase (GO) was entrapped in an electrodeposited poly(tyramine) film together with a negatively charged sulfobutylether--cyclodextrin (SBCD) on the active area of a platinum (Pt) nanoparticle modified boron-doped diamond (BDD) electrode. Electrodeposition of tyramine and simultaneous entrapment of GO/ SBCD were performed in 50 mM phosphate buffer, pH 7 containing 0.1 M tyramine, 1750 units GO, and 10 mM SBCD. Atomic force microscopy (AFM) imaging revealed the presence of semicircular nanofibers with a height of 40 nm and an averaged length of 795 nm throughout the electropolymerized film surface. The combined film of poly(tyramine) and SBCD served as an excellent matrix polymer for the GO immobilization with high stability, selectivity, and reproducibility. Sensitive and selective detection of H 2 O 2 was realized at +0.4 V vs 3 M Ag/AgCl, since the poly(tyramine)/SBCD film was capable of preventing the passage of electroactive uric and ascorbic acids to the electrode. The glucose biosensor exhibited a remarkably selective response to glucose with a detection limit of 10 µM, linearity up to 110 mM, and a response time of 2 s. Glutaraldehyde cross-linking of the film with entrapped GO completely eliminated electroactive interference caused by uric and ascorbic acids.

An effective and robust electrochemical approach has been developed for selective detection of dopamine in the presence of 3,4-dihydroxyphenylalanine (L-DOPA), ascorbic acid, uric acid and other dopamine metabolites. A 'layer-by-layer' film of tyramine and pyrrole-1-propionic acid (PPA) was formed by subsequent electropolymerization on a boron-doped diamond (BDD) electrode with an overall thickness of $33 nm as estimated by AFM. The formation of the electropolymerized homogeneous film was also confirmed by SEM and Raman spectroscopy. The modified BDD electrode exhibited rapid response to dopamine within 6 s and a detection limit of 50 nM with excellent reproducibility. The stable electropolymerized film was capable of excluding electroactive interference from 20 mM L-DOPA, 20 mM 3,4-dihydroxyphenylacetic acid (DOPAC), and ascorbic and uric acids at normal physiological conditions (100 mM each). The modified electrode could be used for several repeated analyses of dopamine at 5 mM, without noticeable surface fouling. A plausible mechanism for permselectivity was suggested and supported by pertinent experimental data.

Centrifugally driven micro-fluidic discs (-CDs) have attracted significant interest within the analytical science community over the last decade, primarily being focused on the potential of such platforms for performing parallel and/or multiplex biological assays and further application in biomedical diagnostics. More recently, -CD based 5 devices have also been applied to environmental analysis as platforms for multisample extraction and transportation, prior to off-disc analysis in the laboratory.Therefore, this review critically summarises recent developments with -CD platforms for sample extraction, preconcentration, fractionation and purification in bioanalytical and environmental applications. In addition to also summarising the 10 common methods employed in the fabrication of -CD platforms, as applications of -CDs in sample extraction are generally based on enclosed series of extraction phases/micro-columns, the preparation of these stationary phases in micro-fluidic channels embedded in -CDs is also discussed. 15 KeywordsCentrifugally driven micro-extraction, micro-fluidic discs (-CD), lab-on-a-disc, sample extraction, preconcentration, fractionation, purification, packed stationary phase, monolithic stationary phase, electrophoretic separations.

A sensitive and selective electrochemical method for the determination of dopamine using a combined electropolymerized permselective film of polytyramine and polypyrrole‐1‐propionic acid on a glassy carbon (GC) electrode was developed. The formation of a “layer‐by‐layer” film has allowed for selective detection of dopamine in the presence of 3,4‐dihydroxyphenylalanine (L‐DOPA), DOPAC, ascorbic acid, uric acid, epinephrine and norepinephrine. The modified electrodes exhibited a detection limit of 100 nM with linearity ranging from 5×10−6 to 5×10−5 M. No cleaning step was required during the course of repeated measurement.