Chronocoulometric signalling of BNP using a novel quantum dot aptasensor.

This study is a first-time report of the development of a mercaptosuccinic acid-nickel selenide quantum dots (MSA-NiSe2 QDs)-based electrochemical aptasensor for brain natriuretic peptide (BNP) detection. Herein, novel MSA-NiSe2 QDs were synthesized by microwave irradiation. Microscopic and structural analysis revealed that the QDs are spherical with an average diameter of 2 nm. In the presence of the as-prepared QDs, an amine-modified DNA aptamer sequence was attached to a disposable sensing interface through 1-ethyl-3-(3-dimenthylaminopropyl) carbodiimide/N-hydroxysuccinimide coupling chemistries. Electroanalytical analysis revealed that the developed QDs-based electrochemical aptasensor is highly selective towards BNP and successfully detected BNP in both physiological buffer and human plasma samples with detection limits of 5.45 pg mL-1 and 31.95 pg mL-1, respectively. Moreover, the results revealed a 3-fold enhancement in the loading capacity of the BNP aptamer in the presence of MSA-NiSe2 QDs. By taking advantage of the physical and electronic properties of the novel QDs these materials can be easily adapted to other diagnostic approaches.

Electrochemiluminescence at 3D Printed Titanium Electrodes.

The fabrication and electrochemical properties of a 3D printed titanium electrode array are described. The array comprises 25 round cylinders (0.015 cm radius, 0.3 cm high) that are evenly separated on a 0.48 × 0.48 cm square porous base (total geometric area of 1.32 cm2). The electrochemically active surface area consists of fused titanium particles and exhibits a large roughness factor ≈17. In acidic, oxygenated solution, the available potential window is from ~-0.3 to +1.2 V. The voltammetric response of ferrocyanide is quasi-reversible arising from slow heterogeneous electron transfer due to the presence of a native/oxidatively formed oxide. Unlike other metal electrodes, both [Ru(bpy)3]1+ and [Ru(bpy)3]3+ can be created in aqueous solutions which enables electrochemiluminescence to be generated by an annihilation mechanism. Depositing a thin gold layer significantly increases the standard heterogeneous electron transfer rate constant, ko, by a factor of ~80 to a value of 8.0 ± 0.4 × 10-3 cm s-1 and the voltammetry of ferrocyanide becomes reversible. The titanium and gold coated arrays generate electrochemiluminescence using tri-propyl amine as a co-reactant. However, the intensity of the gold-coated array is between 30 (high scan rate) and 100-fold (slow scan rates) higher at the gold coated arrays. Moreover, while the voltammetry of the luminophore is dominated by semi-infinite linear diffusion, the ECL response is significantly influenced by radial diffusion to the individual microcylinders of the array.

Wireless electrochemiluminescence at functionalised gold microparticles using 3D titanium electrode arrays.

Wireless electrochemiluminescence is generated using interdigitated, 3D printed, titanium arrays as feeder electrodes to shape the electric field. Gold microparticles (45 µm diameter), functionalised with 11-mercaptoundecanoic acid, act as micro-emitters to generate electrochemiluminescence from [Ru(bpy)3]2+, (bpy is 2,2'-bipyridine) where the co-reactant is tripropylamine. The oxide coated titanium allows intense electric fields, whose distribution depends on the geometry of the array, to be created in the absence of deliberately added electrolyte. COMSOL modelling and long exposure ECL imaging have been used to map the electric field distribution. Significantly, we demonstrate that by controlling the surface charge of the gold microparticles through the solution pH, the light intensity can be increased by a factor of more than 10.

Wireless Electrochemiluminescence at Nafion-Carbon Microparticle Composite Films.

Thin films of a composite of nafion and carbon microparticles have been deposited on nonconducting substrates and their conductivity as well as their ability to generate electrochemiluminescence investigated. The films exhibit very low conductivity (<6 × 103 S m-1) for low particle loadings, but once the percolation threshold is reached (volume percentage of 71 ± 8% carbon particles), the conductivity increases dramatically and a maximum conductivity of 2.0 ± 0.1 × 107 S m-1 is achieved. The electrochemical properties of the composites, including heterogeneous electron transfer rates, were probed using cyclic voltammetry. Significantly, bipolar, or wireless, electrochemiluminescence can be generated with films that contain >65% (by volume) carbon particles using [Ru(bpy)3]2+ as the luminophore and tripropylamine as the coreactant, at an electric field of 14 V cm-1. Under these conditions, the complete film is sufficiently conducting to become polarized in the external electric field and the electrochemiluminescence intensity correlates strongly with the film conductivity. These results demonstrate the usefulness of particle arrays for the wireless generation of electrochemiluminescence at relatively low electric field strengths.