Wireless Electrochemiluminescence at Nafion–Carbon Microparticle Composite Films

Wireless rotating bipolar electrochemiluminescence for enzymatic detection

New dynamic, wireless and cost-effective analytical devices are developing rapidly in biochemical analysis. Here, we report on a remotely-controlled rotating electrochemiluminescence (ECL) sensing system for enzymatic detection of a model analyte, glucose, on both polarized sides of an iron wire acting as a bipolar electrode. The iron wire is controlled by double contactless mode, involving remote electric field polarization, and magnetic field-induced rotational motion. The former triggers the interfacial polarization of both extremities of the wire by bipolar electrochemistry, which generates ECL emission of the luminol derivative (L-012) with the enzymatically produced hydrogen peroxide in presence of glucose, at both anodic and cathodic poles, simultaneously. The latter generates a convective flow, leading to an increase in mass transfer and amplifying the corresponding ECL signals. Quantitative glucose detection in human serum samples is achieved. The ECL signals were found to be a linear function of the glucose concentration within the range of 10-1000 μM and with a limit of detection of 10 μM. The dynamic bipolar ECL system simultaneously generates light emissions at both anodic and cathodic poles for glucose detection, which can be further applied to biosensing and imaging in autonomous devices.

Site-selective heat boosting electrochemiluminescence for single cell imaging

In operando visualization of local electrochemical reactions provides mechanical insights into the dynamic transport of interfacial charge and reactant/product. Electrochemiluminescence is a crossover technique that quantitatively determines Faraday current and mass transport in a straightforward manner. However, the sensitivity is hindered by the low collision efficiency of radicals and side reactions at high voltage. Here, we report a site-selective heat boosting electrochemiluminescence microscopy. By generating a micron-scale heat point in situ at the electrode-solution interface, we achieved an enhancement of luminescence intensity up to 63 times, along with an advance of 0.2 V in applied voltage. Experimental results and finite element simulation demonstrate that the fundamental reasons are accelerated reaction rate and thermal convection via a photothermal effect. The concentrated electrochemiluminescence not only boosts the contrast of single cells by 20.54 times but also enables the site-selective cell-by-cell analysis of the heterogeneous membrane protein abundance. This electrochemical visualization method has great potential in the highly sensitive and selective analysis of local electron transfer events.

Sensitive electrochemiluminescence biosensing of polynucleotide kinase using the versatility of two-dimensional Ti3C2TX MXene nanomaterials

Electrochemiluminescence (ECL) is a powerful readout method for the development of (bio)sensors, whose performances depend on the electrode materials and the architecture of its surface. Herein, we demonstrate that the precise control of the sensing interface using the versatility of two-dimensional (2D) transition metal carbides (Ti₃C₂T_X MXene) leads to the enhancement of the ECL signal. This electrode material, which exhibits remarkable structural and electrochemical properties was decorated by the in situ formation of gold nanoparticles (AuNPs) owing to the Ti reducibility. Then, a large amount of the luminophore, Ru(bpy)₃²⁺, was immobilized on Ti₃C₂T_X MXene thanks to its unique negative charge and large specific surface area to obtain Ru-Ti₃C₂T_X-AuNPs. The presented approach exploits the high catalytic activity and excellent conductivity of this 2D nanomaterial as illustrated by the enhanced ECL emission performance of the Ru-Ti₃C₂T_X-AuNPs nanoprobes. Finally, DNA phosphorylated with polynucleotide kinase (PNK) was recognized efficiently by the chelation between Ti and phosphate group. A highly sensitive and selective ECL biosensor was developed for the detection of PNK and the screening of its inhibitors. A lower detection limit of 0.0002 U mL^-1 and wide linear relationship ranged from 0.002 to 10 U mL^-1 were obtained. Furthermore, the practicality of our method was tested in MCF-7 cell lysate, which opens enticing perspectives for future applications of Ti₃C₂T_X materials in the ECL bioanalysis field.

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.

Mimic peroxidase-transfer enhancement of photoelectrochemical aptasensing via CuO nanoflowers functionalized lab-on-paper device with a controllable fluid separator

Inspired by the design of folding greeting cards and tissue drawing covers, a photoelectrochemical (PEC) lab-on-paper device with a controllable fluid separator, producing both reaction zone and detection zone, was explored for ultrasensitive detection of adenosine 5'-triphosphate (ATP) via mimic peroxidase-transfer enhancement of photocurrent response. To realize it, the DNA1, aptamer, and DNA2 as well as the mimic peroxidase of G-quadruplex/hemin modified Au nanocubes were linked on the graphene oxide-functionalized reaction zone via the DNA hybridization. Meanwhile, three-dimensional CuO nanoflowers (CuO NFs) as a photoactive material with outstanding electron transfer ability and absorption of light were grown in situ on the detection zone, providing a PEC active interface. Besides, an innovative fluid separator was elaborately designed by assembling a strip of paper with a hydrophilic channel, providing an effective way to bridge the gap between the two zones with a controllable drawing way, which could successfully avoid the signal interference caused by modifying biomolecules layer by layer on photosensitive materials. In the presence of ATP, the G-quadruplex/hemin modified in the reaction zone was dissociated due to the specific recognition of ATP with aptamer and released into the detection zone with the assistance of controllable fluid separator. The free G-quadruplex/hemin could catalyze hydrogen peroxide to generate oxygen for the consumption of photo-induced electrons from CuO NFs, which could further promote the electron-hole carriers separation efficiency, and eventually resulting in the enhancement of PEC signal. The proposed PEC lab-on-paper device could be employed for specific detection of ATP in the range from 5.0 to 3.0 × 10³ nM with a detection limit of 2.1 nM.