Fabrication of a highly efficient solid state electrochemiluminescence sensor using Ru(bpy)32+ incorporated nanoZnO-MWCNTs-Nafion composite film

An ultrasensitive solid-state electrochemiluminescence sensor based on Ni-MOF@Ru(bpy)32+ and Au NPs@TiO2 for determination of permethrin

The novel TiO2 and Ni-MOF materials were synthesized and utilized for the detection of permethrin (PET). A highly sensitive solid-state electrochemiluminescence (ECL) sensor was developed based on Ni-MOF@Ru(bpy)32+ and Au NPs@TiO2. In this sensing platform, Ru(bpy)32+-Tripropyl Amine (TPrA) was used as a luminescent signal, Ni-MOF acted as a carrier to carry more luminescent reagents Ru(bpy)32+. Au NPs acted as promoters facilitated electron transport and TiO2 could further enhance the luminescence intensity of the system by synergistical interaction with Au NPs. The possible mechanisms of signal amplification were investigated. The ECL intensity decreased significantly with increasing PET concentration, enabling the determination of PET amount through the observation of the change in ECL signal intensity (ΔI). Under optimal experimental conditions, the linear range of PET concentration from 1.0 × 10-11 mol L-1 to 1.0 × 10-6 mol L-1, with a detection limit of 3.3 × 10-12 mol L-1 (3S/N). This method was successfully applied to determine PET in various vegetable samples.

Novel nanocomposite of spiky-shaped gold nanourchins/ titanium dioxide/nafion for amplified signal and efficient electrochemiluminescence detection of ovomucoid

This work reports on the first electrochemiluminescence (ECL) immunosensor employing a novel nanostructured composite of titanium dioxide (TiO₂) and gold nanourchins (AuNU) to detect protein allergen Ovomucoid (Ovm) found in eggs. TiO₂ and AuNU were dispersed in Nafion and drop-casted onto SPGE with Tris(2,2'-bipyridyl)-ruthenium (II) ([Ru(bpy)₃]²⁺) and tri-n-propylamine (TPrA) served as strong luminophore/co-reactant pairs as a source of ECL signals. The linear range, limit of detection, reproducibility and practical applications of the sensor were assessed. The fabricated ECL immuosensor produced a promising limit of detection of as low as 0.01 pg/mL. Two linear ranges of 0.01-50 pg/mL and 100-750 pg/mL with corresponding correlation coefficients of R² = 0.99136 and R² = 0.97829) respectively, were determined. Despite its simple fabrication method, this label-free immunosensor also showcased excellent selectivity, reproducibility, interference-resistance and yielded outstanding recoveries between 97.42 and 104.05% of Ovm analysis in spiked real food samples.

A solid-state electrochemiluminescence aptasensor for β-lactoglobulin using Ru-AuNP/GNP/Naf nanocomposite-modified printed sensor

An electrochemiluminescence (ECL) aptasensor for the detection of the milk protein allergen β-lactoglobulin (β-LG) using nanocomposite as luminophore was fabricated. The Ru-AuNPs/GNP/Naf complex was formed by combining the Rubpy₃²⁺-AuNPs complex (Ru-AuNPs), prepared by modifying the negatively charged surface of gold nanoparticles (AuNPs) with positively charged Rubpy₃²⁺ through electrostatic interactions and the graphene nanoplatelets-Nafion (GNP/Naf) at a ratio of 2:1. The nanocomposite was coated on the surface of the screen-printed electrode (SPCE) through the film-forming properties of Nafion. A layer of chitosan (CS) was coated onto this modified electrode, and later amine-terminated β-LG aptamers were covalently attached to the CS/Ru-AuNP/GNP/Naf via glutaraldehyde (GLUT) cross-linking. When β-LG was incubated with the aptasensor, a subsequent decrease in ECL intensity was recorded. Under the optimal conditions, the ECL intensity of the aptasensor changed linearly with the logarithmic concentration of β-LG, in the range 0.1 to 1000 pg/ml, and the detection limit was 0.02 pg/mL (3σ/m). The constructed aptasensor displayed simple and fast determination of β-LG with excellent reproducibility, stability, and high specificity. Additionally, the proposed ECL aptasensor displayed high recoveries (92.5-112%) and low coefficients of variation (1.6-7.8%), when β-LG fortified samples were analyzed. Integrating Ru-AuNPs/GNP/Naf nanocomposite in the ECL aptasensor paves the way towards a cost-effective and sensitive detection of the milk allergen β-LG.

A novel electrochemiluminescence immunosensing strategy fabricated by Co(OH)2 two-dimensional nanosheets and Ru@SiO2-Au NPs for the highly sensitive detection of enrofloxacin

In this work, a novel sensitive electrochemiluminescence immunosensor based on Ru@SiO₂-Au NPs and Co(OH)₂ two-dimensional nanosheets (2D Co(OH)₂) is constructed for the detection of enrofloxacin (ENR). Ruthenium bipyridine silica spheres and modified gold nanoparticles were synthesized as immune probe materials, which were combined with ENR antibodies (Abs) to form the immune probe part. 2D Co(OH)₂ with a large specific surface area and good catalytic effect was firstly used as an immune substrate material, and at the same time, it was conjugated with the coating antigen (Ae) of ENR to form an immune substrate. Based on the principle of competitive immunity, ENR and ENR coated antigen could jointly compete for the specific binding sites on the ENR antibody, so as to achieve efficient detection of ENR. Under optimal conditions, the prepared immunosensor exhibited high sensitivity with a wide linear range from 0.0001 to 1000 ng mL^-1 and a low detection limit (LOD) of 0.063 pg mL^-1. The proposed immunosensor has been successfully applied to the detection of ENR residues in poultry, aquatic products and lake water.

A novel molecularly imprinted electrochemiluminescence sensor based on cobalt nitride nanoarray electrode for the sensitive detection of bisphenol S

A substitute for bisphenol A (BPA), bisphenol S (BPS) has endocrine disruptive and toxic effects and could pose potential risk on human health and the environment. Herein, we fabricated a sensitive molecularly imprinted electrochemiluminescence (MIECL) sensor for the determination of BPS. CoN nanoarray with outstanding electrical conductivity was prepared and it directly served as the sensor platform. Especially, due to the high surface area of the porous CoN nanoarray, the ECL probe of Ru(bpy)3 2+ could be absorbed on the electrode. By means of the cation exchange of Nafion membrane and utilizing tripropylamine (TPrA) as co-reactant, boosted ECL signals were obtained. Meanwhile, by combining with molecularly imprinted polymers (MIPs), the constructed sensor achieved specific recognition of BPS. On the basis of the superior properties of the CoN nanoarray-based electrode, the ECL signal of the proposed sensor was linearly proportional to the BPS concentration from 2.4 × 10-9 to 5.0 × 10-5 mol L-1 (R 2 = 0.9965) with a low limit of detection (LOD) of 8.1 × 10-10 mol L-1 (S/N = 3). To test the accuracy of the proposed method, the HPLC method was adopted to analyze drinking water samples as a comparison. The t-test result proved that discrepancies between HPLC analysis and the method using the fabricated MIECL sensor were acceptable. The developed MIECL sensor with the sensitive, selective, reproducible, and stable analytical performance provides a potential pathway for the detection of BPS and other BPA substitutes in drinking water samples.

Electrochemiluminescence cytosensing platform based on Ru(bpy)32+@silica-Au nanocomposite as luminophore and AuPd nanoparticles as coreaction accelerator for in situ evaluation of intracellular H2O2

An electrochemiluminescence (ECL) cytosensor was fabricated onto a microfluidic paper-based analytical device (μ-PAD) in order to detect hydrogen peroxide (H₂O₂) which was released from tumor cells. The ECL probe Ru(bpy)₃²⁺@silica-Au nanocomposite (Ru@SiO₂-Au) was fabricated and served as ECL reagent. The ECL of Ru@SiO₂-Au nanocomposite was quenched by the ferrocene (Fc). AuPd nanoparticles (AuPd NPs), which were modified on the paper working electrode (PWE), were served as the catalyst of H₂O₂ to produce hydroxyl radicals (•OH) for cleaving Fc-labelled DNA to achieve "signal-on", and AuPd NPs also severed as coreaction accelerator. H₂O₂ was released from cells under the stimulation of phorbol myristate acetate. Fc-labelled DNA strand was cleaved via •OH. Fc molecule departed from the PWE surface, The ECL could be recovered. An ECL cytosensor on a 3D origami device was constructed. The ECL response of the Ru@SiO₂-Au-Fc system was related to the number of cells. The ECL intensity was quantitatively related with the logarithm of MCF-7 cells number and H₂O₂ concentration, the detection limit was 30 cells mL^-1. As a consequence, this work provided a really low-cost and disposable μ-PAD for sensitive detection of intracellular H₂O₂. What's more, this work had potential application value for studying cellular biology and pathophysiology.

Aptasensors as the future of antibiotics test kits-a case study of the aptamer application in the chloramphenicol detection

Antibiotics are a type of antimicrobial drug with the ubiquitous presence in foodstuff that effectively applied to treat the diseases and promote the animal growth worldwide. Chloramphenicol as one of the antibiotics with the broad action spectrum against Gram-positive and Gram-negative bacteria is widely applied for the effective treatment of infectious diseases in humans and animals. Unfortunately, the serious side effects of chloramphenicol, such as aplastic anemia, kidney damage, nausea, and diarrhea restrict its application in foodstuff and biomedical fields. Development of the sufficiently sensitive methods to detect chloramphenicol residues in food and clinical diagnosis seems to be an essential demand. Biosensors have been introduced as the promising tools to overcome the requirement. As one of the newest types of the biosensors, aptamer-based biosensors (aptasensors) are the efficient sensing platforms for the chloramphenicol monitoring. In the present review, we summarize the recent achievements of the accessible aptasensors for qualitative detection and quantitative determination of chloramphenicol as a candidate of the antibiotics. The present chloramphenicol aptasensors can be classified in two main optical and electrochemical categories. Also, the other formats of the aptasensing assays like the high performance liquid chromatography (HPLC) and microchip electrophoresis (MCE) have been reviewed. The enormous interest in utilizing the diverse nanomaterials is also highlighted in the fabrication of the chloramphenicol aptasensors. Finally, some results are presented based on the advantages and disadvantages of the studied aptasensors to achieve a promising perspective for designing the novel antibiotics test kits.

Quenching Electrochemiluminescence Immunosensor Based on Resonance Energy Transfer between Ruthenium (II) Complex Incorporated in the UiO-67 Metal-Organic Framework and Gold Nanoparticles for Insulin Detection

This work describes a sandwich-type electrochemiluminescence (ECL) strategy for insulin detection by using Ru(bpy)₃²⁺ as the luminophore which was encapsulated in the UiO-67 metal-organic framework (UiO-67/Ru(bpy)₃²⁺). Because UiO-67 possesses the characteristics of large specific surface area and porosity, more Ru(bpy)₃²⁺ could be loaded onto its surface and holes, thus greatly improving the ECL efficiency. Furthermore, the ECL resonance energy transfer (ECL-RET) could occur between UiO-67/Ru(bpy)₃²⁺ (ECL donor) and Au@SiO₂ nanoparticles (ECL acceptor), resulting in a conspicuously decreased ECL response. The ECL spectrum of UiO-67/Ru(bpy)₃²⁺ which exhibited strong ECL intensity has suitable spectral overlap with the absorption spectrum of Au@SiO₂, which further proved the occurrence of the ECL-RET action. The ECL intensity decreased with the increase of the concentration of insulin. In addition, the sandwich-type ECL immunosensor was applied to insulin detection, and the ECL decrease efficiency was found to be logarithmically related to the concentration of the insulin antigen in the range of 0.0025 to 50 ng mL^-1 with the limit of detection of 0.001 ng mL^-1. Meanwhile, this work provides an important reference for the application of metal-organic frameworks in the ECL and ECL-RET study and also exhibits potential capability in the detection of other hormones.

Rapid and sensitive spectroelectrochemical and electrochemical detection of glyphosate and AMPA with screen-printed electrodes

N-(Phosphonomethyl)glycine (glyphosate), known by the trade name Roundup®, is a broad spectrum systemic herbicide used to kill several types of grass weed. The hazard potential of Roundup® is unclear, which is a serious issue within the European Union; however, after an intense debate, the EU Commission extended its approval of glyphosate use until the end of 2017. A persistent need exists for rapid, inexpensive, and sensitive detection of glyphosate and (aminomethyl)phosphonic acid (AMPA), the hydrolysis product of glyphosate. This article presents reliable and easily performed (spectro)electrochemical measurements (e.g., electrogenerated chemiluminescence (ECL) and fast amperometry) for identifying glyphosate and AMPA on the basis of [Ru(bpy)3]2+. The limit of detection of both methods is also determined in this study. The main feature of the (spectro)electrochemical methods is screen-printed electrodes (SPE) that are made from either gold or multi-walled carbon nanotubes (MWCNTs), optionally decorated with nano-ZnO. Nano-ZnO can significantly enhance the ECL signal to result in a detection limit lower than 1μmol/L for glyphosate. In addition, these methods are cheaper, faster, and more sensitive than, for example, spectroscopic tests.

A triple-amplification SPR electrochemiluminescence assay for chloramphenicol based on polymer enzyme-linked nanotracers and exonuclease-assisted target recycling

The present study aimed to explore a novel triple-amplification electrochemiluminescence (ECL) assay for detecting of chloramphenicol (CAP). This strategy was based on single-stranded DNA-binding protein (SSB) and horseradish peroxidase (HRP) enzyme-linked polymer (EnVision reagent, EV) labeled on Au nanoparticles (EV-Au-SSB) as nanotracer and exonuclease-assisted target recycling. The composite probes were prepared via immunoreactions between the CdS nanocrystal (CdS NC)-functionalized partial complementary DNA and aptamer (CdSNCs/Apt-ssDNA1) as capture probes, and EV-Au-SSB as nanotracer. When the composite probe solution co-existed with CAP and Exo I, the aptamer on the capture probes preferentially combined with CAP, and then CAP-Apt and nanotracer complex were released into the solution. Subsequently, Exo I in the solution could further digest the CAP-Apt from the 3'-end of the aptamer and release CAP, which could participate in further reaction with the probes. It was worth mentioning that EV contained a large number of HRPs on its dendritic chain. In the EV-Au-SSB, Au could enhance ECL intensity of CdS NCs by surface plasmon resonance. What's more, HRPs on EV could catalyze the reaction of H2O2, which could obviously enhance ECL intensity of CdS NCs. This study demonstrated excellent performance of the triple-amplification ECL assay, which makes this aptasensor system suitable and promising for the practical application of CAP residues in fish samples. Moreover, the assay might provide a promising avenue to develop efficient aptasensors to determine small-molecule harmful substances in environmental monitoring and food safety.

A solid-state electrochemiluminescent sensor based on C60/graphite-like carbon nitride nanosheet hybrids for detecting melamine

Schematic illustration of preparing C₆₀/g-C₃N₄ NS and the fabricating procedures of the proposed ECL sensor.

Ratiometric biosensor array for multiplexed detection of microRNAs based on electrochemiluminescence coupled with cyclic voltammetry

A novel multiplexed ratiometric biosensor array was fabricated on a homemade screen-printed carbon electrode (SPCE) for near-simultaneous detection of microRNA (miRNA)-21 and miRNA-141 based on electrochemiluminescence (ECL) coupled with cyclic voltammetry (CV) method. In the detection system, the ECL signal tags (Ru-SiO2@PLL-Au) were fabricated using poly-l-lysine (PLL) as bridging agent and co-reactant to connect Ru-SiO2 (Ru(bpy)3(2+)-doped silica) and gold nanoparticles (Au NPs), which were respectively modified on two spatial resolved working electrodes (WE1 and WE2) of SPCE. Then the ferrocene (Fc)-labeled hairpin DNA (Fc-HDNA1 and Fc-HDNA2) as CV signal tags and ECL quenching material were immobilized on Ru-SiO2@PLL-Au. Upon miRNA-21 and miRNA-141 adding, the target miRNAs could hybridize with corresponding Fc-HDNA, which could lead to Fc away from Ru-SiO2@PLL-Au. Such conformational changes could recover the ECL of Ru-SiO2@PLL-Au and decreased the CV current of Fc, respectively. This "signal-on" of ECL and "signal-off" of CV were employed for dual-signal ratiometric readout. With the help of a multiplexed switch, two dual-signals from WE1 and WE2 were used for multiplexed detection of miRNA-21 and miRNA-141 down to 6.3 and 8.6fM, respectively. This approach was used in real sample analysis and has significant potential for miRNA biomarkers detection in a clinical laboratory setting.