A sensitive electrochemiluminescence folic acid sensor based on a 3D graphene/CdSeTe/Ru(bpy)32+-doped silica nanocomposite modified electrode

Self-luminescent dual-ligand metal-organic framework based electrochemiluminescence probes for organophosphorus pesticides determination

In this study, a signal amplification strategy was developed, which tris (2, 2'-bipyridyl) ruthenium (II) (Ru(bpy)32+) was incorporated as a guest molecule into the preparation system of lanthanide-based metal-organic framework (MOF). This strategy relied on strong electrostatic interactions and coordination competition to influence the growth process of the MOF, resulting in the firm immobilization of Ru(bpy)32+ within the MOF structure. The spatial confinement effect of the MOF effectively improved the efficiency of electron transfer in the electrochemiluminescence (ECL) reaction. The constructed ECL aptasensor using this MOF exhibited excellent performance, with limits of detection (LODs) for four organophosphorus pesticides (OPs), phorate, profenofos, isocarbophos and omethoate, as low as 0.0482 ng/mL, 0.0093 ng/mL, 0.0085 ng/mL, and 0.0893 ng/mL, respectively. This work has paved the way for a clever strategy of immobilizing Ru(bpy)32+ molecules and amplifying signals, expanding the application of dual-ligand MOF, which provides valuable insights for future biosensor design.

Engineered Electrochemiluminescence Biosensors for Monitoring Heavy Metal Ions: Current Status and Prospects

Metal ion contamination has serious impacts on environmental and biological health, so it is crucial to effectively monitor the levels of these metal ions. With the continuous progression of optoelectronic nanotechnology and biometrics, the emerging electrochemiluminescence (ECL) biosensing technology has not only proven its simplicity, but also showcased its utility and remarkable sensitivity in engineered monitoring of residual heavy metal contaminants. This comprehensive review begins by introducing the composition, advantages, and detection principles of ECL biosensors, and delving into the engineered aspects. Furthermore, it explores two signal amplification methods: biometric element-based strategies (e.g., HCR, RCA, EDC, and CRISPR/Cas) and nanomaterial (NM)-based amplification, including quantum dots, metal nanoclusters, carbon-based nanomaterials, and porous nanomaterials. Ultimately, this review envisions future research trends and engineered technological enhancements of ECL biosensors to meet the surging demand for metal ion monitoring.

Signal-amplified electrochemiluminescence aptasensor for mucin 1 determination using CdS QDs/g-C3N4 and Au NPs@TEOA

A novel electrochemiluminescence (ECL) aptasensor, using graphite carbonitride (g-C₃N₄) capped CdS quantum dots (CdS QDs@g-C₃N₄) and Au nanoparticles decorated triethanolamine (AuNPs@TEOA) as dual coreactants, was proposed for the determination of mucin 1 (MUC1). Higher ECL efficiency was acquired due to the double enhancement contribution of CdS QDs and TEOA to Ru (bpy)₃²⁺ ECL. Additionally, AuNPs@TEOA also acted as nanocarrier for MUC1 aptamer immobilization. After the aptasensor was incubated in target MUC1, the decreased ECL emission was obtained because of the poor conductivity of MUC1. The ECL aptasensor displayed a good linear correlation for MUC1 in the range 0.1 pg mL^-1 -1000 ng mL^-1, and the detection limit was 33 fg mL^-1. MUC1 spiked into human serum samples was quantified to assess the practicability of the ECL aptasensor.

The role of doping strategy in nanoparticle-based electrochemiluminescence biosensing

Doping plays a crucial role in electrochemiluminescence (ECL) due to the followings: (1) Modulation of electronic structure, alteration of the surface state of nanoparticles (NPs), providing effective protection from the surrounding environment, thereby leading to ECL emitters with exceptional properties including tunable spectra, high luminescence efficiency, low excitation potential, and good stability. (2) Employment of doped NPs as promising coreactant alternatives due to the presence of functional groups such as amines induced by NP doping. (3) Serving as novel co-reaction accelerators (CRAs) for ECL through doping induced high catalytic properties. (4) Behaving as excellent carriers to load ECL emitters, recognition elements, and catalysts due to doping-induced larger surface area, higher conductivity and better biocompatibility of NPs. As a consequence, doped NPs have aroused broad interest and found wide applications in various ECL sensing platforms. In this review, the current promising improvements, concepts, and excellent applications of doped NPs for ECL biosensing are addressed. We aim to bring to light the physicochemical characteristics of various doped NPs that endow them with appealing ECL performance, leading to diverse applications in biosensing.

Achievements of Graphene and Its Derivatives Materials on Electrochemical Drug Assays and Drug-DNA Interactions

Graphene, emerging as a true two-dimensional (2D) material, has attracted increasing attention due to its unique physical and electrochemical properties such as high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production. The entire scientific community recognizes the significance and potential impact of graphene. Electrochemical detection strategies have advantages such as being simple, fast, and low-cost. The use of graphene as an excellent interface for electrode modification provides a promising way to construct more sensitive and stable electrochemical (bio)sensors. The review presents sensors based on graphene and its derivatives for electrochemical drug assays from pharmaceutical dosage forms and biological samples. Future perspectives in this rapidly developing field are also discussed. In addition, the interaction of several important anticancer drug molecules with deoxyribonucleic acid (DNA) that was immobilized onto graphene-modified electrodes has been detailed in terms of dosage regulation and utility purposes.

A novel signal amplified electrochemiluminescence biosensor based on MIL-53(Al)@CdS QDs and SiO2@AuNPs for trichlorfon detection

An ultrasensitive electrochemiluminescence (ECL) biosensor was developed based on MIL-53(Al)@CdS QDs and SiO₂@AuNPs for trichlorfon detection. Metal-organic frameworks (MOFs) were used as a loading platform that provided a large surface area to load targets and modified materials onto the electrode. At the same time, SiO₂@AuNPs loaded plenty of AuNPs which effectively increased the ECL resonance energy transfer between the CdS QDs, so that the ECL signal was strongly quenched and resulted in an amplified response. In the range of 10^-11-10^-4 M, the ECL response showed a linear relationship with the concentration (logarithm) of trichlorfon, and the detection limit was 5.1 × 10^-12 M (S/N = 3). When the biosensor was applied to detect trichlorfon in lettuce, broccoli, cucumber, and chives, the recoveries obtained from the spiked samples were 97%-105%, 102%-104%, 100%-104%, and 98%-104%, respectively. Thus, this novel ECL biosensor has potential applications for the analysis of trichlorfon in food samples.

A highly-enhanced electrochemiluminescence luminophore generated by a metal-organic framework-linked perylene derivative and its application for ractopamine assay

In this study, a sensitive and effective monitoring method for ractopamine (RAC) was developed based on a sensitive electrochemiluminescence (ECL) aptasensor. Here, we employed a perylene derivative (PTC-PEI) with a Cu-based metal-organic framework (HKUST-1), which could accelerate the electron-transfer (ET) rate and strengthen interactions by the amido bond, resulting in enhanced ECL sensitivity and stability. Astonishingly, compared with the response of PTC-PEI and complex, the ECL signal of the MOF-based ECL material was noticeably raised by 6 times higher than that of PTC-PEI. HKUST-1 exhibited an excellent catalytic effect towards the electrochemical reduction process of S₂O₈^2-, thus allowing more sulfate radical anions (SO₄˙^-) to be generated. The strong ECL intensity of HKUST-1/PTC-PEI not only stemmed from the fixation of PTC-PEI that utilized its excellent film-forming abilities but also originated from the high porosity of HKUST-1 that carried more luminophores able to be excited. Satisfyingly, in the presence of the target molecule RAC, we observed an obvious quenching effect of signal, which could be attributed to aptamer recognition resulting in RAC being specifically captured on the electrode. Under optimal conditions, the developed sensor for the RAC assay displayed a desired linear range of 1.0 × 10^-12-1.0 × 10^-6 M and a low detection limit of 6.17 × 10^-13 M (S/N = 3). This ECL sensor showed high sensitivity, good stability and excellent selectivity. More importantly, the proposed aptasensor exhibited excellent determination towards RAC detection and potential practical utility for real samples.

Fluorescent AgInS/ZnS quantum dots microplate and lateral flow immunoassays for folic acid determination in juice samples

A noninstrumental rapid test for folic acid (FA) detection with visual results evaluation utilizing bright water-stable AgInS/ZnS (AIS/ZnS) quantum dots (QDs) is reported . AIS/ZnS QDs are hydrophilic photostable nanocrystals with size < 7 nm and emission in the visible range. They were synthesized directly in the water phase by a simple method compared to the synthesis of other QDs and conjugated with monoclonal antibodies specific for FA via ligand carboxyl groups. The conjugate was used for the development of instrumental qualitative and rapid quantitative FA detection methods. The competitive fluorescent microplate immunosorbent assay provided a limit of detection of 0.1 ng/mL FA and half maximal inhibitory concentration (IC₅₀) of 24 ng/mL FA. The analytical signal was measured at ʎ_ex = 410 nm and ʎ_em=590 nm. The proposed method showed no cross-reaction with other group B vitamins. For FA screening in juice samples, the lateral flow immunoassay was developed with a visual cutoff level of 3 μg/mL. In our perception, the developed methods are convenient for proving the perception of the AIS/ZnS QDs application as a luminescent label for immunoassay and are effective for FA detection. Graphical abstract.

Electrochemiluminescence aptasensor for multiple determination of Hg2+ and Pb2+ ions by using the MIL-53(Al)@CdTe-PEI modified electrode

An aptasensor based on MIL-53(Al)@CdTe was designed for multiple determination of Hg²⁺ and Pb²⁺ by electrochemiluminescence (ECL). Upon the recognition of Hg²⁺, aptamer 2-AuNPs form hairpin structures and are removed from the electrode. While in the presence of Pb²⁺, aptamer 1-PtNPs capture the target ions and form G-quadruplexes, and then bring PtNPs close enough to CdTe QDs to produce ECL resonance energy transfer. Upon aptamer interaction with Hg²⁺ and Pb²⁺, decreased ECL intensity was observed due to enhanced resonance energy transfer (ERET) and attenuated surface plasmon resonance (SPR). The ECL intensity difference (ΔECL) could therefore be used to detect heavy-metal ions with detection limits of 4.1 × 10^-12 M (path 1, Hg²⁺), 3.7 × 10^-11 M (path 2, Pb²⁺), and 2.4 × 10^-11 M (path 3, Pb²⁺). The aptasensor could also be used for detecting Hg²⁺ and Pb²⁺ in fish and shrimp samples with good recoveries.

A fluorescent sensor for folic acid based on crown ether-bridged bis-tetraphenylethylene

Aggregation-induced emission (AIE) provides a new strategy for preparing fluorescent sensors in aggregated state. In this paper, a series of crown ether-bridged bis-tetraphenylethylene compounds were synthesized in 78-84% yield by a simple procedure. The molecules exhibited excellent AIE properties in THF/H2O solutions and solid films. The investigation on sensing abilities for various biomolecules and metal ions suggested that Bis-TPE-1 possessed obvious response to folic acid, with fluorescence enhancement and blue shift of maximum emission wavelength from 380 nm to 365 nm. The detection limit for folic acid was 6.36 × 10-7 M, and the sensor's selectivity for folic acid was little interfered by the other species. The sensor mechanism was studied by FT-IR, 1H NMR, MS spectra and fluorescence Jobs' plot. The selective sensor for folic acid was applied in test paper and the analyses of real samples of mung bean and spinach. The superior bioimaging performance of Bis-TPE-1 for sensing folic acid was confirmed by the live cell imaging experiments, which indicated its good practical application potential for detecting folic acid.

Ru(bpy)32+-Silica@Poly-L-lysine-Au as labels for electrochemiluminescence lysozyme aptasensor based on 3D graphene

In this work, the feasibility of a novel sensitive electrochemiluminescence aptasensor for the detection of lysozyme using Ru(bpy)₃²⁺-Silica@Poly-L-lysine-Au (RuSiNPs@PLL-Au) nanocomposites labeling as an indicator was demonstrated. The substrate electrode of the aptasensor was prepared by depositing gold nanoparticles (AuNPs) on 3D graphene-modified electrode. The lysozyme binding aptamer (LBA) was attached to the 3D graphene/AuNPs electrode through gold-thiol affinity, hybridized with a complementary single-strand DNA (CDNA) of the lysozyme aptamer labeled by RuSiNPs@PLL-Au as an electrochemiluminescence intensity amplifier. Thanks to the synergistic amplification of the 3D graphene, the AuNPs and RuSiNPs@PLL-Au NPs linked to Ru(bpy)₃²⁺-ECL further enhanced the ECL intensity of the aptasensor. In presence of lysozyme, the CDNA segment of the self-assembled duplex was displaced by the lysozyme, resulting in decreased electrochemiluminescence signal. Under the optimized conditions, the decrease in electrochemiluminescence intensity varied proportionally with the logarithmic concentration of the lysozyme from 2.25 × 10^-12 to 5.0 × 10^-8 mol L^-1, and the detection limit was estimated to 7.5 × 10^-13 mol L^-1. The aptasensor was further tested in real samples and found reliable for the detection of lysozyme, thus holding great potential application in food safety researches and bioassay analysis.

The recognition and electrochemiluminescence response of benzo[6]urils to polycyclic aromatic hydrocarbons

The electrochemiluminescence of benzo[6]urils was discovered and applied for molecular recognition based on the host–guest interactions with polycyclic aromatic hydrocarbons.

11-Mercaptoundecanoic acid capped gold nanoclusters as a fluorescent probe for specific detection of folic acid via a ratiometric fluorescence strategy

A novel ratiometric fluorescence strategy is developed for specific detection of folic acid (FA) by using 11-mercaptoundecanoic acid protected gold nanoclusters (AuNCs@MUA). In this design, the fluorescence color of the probe can be switched among red, pink, violet and blue by varying the concentration of FA. AuNCs@MUA possesses strong fluorescence peaking at 612 nm (R-signal) and FA exhibits blue emissive auto-fluorescence at 446 nm (B-signal), showing a large emission shift of ∼170 nm. When AuNCs@MUA approaches FA through electrostatic binding, the R-signal decreases while the B-signal increases with titration of FA. Based on the above phenomenon, a radiometric analysis platform is constructed for FA target detection, with a wide linear response range from 0 to 20 μM, and an excellent detection limit of 26 nM. This new ratiometric strategy exhibits low background, and wide signal changes in a low concentration range, which presents obvious advantages over most previous FA detections based on single-responsive fluorescence methods. Furthermore, the proposed method is successfully applied to determine FA in human serum samples.

A novel ratiometric fluorescence strategy is developed for specific detection of folic acid (FA) by using 11-mercaptoundecanoic acid protected gold nanoclusters (AuNCs@MUA).