Co-Quenching Effect between Lanthanum Metal-Organic Frameworks Luminophore and Crystal Violet for Enhanced Electrochemiluminescence Gene Detection

An electrochemiluminescence sensor based on Ag NPs amplifying PDDA-modified TbPO4:Ce NWs signal for sensitive detection of lincomycin

The residue of lincomycin in water will not only aggravate the drug resistance of bacteria but also cause damage to the human body through biological accumulation. In this work, an electrochemiluminescence (ECL) aptasensor for the detection of lincomycin was constructed based on polydimethyldiallylammonium chloride (PDDA) functionalized Ce-doped TbPO4 nanowires (PDDA-TbPO4:Ce NWs) and silver nanoparticles (Ag NPs). TbPO4:Ce NWs were used as the luminophore, and PDDA was used to functionalize the luminophore to make the surface of the luminophore positively charged. The negatively charged silver nanoparticles were combined with PDDA-TbPO4:Ce NWs by electrostatic interaction. Ag NPs accelerated the electron transfer rate and promoted the ECL efficiency, which finally increased the ECL intensity of TbPO4:Ce NWs by about 4 times. Under the optimal conditions, the detection limit of the ECL sensor was as low as 4.37 × 10-16 M, and the linear range was 1 × 10 - 15 M to 1 × 10 - 5 M, with good selectivity, stability, and repeatability. The sensor can be applied to the detection of lincomycin in water, and the recovery rate is 97.7-103.4 %, which has broad application prospects.

Dual-potential ratiometric electrochemiluminescence based on single emitter and single coreactant for the sensitive detection of carcinoembryonic antigen

Dual-potential ratiometric electrochemiluminescence (ECL) is in favor of resistance to environmental interference. However, two kinds of emitters or coreactants, and a wide scan potential range (>2 V) are mandatory. This work developed a new dual-potential ratiometric ECL sensor for detection of carcinoembryonic antigen (CEA) using single emitter (luminol) and single coreactant (H2O2) with a mild potential range from -0.1 to 0.6 V. Luminol could produce a strong cathodic ECL (Ec) induced by hydroxyl radicals (HO‧) from the reduction of H2O2, and a relatively weak anodic ECL (Ea). After the ferrocene modified CEA aptamer (Apt-Fc) was attached, Fc could promote Ea by catalyzing the oxidation of H2O2, and reduce Ec by consuming HO‧. With the cycling amplification of the exonuclease I, CEA could substantially reduce the amount of Apt-Fc, resulting in the decrease of Ea and the rise of Ec. So, the ratio of Ec to Ea (Ec/Ea) was used as the detection signal, realizing the sensitive determination of CEA from 0.1 pg mL-1 to 10 ng mL-1 with a LOD of 41.85 fg mL-1 (S/N = 3). The developed sensor demonstrated excellent specificity, stability and reproducibility, with satisfactory results in practical detection.

FeNi-MIL-88B-based electrochemiluminescence immunosensor for ultra-sensitive detection of CD44 protein via dual-quenching strategy

BACKGROUND

Cluster of Differentiation 44 (CD44) is considered an important biomarker for various cancers, and achieving highly sensitive detection of CD44 is crucial, which plays a significant role in tumor invasion and metastasis, providing essential information for clinical tumor diagnosis. Commonly used methods for analysis include fluorescence spectroscopy (FL), photoelectrochemical analysis (PEC), electrochemical analysis (EC), and commercial ELISA kits. Although these methods offer high sensitivity, they can be relatively complex to perform experimentally. Electrochemiluminescence (ECL) has gained widespread research attention due to its high sensitivity, ease of operation, effective spatiotemporal control, and close to zero background signal.

RESULTS

In this work, a sandwich-type ECL immunosensor for detecting CD44 was constructed using luminol as a luminophore. In this sensing platform, bimetallic MOFs (Pd@FeNi-MIL-88B) loaded with palladium nanoparticles (Pd NPs) were used as a novel enzyme mimic, exhibiting excellent catalytic performance towards the electroreduction of H2O2. The hybrids provided a strong support platform for luminol and antibodies, significantly enhancing the initial ECL signal of luminol. Subsequently, core-shell Au@MnO2 nanocomposites were synthesised by gold nanoparticles (Au NPs) encapsulated in manganese dioxide (MnO2) thin layers, as labels. In the luminol/H2O2 system, Au@MnO2 exhibited strong light absorption in the broad UV-vis spectrum, similar to the black body effect, and the scavenging effect of Mn2+ on O2•-, which achieved the dual-quenching of ECL signal. Under the optimal experimental conditions, the immunosensor demonstrated a detection range of 0.1 pg mL-1 - 100 ng mL-1, with a detection limit of 0.069 pg mL-1.

SIGNIFICANCE

Based on Pd@FeNi-MIL-88B nanoenzymes and Au@MnO2 nanocomposites, a dual-quenching sandwich-type ECL immunosensor for the detection of CD44 was constructed. The proposed immunosensor exhibited excellent reproducibility, stability, selectivity, and sensitivity, and provided a valuable analytical strategy and technical platform for the accurate detection of disease biomarkers, and opened up potential application prospects for early clinical treatment.

A novel PEC and ECL bifunctional aptasensor based on V2CTx MXene-derived MOF embedded with silver nanoparticles for selectively aptasensing miRNA-126

A novel photoelectrochemical (PEC) and electrochemiluminescence (ECL) bifunctional aptasensor has been established for the detection of miRNA-126 using V2CTx MXene-derived porphyrin-based metal-organic framework embedded with Ag nanoparticles (Ag NPs) (denoted as AgNPs@V-PMOF) as a robust bioplatform. Due to the presence of V nodes in V2CTx MXene nanosheets, V-based MOF was prepared using tetrakis(4-carboxyphenyl)porphyrin as ligand, followed by the incorporation of Ag+ ions to form the AgNPs@V-PMOF Schottky heterojunction. Benefiting from the fast electron transfer of the V2CTx substrate and well-matched band-edge energy level of the photosensitive Ag NPs and V-PMOF, the constructed AgNPs@V-PMOF Schottky heterojunction exhibited the promoted transfer of the photogenerated carriers, showing superior PEC and ECL performances. Moreover, a large number of the complementary DNA strand of miRNA-126 can be immobilized over AgNPs@V-PMOF in view of the combined interaction of π-π stacking, van der Waals force, and Ag-N coordination between AgNPs@V-PMOF. Consequently, the developed AgNPs@V-PMOF-based aptasensor illustrated extremely low detection limits of 0.78 and 0.53 fM within a wide range from 1.0 fM to 1.0 nM of miRNA-126 detected by PEC and ECL techniques, respectively, superior to most reported miRNA aptasensors. Also, the provided bifunctional aptasensor demonstrated high selectivity, good stability, fine reproducibility, and acceptable regenerability, as well as promising potential for the analysis of miRNA-126 from living cancer cells. This work puts forward the development of aptasensors for the early and accurate diagnosis of cancer markers and extends the application of MOF in the biosensing field.

Nanoporous Crystalline Materials for the Recognition and Applications of Nucleic Acids

Nucleic acid plays a crucial role in countless biological processes. Hence, there is great interest in its detection and analysis in various fields from chemistry, biology, to medicine. Nanoporous crystalline materials exhibit enormous potential as an effective platform for nucleic acid recognition and application. These materials have highly ordered and uniform pore structures, as well as adjustable surface chemistry and pore size, making them good carriers for nucleic acid extraction, detection, and delivery. In this review, the latest developments in nanoporous crystalline materials, including metal organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular organic frameworks (SOFs) for nucleic acid recognition and applications are discussed. Different strategies for functionalizing these materials are explored to specifically identify nucleic acid targets. Their applications in selective separation and detection of nucleic acids are highlighted. They can also be used as DNA/RNA sensors, gene delivery agents, host DNAzymes, and in DNA-based computing. Other applications include catalysis, data storage, and biomimetics. The development of novel nanoporous crystalline materials with enhanced biocompatibility has opened up new avenues in the fields of nucleic acid analysis and therapy, paving the way for the development of sensitive, selective, and cost-effective diagnostic and therapeutic tools with widespread applications.

Newly Developed Electrochemiluminescence Based on Bipolar Electrochemistry for Multiplex Biosensing Applications: A Consolidated Review

Recently, there has been an upsurge in the extent to which electrochemiluminescence (ECL) working in synergy with bipolar electrochemistry (BPE) is being applied in simple biosensing devices, especially in a clinical setup. The key objective of this particular write-up is to present a consolidated review of ECL-BPE, providing a three-dimensional perspective incorporating its strengths, weaknesses, limitations, and potential applications as a biosensing technique. The review encapsulates critical insights into the latest and novel developments in the field of ECL-BPE, including innovative electrode designs and newly developed, novel luminophores and co-reactants employed in ECL-BPE systems, along with challenges, such as optimization of the interelectrode distance, electrode miniaturization and electrode surface modification for enhancing sensitivity and selectivity. Moreover, this consolidated review will provide an overview of the latest, novel applications and advances made in this field with a bias toward multiplex biosensing based on the past five years of research. The studies reviewed herein, indicate that the technology is rapidly advancing at an outstanding purse and has an immense potential to revolutionize the general field of biosensing. This perspective aims to stimulate innovative ideas and inspire researchers alike to incorporate some elements of ECL-BPE into their studies, thereby steering this field into previously unexplored domains that may lead to unexpected, interesting discoveries. For instance, the application of ECL-BPE in other challenging and complex sample matrices such as hair for bioanalytical purposes is currently an unexplored area. Of great significance, a substantial fraction of the content in this review article is based on content from research articles published between the years 2018 and 2023.

Electrochemiluminescence resonance energy transfer between Ru(bpy)32+@Cu3(HHTP)2 and GO-Au composites for C-reactive protein detection

Designing innovative electrochemiluminescence (ECL) immunosensors is critical for the detection of biomarkers with a low concentration and the precise evaluation of clinical diseases. Herein, a Cu₃(hexahydroxytriphenylene)₂ (Cu₃(HHTP)₂) nanoflake-based sandwich-type ECL immunosensor was constructed for C-Reactive Protein (CRP) detection. The Cu₃(HHTP)₂ nanoflake, an electronically conductive metal-organic framework (MOF), has a periodically arranged porous structure with a cavity size of 2 nm, which not only accommodates a large amount of Ru(bpy)₃²⁺ but also confines the spatial diffusion of active species. Therefore, the Ru(bpy)₃²⁺-loaded Cu₃(HHTP)₂ nanocomplex (Ru@CuMOF) as an ECL emitter exhibits an enhanced ECL efficiency. The ECL resonance energy transfer (ECL-RET) was accomplished by combining Ru@CuMOF used as a donor with gold nanoparticles-functionalized graphene oxide nanosheets (GO-Au) utilized as an acceptor. This should be ascribed to the fact that the ECL emission spectrum of Ru@CuMOF shows the strongest signal intensity at 615 nm, overlapping with the absorption spectrum of GO-Au at 580-680 nm. Targeted detection of CRP in human serum samples was achieved by the sandwich-type immunosensor based on the ECL-RET mechanism with a 0.26 pg mL^-1 detection limit. The electro-activated hybrids of Cu₃(HHTP)₂ and ECL emitters provide a new sensing strategy for the high-sensitivity detection of disease markers.

Electrochemical sensor based on Fe3O4/α-Fe2O3@Au magnetic nanocomposites for sensitive determination of the TP53 gene

Considering the high cost and tedious process of gene sequencing, there is an urgent need to develop portable and efficient sensors for the TP53 gene. Here, we developed a novel electrochemical sensor that detected the TP53 gene using magnetic peptide nucleic acid (PNA)-modified Fe₃O₄/α-Fe₂O₃@Au nanocomposites. Cyclic voltammetry and electrochemical impedance spectroscopy confirmed the successful stepwise construction of the sensor, especially the high-affinity binding of PNA to DNA strands, which induced different electron transfer rates and resulted in current changes. Variations in the differential pulse voltammetry current observed during hybridization at different surface PNA probe densities, hybridization times, and hybridization temperatures were explored. The biosensing strategy obtained a limit of detection of 0.26 pM, a limit of quantification of 0.85 pM, and a wide linear range (1 pM-1 μM), confirming that the Fe₃O₄/α-Fe₂O₃@Au nanocomposites and the strategy based on magnetic separation and magnetically induced self-assembly improved the binding efficiency of nucleic acid molecules. The biosensor was a label-free and enzyme-free device with excellent reproducibility and stability that could identify single-base mismatched DNA without additional DNA amplification procedures, and the serum spiked experiments revealed the feasibility of the detection approach.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Perspectives of metal-organic framework nanosystem to overcome tumor drug resistance

Cancer is one of the most harmful diseases in the world, which causes huge numbers of deaths every year. Many drugs have been developed to treat tumors. However, drug resistance usually develops after a period of time, which greatly weakens the therapeutic effect. Tumor drug resistance is characterized by blocking the action of anticancer drugs, resisting apoptosis and DNA repair, and evading immune recognition. To tackle tumor drug resistance, many engineered drug delivery systems (DDS) have been developed. Metal-organic frameworks (MOFs) are one kind of emerging and promising nanocarriers for DDS with high surface area and abundant active sites that make the functionalization simpler and more efficient. These features enable MOFs to achieve advantages easily towards other materials. In this review, we highlight the main mechanisms of tumor drug resistance and the characteristics of MOFs. The applications and opportunities of MOF-based DDS to overcome tumor drug resistance are also discussed, shedding light on the future development of MOFs to address tumor drug resistance.

Cluster-Dominated Electrochemiluminescence of Tertiary Amines in Polyethyleneimine Nanoparticles: Mechanism Insights and Sensing Application

Designing and screening highly efficient and cost-effective luminophores have always been a challenge to develop sensitive electrochemiluminescence (ECL) biosensors. Herein, polyethyleneimine nanoparticles (PEI NPs), a kind of nonconjugated polymer (NCP) NPs with tertiary amine clusters, were developed as an ECL luminophore. Specifically, PEI NPs were synthesized by a one-step hydrothermal method using PEI and formaldehyde. The properties of PEI NPs were investigated in detail using photochemical and electrochemical techniques. The results showed cluster-dominated luminescence of tertiary amines in PEI NPs via "through-space conjugation". This non-negligible ECL performance (at 631 nm) was also verified by the initiated reduction-oxidation process. With persulfate as a coreactant, PEI NPs acted as both the luminophore and coreaction accelerator to enhance the ECL intensity remarkably, which was eightfold higher than that of isolated PEI. Moreover, choosing dopamine as the model target, a highly sensitive "signal off" ternary ECL sensor was constructed utilizing PEI NPs as the luminophore. Dopamine could be oxidized to benzoquinone at the sensing interface, quenching the signal via ECL energy transfer. Free from any signal amplification, the proposed sensor achieved a low detection limit (4.3 nM) for target monitoring with good selectivity and stability. This strategy not only provides a unique perspective for designing novel efficient and facile ECL luminophores of tertiary amines but also broadens the biological application of NCP NPs.

Electrochemiluminescence Systems for the Detection of Biomarkers: Strategical and Technological Advances

Electrochemiluminescence (ECL)-based sensing systems rely on light emissions from luminophores, which are generated by high-energy electron transfer reactions between electrogenerated species on an electrode. ECL systems have been widely used in the detection and monitoring of diverse, disease-related biomarkers due to their high selectivity and fast response times, as well as their spatial and temporal control of luminance, high controllability, and a wide detection range. This review focuses on the recent strategic and technological advances in ECL-based biomarker detection systems. We introduce several sensing systems for medical applications that are classified according to the reactions that drive ECL signal emissions. We also provide recent examples of sensing strategies and technologies based on factors that enhance sensitivity and multiplexing abilities as well as simplify sensing procedures. This review also discusses the potential strategies and technologies for the development of ECL systems with an enhanced detection ability.

Dumbbell Plate-Shaped AIEgen-Based Luminescent MOF with High Quantum Yield as Self-Enhanced ECL Tags: Mechanism Insights and Biosensing Application

It is widely known that high-performance electrochemiluminescence (ECL) emitters play a crucial part in improving the detection sensitivity of the ECL strategy. Through the combination of aggregation-induced emission luminogens (AIEgens), 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene (H₄ TCBPE) with Zr(IV) cations, a dumbbell plate-shaped metal-organic framework (MOF) with high luminous efficiency is synthesized as ECL tags. The resultant MOF exhibits stronger ECL activity than those of H₄ TCBPE monomers and aggregates. Herein, this phenomenon is defined as the coordination-triggered electrochemiluminescence (CT-ECL) enhancement effect. Furthermore, the nearly matched ECL and photoluminescence (PL) spectra imply the bandgap emission mechanism. Remarkably, polyethyleneimine (PEI) as the coreactant is covalently connected with MOF to form the uniquely self-enhanced ECL complex of Zr-TCBPE-PEI, where the robust ECL signal is captured owing to the intramolecular-like coreaction acceleration. Based on the resonance energy transfer (RET) behavior, the AuPd@SiO₂ composite is designed as the high-efficiency quencher. In this manner, an innovative and ultrasensitive ECL sensor is constructed for neuron-specific enolase (NSE) detection through sandwich-type immunoreaction, with the detection limit down to 52 fg ml^-1 . The present study has gone some way toward designing MOF-based self-luminescent ECL materials, thus paving a new avenue to expand the late-model ECL emitters for immunoassay.