Ru(bpy)32+ encapsulated cyclodextrin based metal organic framework with improved biocompatibility for sensitive electrochemiluminescence detection of CYFRA21-1 in cell

Electrochemiluminescence and fluorescence dual-mode monitoring of aflatoxin B1 production based on single Ru-MOF particles and FITC luminophores

Herein, an electrochemiluminescence (ECL) and fluorescence (FL) dual-mode imaging biosensing platform was developed for onsite and dynamic monitoring of aflatoxin B1 (AFB1) production in the corn molding process. Zinc metal organic framework structures encapsulated with Ru(bpy)32+ (Ru-MOF) were employed as ECL signal probes for single particle imaging with stable luminescent intensity and high emission efficiency. Fluorescein Isothiocyanate (FITC) luminophores, served as fluorescent probes, were conjugated with AFB1 aptamer modified on the electrode surface, which enabled the observation of green luminescent spots in FL mode. When exposed to target AFB1, FITC luminophores detached from the surface of electrode, leading to a notable decrease in the number of green luminescent spots. Single Ru-MOF particles were then immobilized onto the surface of electrode through DNA coupling and discernible luminescent spots could be watched in ECL mode. Under optimal circumstances, a dual-mode imaging platform was constructed for AFB1 determination with a linear relationship of 1.0 fg/mL to 1.0 pg/mL in both ECL and FL mode. The detection limit (LOD) was 0.89 fg/mL in FL mode and 0.84 fg/mL in ECL mode, which demonstrated superior sensitivity. The imaging biosensor was established for dynamic tracking of AFB1 production in corn molding process. The results showed that aflatoxin production occurred more rapidly at damaged areas of the corn compared to areas with intact surfaces. The intact corn got moldy on the third day and its surface AFB1 concentration was calculated as 14.16 fg/mL. Combining the ECL and FL imaging technology with dual-mode biosensing, this work achieves high sensitivity, accuracy and capability of dynamic monitoring for AFB1 sensing which provides innovative ideas for the rational design of aflatoxin sensors, and holds substantial promise in food safety.

Research Progress of Electrochemical Biosensors for Diseases Detection in China: A Review

Disease diagnosis is not only related to individual health but is also a crucial part of public health prevention. Electrochemical biosensors combine the high sensitivity of electrochemical methods with the inherent high selectivity of biological components, offering advantages such as excellent sensitivity, fast response time, and low cost. The generated electrical signals have a linear relationship with the target analyte, allowing for identification and concentration detection. This has become a very attractive technology. This review offers a summary of recent advancements in electrochemical biosensor research for disease diagnosis in China. It systematically categorizes and summarizes biosensors developed in China for detecting cancer, infectious diseases, inflammation, and neurodegenerative disorders. Additionally, the review delves into the fundamental working principles, classifications, materials, preparation techniques, and other critical aspects of electrochemical biosensors. Finally, it addresses the key challenges impeding the advancement of electrochemical biosensors in China and examines promising future directions for their development.

Electrochemiluminescence Immunoassay of cTnI with Ruthenium-Based Metal Covalent Organic Framework and Dual DNAzymes Cascade Amplification Strategy

Currently, metal-organic frameworks (MOFs) with tunability and covalent organic frameworks (COFs) with high stability are promising nanomaterials for electrochemiluminescence (ECL), while Ru-based metal covalent organic frameworks (Ru-MCOFs) have rarely been reported. Herein, an ECL immunosensor based on a strong ECL-emitting Ru-MCOF was proposed for the sensitive detection of the cardiac troponin-I (cTnI). Imine-linked Ru-MCOF was prepared as an ECL emitter via solvothermal method using tris (4,4' -diamino-2,2' -bipyridine) ruthenium (II) (Ru(dbpy)3 2+) as a precursor. Compared with monomers, the imine-linked Ru-MCOF achieved structural extension through covalent bonds, which not only effectively facilitated the electrochemical activation of the luminophores, but also shortened the transmission distance between electrons and co-reactants, generating significant ECL emission. In addition, the porous Ru-MCOF provided a microreactor with nanoconfinement effect, which could accelerate the diffusion of co-reactants into the framework and promote the excitation of internal and external ECL emitters, significantly enhancing the ECL intensity. Considering the excellent ECL performance of Ru-MCOF, combined with dual DNAzymes-driven catalytic hairpin amplification, the ECL immunosensor achieved sensitive detection of cTnI with a detection limit as low as 0.42 fg/mL. The proposed highly stable Ru-MCOF raises a new approach for exploring MCOF-based luminophores, highlighting the potential of MCOFs in advanced ECL emitters.

Emerging electrochemical biosensors for lung cancer-associated protein biomarker and miRNA detection

Lung cancer remains a major driver of global morbidity and mortality, and diagnosing lung tumors early in their development is vital to maximizing treatment efficacy and patient survival. Several biomarkers, including CYFRA 21-1, NSE, ProGRP, CEA, and miRNA, have been identified as reliable indicators for early lung cancer detection and monitoring treatment progress. However, the minute changes in the levels of these biomarkers during the early stages of disease necessitate advanced detection platforms. In this space, electrochemical biosensors have currently emerged as robust tools for early lung cancer screening and diagnosis owing to their low costs, rapid responses, and superior sensitivity and selectivity. This review provides an up-to-date overview of the application of electrochemiluminescence, photoelectrochemical, and other electrochemical analytical strategies for detecting lung cancer-associated protein biomarkers, and miRNA. This review compares these techniques to provide a concise overview of the principles underlying these electrochemical analytical methods, the preparation of their components, and the performance of the resulting biosensors. Lastly, a discussion of the challenges and opportunities associated with electrochemical biosensors detection of lung cancer-associated biomarkers are provided.

A sandwich-type photoelectrochemical biosensor based on anthocyanin-sensitized ZnO/P5FIn heterojunction for the sensitive detection of CYFRA21-1

. A sandwich-type photoelectrochemical (PEC) immunosensor based on a ZnO/poly(5-formylindole) (P5FIn)/anthocyanin heterostructure was developed to achieve sensitive background-free detection of the tumor marker CYFRA21-1. ZnO with good photovoltaic properties is combined with narrow bandgap P5FIn to form a p-n type heterojunction. This structure reduces the electron-hole pair recombination, thereby enhancing the photocurrent response of the composite. Anthocyanidins are environmentally friendly natural compounds with excellent antioxidant, redox properties, and remarkable electrochemical activity. After sensitization by anthocyanins, the absorption and utilization of visible light in the composites are enhanced, further improving the PEC luminescence efficiency of the materials. Additionally, boron nitride quantum dots (BN QDs) are combined with Ab2 via polydopamine (PDA) as a secondary antibody marker, enhancing its sensitivity. The biosensor exhibited a linear detection range of 0.001-100 ng mL-1 with a limit of detection (LOD) of 0.00033 ng mL-1. Furthermore, this biosensor demonstrates excellent selectivity, reproducibility, and stability, as well as successful results in analyzing actual human serum samples. This approach provides a feasible method for tumor marker detection.

A signal amplification electrochemiluminescence biosensor based on Ru(bpy)32+ and β-cyclodextrin for detection of AFP

By combining two different materials, metal-organic frameworks (MOF) and β-cyclodextrins (β-CD), a signal amplification electrochemical luminescence (ECL) immunosensor was constructed to realize the sensitive detection of AFP. The indium-based metal-organic framework (In-MOF) was used as the carrier of Ru(bpy)32+, and Ru(bpy)32+ was immobilized by In-MOF through suitable pore size and electrostatic interaction. At the same time, using host-guest recognition, β-CD enriched TPA into the hydrophobic cavity for accelerating the electronic excitation of TPA, then, achieving the purpose of signal amplification. The signal amplification immunosensor structure is constructed among the primary antibody Ab1 connected to the Ru(bpy)32+@In-MOF modified electrode, AFP, BSA and the secondary antibody (Ab2) loaded with TPA-β-CD. The immunosensor has a good linearity in the range of 10-5 ng/mL-50 ng/mL, and the low limit of detection (LOD) is 1.1 × 10-6 ng/mL. In addition, the electrochemiluminescence immunosensor that we designed has strong stability, good selectivity and repeatability, which provides a choice for the analysis of AFP.

Enhanced Photostability and Photoactivity of Ruthenium Polypyridyl-Based Photocatalysts by Covalently Anchoring Onto Reduced Graphene Oxide

Recentstudies toward finding more efficient ruthenium metalloligands for photocatalysis applications have shown that the derivatives of the linear [Ru(dqp)2]2+ (dqp: 2,6-di(quinolin-8-yl)-pyridine) complexes hold significant promise due to their extended emission lifetime in the μs time scale while retaining comparable redox potential, extinction coefficients, and absorption profile in the visible region to [Ru(bpy)3]2+ (bpy: 2,2'-bipyridine) and [Ru(tpy)2]2+ (tpy: 2,2':6',2″-terpyridine) complexes. Nevertheless, its photostability in aqueous solution needs to be improved for its widespread use in photocatalysis. Carbon-based supports have arisen as potential solutions for improving photostability and photocatalytic activity, yet their effect greatly depends on the interaction of the metal complex with the support. Herein, we present a strategy for obtaining Ru-polypyridyl complexes covalently linked to aminated reduced graphene oxide (rGO) to generate novel materials with long-term photostability and increased photoactivity. Specifically, the hybrid Ru(dqp)@rGO system has shown excellent photostable behavior during 24 h of continual irradiation, with an enhancement of 10 and 15% of photocatalytic dye degradation in comparison with [Ru(dqp)2]2+ and Ru(tpy)@rGO, respectively, as well as remarkable recyclability. The presented strategy corroborates the potential of [Ru(dqp)2]2+ as an interesting photoactive molecule to produce more advantageous light-active materials by covalent attachment onto carbon-based supports.

Highly sensitive biosensor for specific miRNA detection based on cascade signal amplification and magnetic electrochemiluminescence nanoparticles

Herein, magnetic electrochemiluminescence (ECL) nanoparticle Fe3O4@PtPd/Ru(bpy)32+ had been synthesized then been coupled with CRISPR/Cas13a system and Zn2+ dependent DNAzyme to design a novel ECL biosensor for specific detection of microRNA-145 (miRNA). The synthesized multifunctional magnetic nanoluminescent materials Fe3O4@PtPd/Ru(bpy)32+ not only load Ru(bpy)32+ to provide ECL signals, but also can quickly achieve separation and enrichment from complex matrices. In addition, ferrocene (Fc) was used as a quencher in the Ru(bpy)32+/tripropylamine (TPA) system. Fc was modified on DNA bound to Fe3O4@PtPd. Benefited from the highly specific recognition ability of CRISPR/Cas13a, the target miRNA induces CRISPR/Cas13a trans-cleavage to trigger the Zn2+-dependent DNAzyme cyclic cleavage to realize the dual signal amplification. DNA modified by Fc was split by target miRNA-induced cleaving, and then magnetic separation was performed to keep Fc away from the surface of the nanoparticles. Thus, the enhanced ECL signal was obtained to detect miRNA-145. Under optimized conditions, the prepared sensor showed a wide linear range (1 fM to 1 nM) and a low limit of detection (LOD) down to 0.41 fM. Furthermore, it shows excellent selectivity and good reproducibility. The proposed ECL platform has huge potential applications in the development of various sensitive sensors for detecting the other miRNA.

A multiple signal amplification photoelectrochemical biosensor based on biotin-avidin system for kanamycin sensing in fish and milk via synergism of g-C3N4 and Ru@SiO2

BACKGROUND

The residues of kanamycin can accumulate in the human body for a long time and pose serious health risks, including hearing loss, kidney poisoning, and drug allergic reactions. Therefore, it is crucial to develop a rapid, highly sensitive, and low-cost method for detecting kanamycin residues in foods. However, the current methods have limitations such as low sensitivity, expensive instruments, and multiple steps, which make them impractical for use in resource-limited environments and emergencies. In this study, the creation of a multiple-signal amplification photoelectrochemical biosensor to address these aforementioned issues is discussed.

RESULTS

Herein, we proposed a multiple signal amplification photoelectrochemical (PEC) biosensor based on carboxylated g-C3N4 and avidin functionalized Ru@SiO2 for the ultrasensitive detection of kanamycin. The carboxylated g-C3N4 was a highly efficient photoactive substance for amplifying photoelectric signals and a substrate for aptamer immobilization. The DOS and PDOS of g-C3N4 were studied by simulation, and the sensing mechanism of the probe at the molecular level was revealed. Meanwhile, using Ru@SiO2 as a signal amplifying unit, through the cooperative work between Ru@SiO2 and g-C3N4, the photoelectric signal could be double amplified to produce an excellent photocurrent response. Under optimized conditions, the photocurrent response of the PEC biosensor to kanamycin was obtained at concentrations from 0.1 nM to 1000 nM with a lower detection limit of 4.1052 × 10-11 mol L-1. This protocol demonstrates high sensitivity, brilliant specific recognition ability, excellent reproducibility, and acceptable stability.

SIGNIFICANCE

The first combination of g-C3N4 and avidin-Ru@SiO2 as photocurrent materials greatly enhanced the sensitivity of the PEC biosensors. Moreover, the specificity and sensitivity of the PEC biosensor were further improved through the specific interaction between kanamycin and aptamer. The photoelectric conversion mechanism based on g-C3N4 and two pathways for enhancing the photocurrent by Ru(byp)32+ were proposed. Through simulations of the DOS and PDOS of g-C3N4, the sensing mechanism of the probe at the molecular level was revealed. Under the optimum conditions, the PEC biosensor exhibited a wide linear concentration range and a low detection limit.

Metal-organic framework-based platforms for implantation applications: recent advances and challenges

The development of minimally invasive technology has promoted the widespread use of implant interventional materials, which play an important role in alleviating patients' pain during and after surgery. Metal-organic frameworks (MOFs) and their related hybrids formed by bridging ligands and metal nodes via covalent bonds represent one of the smart platforms in implant interventional fields due to their large surface area, adjustable compositions and structures, biodegradability, etc. Significant progresses in the implantation application of MOF-based materials have been achieved recently, but these studies are still in the initial stage. This review highlights the recent advances of MOFs and their related hybrids in orthopedic implantation, cardio-vascular implantation, neural tissue engineering, and biochemical sensing. Each correction between the structural features of MOFs and their corresponding implanted works is highlighted. Finally, the confronting challenges and future perspectives in the implant interventional field are discussed.

CD-MOFs: From preparation to drug delivery and therapeutic application

Cyclodextrin metal-organic frameworks (CD-MOFs) show considerable advantages of edibility, degradability, low toxicity, and high drug loading, which have attracted enormous interest, especially in drug delivery. This review summarizes the typical synthesis approaches of CD-MOFs, the drug loading methods, and the mechanism of encapsulation and release. The influence of the structure of CD-MOFs on their drug encapsulation and release is highlighted. Finally, the challenges CD-MOFs face are discussed regarding biosafety assessment systems, stability in aqueous solution, and metal ion effect.

Detection of CYFRA 21-1 in human serum by an electrochemical immunosensor based on UiO-66-NH2@CMWCNTs and CS@AuNPs

In this study, an electrochemical immunosensor was constructed to detect the cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) in human serum. CYFRA 21-1 is the most sensitive tumor marker of non-small cell lung cancer (NSCLC), its content in normal human serum should be less than 3.3 ng/mL. When lung cancer cells dissolve or die, a myriad of CYFRA 21-1 is released into a tumor patient's blood circulation, and its serum content elevates strikingly. Consequently, detecting CYFRA 21-1 by an electrochemical biosensor is expected to provide a new method for the early detection and prevention of lung cancer. In this study, a composite of UiO-66-NH2 and carboxylated multi-walled carbon nanotubes (CMWCNTs) was used as the substrate material of a sensor; the resulting sensor had a large specific surface area and strong electrical conductivity. Moreover, gold nanoparticles (AuNPs) were used to bind to antibodies through an Au-S bonds. Also, a supersensitive detection of CYFRA 21-1 was achieved through the specific bindings of antigens and antibodies. Under optimal detection conditions, the change of current signal intensity of the immunosensor was proportional to the logarithm of CYFRA 21-1 concentration and had a linear relation in the range of 0.005-400 ng/mL, while the detection limit was 1.15 pg/mL (S/N = 3). The proposed immunosensor had high precision, stability, and selectivity. More importantly, the sensor was been successfully applied to detect CYFRA 21-1 in human serum with high recovery, providing a new method for early screening and dynamic monitoring of lung cancer.

Ultrasensitive Electrochemiluminescence Immunosensor for Bladder Marker Human Complement Factor H-Related Protein Detection

The development of noninvasive and sensitive detection methods for the early diagnosis and monitoring of bladder cancer is critical but challenging. Herein, an ultrasensitive electrochemiluminescence (ECL) immunosensor that uses Ru(bpy)₃²⁺-metal-organic framework (Ru-MOF) nanospheres and a DNA tetrahedral (TDN) probe was established for bladder cancer marker complement factor H-related protein (CFHR1) detection. The synthesized Ru(bpy)₃²⁺-metal-organic frameworks (Ru-MOFs) served as a linked substrate for immobilization of AuNPs and antibody (Ab₂) to prepare the ECL signal probe (Ru-MOF@AuNPs-Ab₂), exhibiting a stable and strengthened ECL emission. At the same time, the inherent advantages of TDN probes on the electrode as the capture probe (TDN-Ab₁) improve the accessibility of targets to probes. In the presence of CFHR1, the signal probe Ru-MOF@AuNPs-Ab₂ was modified on the electrode through immune binding, thereby obtaining an outstanding ECL signal. As expected, the developed ECL immunosensor exhibited splendid performance for CFHR1 detection in the range of 0.1 fg/mL to 10 pg/mL with a quite low detection limit of 0.069 fg/mL. By using the proposed strategy to detect CFHR1 from urine, it showed acceptable accuracy, which can effectively distinguish between bladder cancer patients and healthy samples. This work contributes to a novel, noninvasive, and accurate method for early clinical diagnosis of bladder cancer.

Dual-quenching mechanisms in electrochemiluminescence immunoassay based on zinc-based MOFs of ruthenium hybrid for D-dimer detection

The successful application of electrochemiluminescence (ECL) in immunoassay for clinical diagnosis requires improving sensitivity and accuracy. Herein was reported an ECL analytical model based zinc-based metal-organic frameworks of ruthenium hybrid (RuZn MOFs) as the signal emitter. To enlarge the output difference, the quenching effect of three different noble metal nanoparticles included palladium seeds (Pd_seeds), palladium octahedrons (Pd_oct), and Pt-based palladium (Pd@Pt_oct) core-shell were researched. Among them, Pd@Pt_oct core-shell possessed higher activity and improved durability than Pd-only (NPs), they could load more protein macromolecules amicably and stabilized in the analysis system. Furthermore, since the charge redistribution owing to the hybridization of the Pt and Pd atoms in Pd@Pt_oct, it could generate the electron flow maximumly from the emitter RuZn MOFs to Pd@Pt_oct and result in the enhancement of quenching ECL. And the UV absorption of noble metal nanoparticles overlapped with the ECL emission of RuZn MOFs to varying degrees, which caused the behavior of resonance energy transfer (RET) reaction at the same time. This would greatly promote the sensitivity of this ECL system compared with the traditional single quenching mechanism. Based on this, a signal-off immunsensor was constructed to sensitive detection of D-dimer with linearity range from 0.001 to 200 ng mL^-1, limit of detection (LOD) was 0.20 pg mL^-1 and provide a further theoretical basis for the clinical application of ECL technology.

Electrochemical aptasensor based on the engineered core-shell MOF nanostructures for the detection of tumor antigens

It is essential to develop ultrasensitive biosensors for cancer detection and treatment monitoring. In the development of sensing platforms, metal-organic frameworks (MOFs) have received considerable attention as potential porous crystalline nanostructures. Core-shell MOF nanoparticles (NPs) have shown different diversities, complexities, and biological functionalities, as well as significant electrochemical (EC) properties and potential bio-affinity to aptamers. As a result, the developed core-shell MOF-based aptasensors serve as highly sensitive platforms for sensing cancer biomarkers with an extremely low limit of detection (LOD). This paper aimed to provide an overview of different strategies for improving selectivity, sensitivity, and signal strength of MOF nanostructures. Then, aptamers and aptamers-modified core-shell MOFs were reviewed to address their functionalization and application in biosensing platforms. Additionally, the application of core-shell MOF-assisted EC aptasensors for detection of several tumor antigens such as prostate-specific antigen (PSA), carbohydrate antigen 15-3 (CA15-3), carcinoembryonic antigen (CEA), human epidermal growth factor receptor-2 (HER2), cancer antigen 125 (CA-125), cytokeratin 19 fragment (CYFRA21-1), and other tumor markers were discussed. In conclusion, the present article reviews the advancement of potential biosensing platforms toward the detection of specific cancer biomarkers through the development of core-shell MOFs-based EC aptasensors.

Cyclodextrin-metal-organic frameworks in molecular delivery, detection, separation, and capture: An updated critical review

Metal-organic frameworks (MOFs) are coordination compounds with tuneable structures and controllable functions. However, the biological toxicity of traditional MOFs materials is often inevitable, making their application in the biological field have many limitations. Therefore, frontier research increasingly focuses on developing biocompatible MOFs materials. Cyclodextrins (CDs), derived from starch, are favored by various biomaterials due to their good biosafety and are often seen in the preparation and application of MOFs materials. This review describes the features of MOFs materials, and the various preparation methods of CD-MOFs are analyzed in detail from the perspective of CD classification. Additionally, the promising applications of CD-MOFs materials for delivery, detection, separation, and capture of active molecules in recent studies are systematically discussed and summarized. In terms of safety, the CD-MOFs materials are meticulously summarized. Finally, this review presents the challenges and future prospects regarding the current CD-MOFs-based materials, which will shed new light on the application of such materials in various fields.

ReS2@Au NPs as signal labels quenching steady photocurrent generated by NiCo2O4/CdIn2S4/In2S3 heterojunction for sensitive detection of CYFRA 21-1

In order to achieve rapid and sensitive detection of CYFRA 21-1, a signal-off photoelectrochemical (PEC) immunosensor was devised with NiCo₂O₄/CdIn₂S₄/In₂S₃ heterojunction photoactive materials as sensing platform and ReS₂@Au NPs as the secondary antibody labels amplifying signal based on the energy band-matching cascade structure and double suppression effect. NiCo₂O₄ possessed a faster charge transfer rate due to the abundance of redox electron pairs (Co³⁺/Co²⁺ and Ni³⁺/Ni²⁺). To further improve the PEC properties of NiCo₂O₄ under visible light, CdIn₂S₄ with matching bandgap energy was selected to form heterojunction with NiCo₂O₄ and sensitized with In₂S₃. The proposed heterojunctions with well-matched band structure promoted the transfer of photo-generated carriers and were exploited as signal transducers for immobilization of antibodies and recognition of CYFRA 21-1. Furthermore, a novel urchin-like p-type ReS₂ semiconductor nanostructure functionalized by Au NPs was firstly used as a nanolabel to quench the signal. On the one hand, the Schottky heterojunction generated by ReS₂ and Au NPs could compete with the transducer substrate for both light and electron donors. On the other hand, the large space steric hindrance of ReS₂ prevented contact between the matrix and AA. Subsequently, the sensor was sensitive in a wide range of concentrations for CYFRA 21-1 (0.0001-50 ng/mL), and the detection limit was 0.05 pg/mL.

Blood-based DNA methylation signatures in cancer: A systematic review

DNA methylation profiles are in dynamic equilibrium via the initiation of methylation, maintenance of methylation and demethylation, which control gene expression and chromosome stability. Changes in DNA methylation patterns play important roles in carcinogenesis and primarily manifests as hypomethylation of the entire genome and the hypermethylation of individual loci. These changes may be reflected in blood-based DNA, which provides a non-invasive means for cancer monitoring. Previous blood-based DNA detection objects primarily included circulating tumor DNA/cell-free DNA (ctDNA/cfDNA), circulating tumor cells (CTCs) and exosomes. Researchers gradually found that methylation changes in peripheral blood mononuclear cells (PBMCs) also reflected the presence of tumors. Blood-based DNA methylation is widely used in early diagnosis, prognosis prediction, dynamic monitoring after treatment and other fields of clinical research on cancer. The reversible methylation of genes also makes them important therapeutic targets. The present paper summarizes the changes in DNA methylation in cancer based on existing research and focuses on the characteristics of the detection objects of blood-based DNA, including ctDNA/cfDNA, CTCs, exosomes and PBMCs, and their application in clinical research.

CoNi-RGO and NiCo2S4-ZIF/g-C3N4 signal amplified electrochemical immunosensors for sensitive detection of CYFRA 21-1

Herein, a signal amplified electrochemical immunosensor for the sensitive detection of cytokeratin 19 fragments (CYFRA 21-1) in human serum was discussed. The CoNi-RGO was used as a substrate for the sensor with excellent specific surface area and strong electrical conductivity, which enables more efficient attachment of antibodies. The introduction of the bimetallic sulfide NiCo₂S₄ composite ZIF material provides strong catalytic performance for the immunosensor. It is worth noting that, in addition to these satisfactory advantages, these two materials also show amazing signal amplification capacity. When the immunosensor works, the increase in electrical impedance decreases the electron transfer rate, making the electrochemical signal change obvious. The signal enhancement of immunosensors was emphasized by the marker during construction, and the experimental results were satisfactory. The proposed signal enhanced immunosensor had a linear relationship in the range of 0.001-10 ng/mL for CYFRA 21-1, and the minimum detection limit was 0.33 pg/mL for △I = 95.22 + 23.27 lg c. This demonstrates that the electrochemical immunosensor we constructed is successful and has a great developing potential.

Highly selective molecularly imprinted-electrochemiluminescence sensor based on perovskite/Ru(bpy)32+ for simazine detection in aquatic products

A novel molecularly imprinted electrochemiluminescence (MIECL) sensor based on the luminescence of molecularly imprinted polymer-perovskite (MIP-CsPbBr₃) layer and Ru(bpy)₃²⁺ was fabricated for simazine detection. MIP-CsPbBr₃ layers were immobilized onto the surface of glassy carbon electrode as the capture and signal amplification probe, and Ru(bpy)₃²⁺ and co-reactant tripropylamine exhibited stronger electrochemiluminescence (ECL) emission. Under optimal conditions, the ECL signal of the MIECL sensor was linearly quenched, with the logarithm of simazine concentration ranging from 0.1 μg/L to 500.0 μg/L, correlation coefficient of 0.9947, and limit of detection of 0.06 μg/L. The practicality of the developed MIECL sensor method for simazine determination in aquatic samples was validated. Excellent recoveries of 86.5 %-103.9 % with relative standard deviation below 1.6 % were obtained for fish and shrimp samples at three different spiked concentrations. The MIECL sensor exhibited excellent selectivity, sensitivity, reproducibility, accuracy, and precision for simazine determination in actual aquatic samples.

Synthesis and potential applications of cyclodextrin-based metal-organic frameworks: a review

Metal-organic frameworks are porous polymeric materials formed by linking metal ions with organic bridging ligands. Metal-organic frameworks are used as sensors, catalysts for organic transformations, biomass conversion, photovoltaics, electrochemical applications, gas storage and separation, and photocatalysis. Nonetheless, many actual metal-organic frameworks present limitations such as toxicity of preparation reagents and components, which make frameworks unusable for food and pharmaceutical applications. Here, we review the structure, synthesis and properties of cyclodextrin-based metal-organic frameworks that could be used in bioapplications. Synthetic methods include vapor diffusion, microwave-assisted, hydro/solvothermal, and ultrasound techniques. The vapor diffusion method can produce cyclodextrin-based metal-organic framework crystals with particle sizes ranging from 200 nm to 400 μm. Applications comprise food packaging, drug delivery, sensors, adsorbents, gas separation, and membranes. Cyclodextrin-based metal-organic frameworks showed loading efficacy of the bioactive compounds ranging from 3.29 to 97.80%.

Dual-Mechanism Quenching of Electrochemiluminescence Immunosensor Based on a Novel ECL Emitter Polyoxomolybdate-Zirconia for 17β-Estradiol Detection

The exploration of novel electrochemiluminescence (ECL) reagents has been a breakthrough work in ECL immunoassay. In this work, the ECL properties of polyoxomolybdate-zirconia (POM-ZrO₂) were discovered for the first time and their luminescence mechanism was initially explored. Virgulate POM-ZrO₂ was synthesized from phosphomolybdic acid hydrate and zirconium oxychloride by solvothermal method, which achieved intense and stabilized cathode ECL emission at a negative potential. Polyaniline@Au nanocrystals (PANI@AuNPs) as the executor of the dual-mechanism quenching strategy were used to reduce the output signal. The quenching efficiency was significantly enhanced by the dual mechanisms of ECL energy transfer and electron transfer. Specifically, PANI@AuNPs can serve as an energy receptor to absorb the energy emitted by POM-ZrO₂ (energy donor), while the appropriate energy level can be regarded as the condition for electron transfer to quench the ECL intensity of POM-ZrO₂. Herein, the proposed dual-mechanism quenching strategy was applied to the immunoassay of 17β-estradiol by constructing a competitive immunosensor. As expected, the immunosensor demonstrated favorable analytical performance and a wide sensing range from 0.01 pg/mL to 200 ng/mL. Hence, it provides a novel method for the sensitive analysis of other biomolecules, such as disease markers and environmental estrogens.

Detection of CYFRA21-1 in serum by electrochemical immunosensor based on nanocomposite consisting of AuNPs@CMK-3@CMWCNTs

An electrochemical immunosensor based on the modification of nanocomposite was constructed to detect the lung cancer marker Cytokeratin 19 fragment antigen 21-1 (CYFRA21-1). Ordered mesoporous carbon CMK-3 was selected to mix with carboxylated multi-walled carbon nanotubes (CMWCNTs), and their combination could enhance electron transfer efficiency and amplify the electrochemical signal. Furthermore, aurum nanoparticles (AuNPs) were further mixed with the hybrid carbon nanomaterials, which bind antibodies via Au-S bonds and provide numerous of binding sites for antibodies. Finally, CYFRA21-1 could be detected by specific immune response between antigen and antibody by improving the immunosensor sensitivity. The characterization of scanning electron microscopy (SEM) showed that AuNPs were embedded on the surface and interstices of CMK-3@CMWCNTs. The curves of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that the immunsensor was successfully constructed. The constructed immunosensor had a linear range of 0.5 pg/mL to 10⁵ pg/mL for the detection of CYFRA21-1 in serum, and the correlation coefficient (r) was 0.998, with a detection limit of 0.2 pg/mL. Thus, this method is selective and sensitive for getting the accurate and reliable detection results and provides a new method for the CYFRA21-1 ultrasensitive detection in serum.

Metal-organic frameworks as a therapeutic strategy for lung diseases

Lung diseases remain a global burden today. Lower respiratory tract infections alone cause more than 3 million deaths worldwide each year and are on the rise every year. In particular, with coronavirus disease raging worldwide since 2019, we urgently require a treatment for lung disease. Metal organic frameworks (MOFs) have a broad application prospect in the biomedical field due to their remarkable properties. The unique properties of MOFs allow them to be applied as delivery materials for different drugs; diversified structural design endows MOFs with diverse functions; and they can be designed as various MOF-drug synergistic systems. This review concentrates on the synthesis design and applications of MOF based drugs against lung diseases, and discusses the possibility of preparing MOF-based inhalable formulations. Finally, we discuss the chances and challenges of using MOFs for targeting lung diseases in clinical practice.

Cyclodextrin metal-organic frameworks and derivatives: recent developments and applications

While there is a tremendous amount of scientific research on metal organic frameworks (MOFs) for gas storage/separation, catalysis and energy storage, the development and application of biocompatible MOFs still poses major challenges. In general, they can be synthesised from various biocompatible linkers and metal ions but particularly cyclodextrins (CDs) as cyclic oligosaccharides are an astute choice for the former. Although the field of CD-MOF materials is still in the early stages and their design and fabrication comes with many hurdles, the benefits coming from CDs built in a porous framework are exciting. Versatile host-guest complexation abilities, high encapsulation capacity and hydrophilicity are among the valuable properties inherent to CDs and offer extended and novel applications to MOFs. In this review, we provide an overview of the state-of-the-art synthesis, design, properties and applications of these materials. Initially, a rationale for the preparation of CD-based MOFs is provided, based on the chemical and structural properties of CDs and including their advantages and disadvantages. Further on, the review exhaustively surveys CD-MOF based materials by categorising them into three sub-classes, namely (i) CD-MOFs, (ii) CD-MOF hybrids, obtained via combination with external materials, and (iii) CD-MOF-derived materials prepared under pyrolytic conditions. Subsequently, CD-based MOFs in practical applications, such as drug delivery and cancer therapy, sensors, gas storage, (enantiomer) separations, electrical devices, food industry, and agriculture, are discussed. We conclude by summarizing the state of the art in the field and highlighting some promising future developments of CD-MOFs.

Copper-Doped Terbium Luminescent Metal Organic Framework as an Emitter and a Co-reaction Promoter for Amplified Electrochemiluminescence Immunoassay

This work designed a signal amplification strategy for construction of a highly sensitive electrochemiluminescence (ECL) biosensor by doping Cu²⁺ in a terbium luminescent metal organic framework (Cu:Tb-MOF) to act as a co-reaction promoter, which enhanced the generation of SO₄^•- radical during the cathodic process in the presence of K₂S₂O₈ as a co-reactant. The porous and hollow morphology and the size of Cu:Tb-MOF could be efficiently tuned via changing the molar ratio of Cu²⁺ and Tb³⁺ and the reaction time, which were related to the specific surface area, pore diameter, and the ECL intensity of the MOF structure. To further improve the sensitivity of the ECL biosensor, H₂O₂ was introduced into the ECL system to act as another co-reaction promoter, leading to a new ECL mechanism involving dual co-reaction promoters. In view of the low electron transfer resistance of Cu:Tb-MOF, a label-free ECL immunosensor was conveniently constructed by co-immobilizing Cu:Tb-MOF and the capture antibody on the electrode surface. Using pro-gastrin-releasing peptide (ProGRP, a biomarker of small-cell lung cancer) as the model target, the proposed immunosensor exhibited excellent performance with a detection range of 1.0 pg·mL^-1 to 50 ng·mL^-1 and a limit of detection down to 0.68 pg·mL^-1 (3σ). This work demonstrated a strategy to use the MOF structures as both an emitter and a co-reaction promoter for amplified ECL emission and proposed an innovative route to extend the application of lanthanide MOFs.

Liquid Biopsy-Based Biosensors for MRD Detection and Treatment Monitoring in Non-Small Cell Lung Cancer (NSCLC)

Globally, non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths. Despite advancements in chemotherapy and targeted therapies, the 5-year survival rate has remained at 16% for the past forty years. Minimal residual disease (MRD) is described as the existence of either isolated tumour cells or circulating tumour cells in biological liquid of patients after removal of the primary tumour without any clinical signs of cancer. Recently, liquid biopsy has been promising as a non-invasive method of disease monitoring and treatment guidelines as an MRD marker. Liquid biopsy could be used to detect and assess earlier stages of NSCLC, post-treatment MRD, resistance to targeted therapies, immune checkpoint inhibitors (ICIs) and tumour mutational burden. MRD surveillance has been proposed as a potential marker for lung cancer relapse. Principally, biosensors provide the quantitative analysis of various materials by converting biological functions into quantifiable signals. Biosensors are usually operated to detect antibodies, enzymes, DNA, RNA, extracellular vesicles (EVs) and whole cells. Here, we present a category of biosensors based on the signal transduction method for identifying biosensor-based biomarkers in liquid biopsy specimens to monitor lung cancer treatment.