A novel electrochemiluminescence aptasensor based CdTe QDs@NH2-MIL-88(Fe) for signal amplification

Simultaneous Detection of Micro-RNAs by a Disposable Biosensor via the Click Chemistry Connection Strategy

Simultaneous detection of multiple breast cancer-associated miRNAs significantly raises the accuracy and reliability of early diagnosis. In this work, disposable carbon fiber paper serves as the biosensing interface, linking DNA probes via click chemistry to efficiently capture targets and signals efficiently. DNA probes have multiple recognition domains that trigger a cascade reaction through the helper probes and targets, resulting in two signals output. The signals are centrally encapsulated in the pore of the MIL-88(Fe)-NH2. The signal carriers are directed by signal probes to the recognition domains that correspond to the DNA probes. The biosensor is selective and stable, and it can quantify miRNA-21 and miRNA-155 simultaneously with detection limits of 0.64 and 0.54 fmol/L, respectively. Furthermore, it demonstrates satisfactory performance in tests conducted with normal human serum and cell lysate. Overall, this method makes a satisfactory exploration to realize an inexpensive and sensitive biosensor for multiple biomarkers.

A molecule-imprinted electrochemiluminescence sensor based on CdS@MWCNTs for ultrasensitive detection of fenpropathrin

A molecularly-imprinted electrochemiluminescence sensor was constructed for the determination of fenpropathrin (FPT) by molecular imprinting technology. In this sensing platform, the introduction of CdS@MWCNTs significantly enhanced the initial ECL signal of the luminol-O2 system. Specifically, MWCNTs was used as a carrier to adsorb more CdS, in which CdS acted as a co-reaction promoter for luminescence. Molecularly imprinted polymer (MIP) containing specific recognition sites of FPT was used as the material for selective recognition. With increasing amount of FPT the ECL signal decreased. Under the optimum conditions, the ECL response was linearly related to the logarithm of FPT concentration. The developed ECL sensor allowed for sensitive determination of FPT and exhibited a wide linear range from 1.0 × 10- 10 mol L- 1 to 1.0 × 10- 6 mol L- 1. The limit of detection was 3.3 × 10- 11 mol L- 1 (S/N = 3). It can be used for the detection of FPT in vegetable samples.

An electrochemiluminescence sensor based on the CNTs and CdSe@ZnSe for determination of melamine in milk samples

In this work, a novel electrochemiluminescence (ECL) sensor based on the CdSe@ZnSe and CNTs was constructed for the detection of melamine. CdSe@ZnSe acted as the co-reaction promoter for the enhancement of Ru(bpy)32+/tri-n-propylamine (TPrA) system and CNTs acted as carriers to immobilize more CdSe@ZnSe. The initial ECL signal significantly amplified due to the synergistic effect of CNTs and CdSe@ZnSe. The ECL signal decreased with the addition of melamine, and the change value of ECL intensity (ΔI) was linearly related to the logarithm of melamine concentration. The constructed ECL sensor was able to detect melamine in the range of 1.0 × 10-11 - 1.0 × 10-7 M, and the detection limit was 3.3 × 10-12 M (S/N = 3). It can be used to detect melamine in milk samples.

Advancements in nanomaterial-based aptasensors for the detection of emerging organic pollutants in environmental and biological samples

The combination of nanomaterials (NMs) and aptamers into aptasensors enables highly specific and sensitive detection of diverse pollutants. The great potential of aptasensors is recognized for the detection of diverse emerging organic pollutants (EOPs) in different environmental and biological matrices. In addition to high sensitivity and selectivity, NM-based aptasensors have many other advantages such as portability, miniaturization, facile use, and affordability. This work showcases the recent advances achieved in the design and fabrication of NM-based aptasensors for monitoring EOPs (e.g., hormones, phenolic contaminants, pesticides, and pharmaceuticals). On the basis of their sensing mechanisms, the covered aptasensing systems are classified as electrochemical, colorimetric, PEC, fluorescence, SERS, and ECL. Special attention has been paid to the fabrication processes, analytical achievements, and sensing mechanisms of NM-based aptasensors. Further, the practical utility of aptasensing approaches has also been assessed based on their basic performance metrics (e.g., detection limits, sensing ranges, and response times).

A comprehensive review on electrochemical and optical aptasensors for organophosphorus pesticides

There has been a rise in pesticide use as a result of the growing industrialization of agriculture. Organophosphorus pesticides have been widely applied as agricultural and domestic pest control agents for nearly five decades, and they remain as health and environmental hazards in water supplies, vegetables, fruits, and processed foods causing serious foodborne illness. Thus, the rapid and reliable detection of these harmful organophosphorus toxins with excellent sensitivity and selectivity is of utmost importance. Aptasensors are biosensors based on aptamers, which exhibit exceptional recognition capability for a variety of targets. Aptasensors offer numerous advantages over conventional approaches, including increased sensitivity, selectivity, design flexibility, and cost-effectiveness. As a result, interest in developing aptasensors continues to expand. This paper discusses the historical and modern advancements of aptasensors through the use of nanotechnology to enhance the signal, resulting in high sensitivity and detection accuracy. More importantly, this review summarizes the principles and strategies underlying different organophosphorus aptasensors, including electrochemical, electrochemiluminescent, fluorescent, and colorimetric ones.

Metal organic frameworks as advanced functional materials for aptasensor design

BACKGROUND

Advancement in coordination chemistry has achieved an impressive development of metal organic frameworks (MOFs) as the supramolecular hybrid materials, comprising harmonized metal nodes with organic ligands. Scope and approach: MOFs offer the unique properties of easy synthesis, nanoscale structure, adjustable size and morphology, high porosity, large surface area, supreme chemical tunability and stability, and biocompatibility. The features provide an exceptional opportunity for the widely usage of MOFs in the different scientific fields, e.g. biomedicine, electrocatalysis, food safety, energy storage, environmental surveillance, and biosensing platforms. The synergistic incorporation of the aptamer advantages and the superiorities of MOFs attains the novel MOF-based aptasensors. The excellent selectivity and sensitivity of the MOF-based aptasensors nominate them as efficient lab-on-chip tools for cost-effective, label-free, portable, and real-time monitoring of diverse targets.

KEY FINDINGS AND CONCLUSIONS

Here, we review the achievements in the sensor design by cooperation of MOF motifs and aptamers with the conspicuous potential of determining the targets. Finally, some results are expressed that provide a valuable viewpoint for developing the novel MOF-based test strips in the future.

Effective Electrochemiluminescence Aptasensor for Detection of Atrazine Residue

According to the chemiluminescence characteristics of the luminol-hydrogen peroxide (H₂O₂) system, this work designed a novel and effective electrochemiluminescence (ECL) aptasensor to detect atrazine (ATZ) rapidly. Silver nanoparticles (AgNPs) could effectively catalyze the decomposition of H₂O₂ and enhance the ECL intensity of the luminol-H₂O₂ system. Once ATZ was modified on the aptasensor, the ECL intensity was significantly weakened because of the specific combination between ATZ and its aptamer. Therefore, the changes in ECL intensity could be used to detect the concentration of ATZ. Under optimal detecting conditions, the aptasensor had a wide linear range from 1 × 10⁻³ ng/mL to 1 × 10³ ng/mL and a low limit of detection (3.3 × 10⁻⁴ ng/mL). The designed aptasensor had the advantages of good stability, reproducibility, and specificity. The aptasensor could be used to detect the ATZ content of tap water, soil, and cabbage and had satisfactory results. This work effectively constructs a novel, effective, and rapid ECL aptasensor for detecting ATZ in actual samples.

Electrochemical (Bio)Sensors for the Detection of Organophosphorus Pesticides Based on Nanomaterial-Modified Electrodes: A Review

Organophosphorus pesticides were easily remained in fruits and vegetables which would be harm to the environmental safety and human health. In recent years, due to the simple preparation process, fast response and high sensitivity, the electrochemical (bio)sensors have received increasing attention, which were extensively used as the sensing platform for the detection of OPPs. The mechanisms for the determination of OPPs mainly included redox of nitrophenyl OPPs, enzyme hydrolysis and inhibition, immunosensor, aptasensor. Nowadays, the mainly explored electrode material has focused on metal-organic frameworks, metal and metal derivatives, carbon materials (carbon nanotube, graphene, g-C3N4), MXene, etc. These nanomaterials played important roles in the electrochemical (bio)sensors, which included: (a) as an electrocatalyst to promote the redox reaction, (b) as a carrier to load the enzyme or aptamer, (c) as a recognizer to identify the targets. The nanomaterials-based electrochemical (bio)sensor was a rapid, cost-effective methods to detect OPPs with high sensitivity. Besides, this review compared the analytical performance of different nanomaterials-based electrochemical (bio)sensors, and also identified the key challenges in the future. It would provide new ideas and insights to the further development and application of electrochemical (bio)sensors and the detection of pesticides in real samples.

Signal enhancing strategies in aptasensors for the detection of small molecular contaminants by nanomaterials and nucleic acid amplification

Small molecular contaminants (such as mycotoxins, antibiotics, pesticide residues, etc.) in food and environment have given rise to many biological and ecological toxicities, which has attracted worldwide attention in recent years. Meanwhile, due to the advantages of aptamers such as high specificity and stability, easy synthesis and modification, as well as low cost and immunogenicity, various aptasensors for the detection of small molecular contaminants have been flourishing. An aptasensor as a whole is composed of an aptamer-based target recognizer and a signal transducer, which are fields of concentrated research. In the practical detection applications, in order to achieve the quantitative detection of small molecular contaminants at low abundance in real samples, a large number of signal enhancing strategies have been utilized in the development of aptasensors. Recent years is a vintage period for efficient signal enhancing strategies of aptasensors by the aid of nanomaterials and nucleic acid amplification that are applied in the elements for target recognition and signal conversion. Therefore, this paper meticulously reviews the signal enhancing strategies based on nanomaterials (including the (quasi-)zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanomaterials) and nucleic acid amplification (including enzyme-assisted nucleic acid amplification and enzyme-free nucleic acid amplification). Furthermore, the challenges and future trends of the abovementioned signal enhancing strategies for application are also discussed in order to inspire the practitioners in the research and development of aptasensors for small molecular contaminants.

Functionalized MOF PCN-222-loaded quantum dots as an electrochemiluminescence sensing platform for the sensitive detection of p-nitrophenol

The composite PCN-222@CdSe was used to detect PNP.

Highly efficient peroxidase-like activity of a metal–oxide-incorporated CeO2–MIL(Fe) metal–organic framework and its application in the colorimetric detection of melamine and mercury ions via induced hydrogen and covalent bonds

The illegal addition of melamine to dairy products and the contamination of water with Hg2+ are serious threats to human health. This necessitates the search for new and efficient probe for detection of melamine in foods and Hg2+ in water samples.

Dual fluorometric biosensor based on a nanoceria encapsulated metal organic framework and a signal amplification strategy of a hybridization chain reaction for the detection of melamine and Pb2+ ions in food samples

The increased need for melamine and Pb2+ ion detection systems that are versatile, ultra-sensitive, and easy to use is highly significant.

A Novel Photoelectrochemical Aptamer Sensor Based on CdTe Quantum Dots Enhancement and Exonuclease I-Assisted Signal Amplification for Listeria monocytogenes Detection

To achieve the rapid detection of Listeria monocytogenes, this study used aptamers for the original identification and built a photoelectrochemical aptamer sensor using exonuclease-assisted amplification. Tungsten trioxide (WO3) was used as a photosensitive material, was modified with gold nanoparticles to immobilize complementary DNA, and amplified the signal by means of the sensitization effect of CdTe quantum dots and the shearing effect of Exonuclease I (Exo I) to achieve high-sensitivity detection. This strategy had a detection limit of 45 CFU/mL in the concentration range of 1.3 × 101-1.3 × 107 CFU/mL. The construction strategy provides a new way to detect Listeria monocytogenes.

Reactive oxygen species trigger NF-κB-mediated NLRP3 inflammasome activation involvement in low-dose CdTe QDs exposure-induced hepatotoxicity

Cadmium telluride (CdTe) quantum dots (QDs) can be employed as imaging and drug delivery tools; however, the toxic effects and mechanisms of low-dose exposure are unclear. Therefore, this pioneering study focused on hepatic macrophages (Kupffer cells, KCs) and explored the potential damage process induced by exposure to low-dose CdTe QDs. In vivo results showed that both 2.5 μM/kg·bw and 10 μM/kg·bw could both activate KCs to cause liver injury, and produce inflammation by disturbing antioxidant levels. Abnormal liver function further verified the risks of low-dose exposure to CdTe QDs. The KC model demonstrated that low-dose CdTe QDs (0 nM, 5 nM and 50 nM) can be absorbed by cells and cause severe reactive oxygen species (ROS) production, oxidative stress, and inflammation. Additionally, the expression of NF-κB, caspase-1, and NLRP3 were decreased after pretreatment with ROS scavenging agent N-acetylcysteine (NAC, 5 mM pretreated for 2 h) and the NF-κB nuclear translocation inhibitor Dehydroxymethylepoxyquinomicin (DHMEQ, 10 μg/mL pretreatment for 4 h) respectively. The results indicate that the activation of the NF-κB pathway by ROS not only directly promotes the expression of inflammatory factors such as pro-IL-1β, TNF-α, and IL-6, but also mediates the assembly of NLRP3 by ROS activation of NF-κB pathway, which indirectly promotes the expression of NLRP3. Finally, a high-degree of overlap between the expression of the NF-κB and NLRP3 and the activated regions of KCs, further support the importance of KCs in inflammation induced by low-dose CdTe QDs.

Deployment of MIL-88B(Fe)/TiO2 Nanotube-Supported Ti Wires as Reusable Electrochemiluminescence Microelectrodes for Noninvasive Sensing of H2O2 from Single Cancer Cells

As one of the significant intracellular signaling molecules, hydrogen peroxide (H₂O₂) regulates some vital biological processes. However, it remains a challenge to develop noninvasive electrodes that can be used for sensing trace H₂O₂ at the cellular level. Here, we evaluated a high-performance solid-state electrochemiluminescence (ECL) H₂O₂ sensor based on MIL-88B(Fe) nanocrystal-anchored Ti microwires. Semiconducting TiO₂ nanotubes (TiNTs) vertically grown around a Ti wire via an anodization technique act as an intrinsic ECL luminophore. By integrating with MIL-88B(Fe), the synergistic effect of the TiO₂ luminophore and the remarkable peroxidase-like activity of MIL-88B(Fe) enable the resulting H₂O₂ sensor an ultrahigh sensitivity featuring a minimum detection limit of 0.1 nM (S/N = 3), long-term stability, high durativity, and wide-range linear response to a concentration of up to 10 mM. To demonstrate the concept of a MIL-88B(Fe)@TiO₂ microelectrode for single-cell sensing, the electrode was used to detect intracellular H₂O₂ in a single cell. Moreover, benefiting from the heterojunction of MIL-88B(Fe)/TiO₂, the microelectrode was found to exhibit excellent photocatalytic activity in the visible-light range, that is, the sensor surface can be self-cleaning after a short visible-light treatment. These advanced sensor characteristics involving easy reusability reveal that the MIL-88B(Fe)@TiO₂ microelectrode is a new platform for cytosensing. This study provides a new strategy to design semiconductor materials with arbitrary shape and size, allowing for profound applications in biomedical and clinical analysis.

Efficient preparation of dual-emission ratiometric fluorescence sensor system based on aptamer-composite and detection of bis(2-ethylhexyl) phthalate in pork

A ratiometric fluorescence sensor system is proposed for detecting bis(2-ethylhexyl) phthalate (DEHP) in pork, which is based on aptamer recognition with molybdenum disulfide quantum dots and cadmium telluride quantum dots (MoS₂ QDs/CdTe-Apta). Two signals exist in the system, among which the response signal is transmitted by CdTe-Apta. The amide condensation between aptamers and CdTe QDs shortens the distance between CdTe QDs and DEHP, thus quenching the fluorescence of CdTe QDs, possibly through a photoinduced electron transfer mechanism. The MoS₂ QDs deliver the self-calibration signal, and the fluorescence of MoS₂ QDs remains almost constant when co-existing with DEHP. Linearity (R² = 0.9536) was established for the DEHP concentration range 0.005-3.0 mg·L^-1, with a limit of detection of 0.21 μg·L^-1. The system was successfully applied in the determination of DEHP in pork. The system has potential for the quantitative determination of DEHP in practical applications.

A novel heterogeneous catalyst NH2-MIL-88/PMo10V2 for the photocatalytic activity enhancement of benzene hydroxylation

In this work, heterogeneous catalyst NH2-MIL-88/PMo10V2-3 has shown the high hydroxylation activity of benzene under visible light (a 5 W LED), which mainly attributed to the production of hydroxyl radical(˙OH) and V5+/V4+ redox pair in the existence of electron (e−).