Enzyme-induced multicolor colorimetric and electrochemiluminescence sensor with a smartphone for visual and selective detection of Hg2

Maternal exposure to ZIF-8 derails placental function by inducing trophoblast pyroptosis through neutrophils activation in mice

Adverse environmental factors during maternal gestation pose a threat to pregnancy. Environmental factors, particularly nanoparticles, can impact pregnancy by causing damage to the placenta. Compared to early gestation, foetuses in late gestation are more robustly developed and at lower risk of adverse effects from environmental factors. Delivery systems for targeted therapy during pregnancy is predominantly focused on their application in late gestation. Zeolitic imidazolate framework-8 (ZIF-8) holds great potential for targeted drug therapy. To evaluate the value of ZIF-8 in targeted treatment of disorders associated with late gestation, it is crucial to investigate the biological effects of ZIF-8 exposure during late gestation. Here, a mouse model exposed to ZIF-8 particles at different doses (5, 10, and 15 mg/kg) during late gestation was constructed. We found that ZIF-8 particles were deposited in the uterus of pregnant mice. ZIF-8 could trigger placental neutrophil aggregation and induce inflammation, which led to trophoblast pyroptosis and impair placental function, adversely affecting the foetus. Neutrophil depletion alleviated placental and foetal damage induced by ZIF-8. This study provides a novel mechanistic view of the reproductive toxicity induced by ZIF-8 and may offer clues to reduce the latent harm of adverse environmental factors to pregnancy.

Colorimetric detection of Hg2+ based on the enhanced oxidase-mimic activity of CuO/Au@Cu3(BTC)2 triggered by Hg2

It is imperative to develop a rapid detection method for Hg2+ due to its harm to human health and the ecological environment. In this research, CuO/Au@Cu3(BTC)2 was synthesized through reducing HAuCl4 by CuxO@Cu3(BTC)2, which was obtained by reducing Cu3(BTC)2 with hydrazine hydrate. The oxidase-mimic activity of CuO/Au@Cu3(BTC)2 can be enhanced by Hg2+ through forming a Au-Hg alloy. Therefore, a colorimetric method was designed for Hg2+ detection with a linear relationship in the 0.05-25 μM range and a limit of detection of 9.7 nM. This strategy exhibited a strong selectivity to Hg2+ and was applied in a real water sample with reliable recoveries. This work provides a possibility for the rapid detection of Hg2+.

Label-free fluorescence detection of mercury ions based on thymine-mercury-thymine structure and CRISPR-Cas12a

In this work, we developed a novel label-free fluorescent sensor for the highly sensitive detection of mercury ions (Hg2+) based on the coordination chemistry of thymine-Hg2+-thymine (T-Hg2+-T) structures and the properties of CRISPR-Cas12a systems. Most notably, two T-rich sequences (a blocker and an activator) were designed to form stable double-stranded structures in the presence of Hg2+ via the T-Hg2+-T base pairing. The formation of T-T mismatched double-stranded DNA between the blocker and the activator prevented the cleavage of G-rich sequences by Cas12a, allowing them to fold into G-quadruplex-thioflavin T complexes, resulting in significantly enhanced fluorescence. Under the optimized conditions, the developed sensor showed an excellent response for Hg2+ detection in the linear range of 0.05 to 200 nM with a detection limit of 23 pM. Moreover, this fluorescent sensor exhibited excellent selectivity and was successfully used for the detection of Hg2+ in real samples of Zhujiang river water and tangerine peel, demonstrating its potential in environmental monitoring and food safety applications.

Multi-modal nanoprobe-enabled biosensing platforms: a critical review

Nanomaterials show great potential for applications in biosensing due to their unique physical, chemical, and biological properties. However, the single-modal signal sensing mechanism greatly limits the development of single-modal nanoprobes and their related sensors. Multi-modal nanoprobes can realize the output of fluorescence, colorimetric, electrochemical, and magnetic signals through composite nanomaterials, which can effectively compensate for the defects of single-modal nanoprobes. Following the multi-modal nanoprobes, multi-modal biosensors break through the performance limitation of the current single-modal signal and realize multi-modal signal reading. Herein, the current status and classification of multi-modal nanoprobes are provided. Moreover, the multi-modal signal sensing mechanisms and the working principle of multi-modal biosensing platforms are discussed in detail. We also focus on the applications in pharmaceutical detection, food and environmental fields. Finally, we highlight this field's challenges and development prospects to create potential enlightenment.

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.

Smartphone-based pH responsive 3-channel colorimetric biosensor for non-enzymatic multi-antibiotic residues

Antibiotic residues in animal-derived food pose a risk to food safety and human health. Here, a smartphone-based pH-responsive 3-channel colorimetric biosensor is constructed for rapid detection of non-enzymatic multi-antibiotic residues in milk. In this system, a magnetic separation and enrichment approach is designed to specifically capture different antibiotic residues in complex environment. Indicators loaded on polydopamine-silver nanoparticles with excellently pH responsive visualization properties are utilized to ensure the high sensitivity of detection system. Moreover, smartphones are introduced to fulfill the demand for portable and on-site inspection of practical applications. It achieves simultaneous detection of oxytetracycline, kanamycin and streptomycin in the linear range of 1-105 pg/mL with detection limits of 0.085, 0.168, and 0.307 pg/mL, respectively. The practicality of the reported multi-antibiotic residues detection system is successfully demonstrated and evaluated challenging milk samples. Therefore, this system demonstrates the wide applications in multi-antibiotic residue analysis and food safety guarantee.

Highly stable Ru-complex-based metal-covalent organic frameworks as novel type of electrochemiluminescence emitters for ultrasensitive biosensing

Developing novel types of high-performance electrochemiluminescence (ECL) emitters is of great significance for constructing ultrasensitive ECL sensors. Herein, a highly stable metal-covalent organic framework (MCOF), termed Ru-MCOF, has been devised and synthesized by employing a classic ECL luminophore, tris(4,4'-dicarboxylicacid-2,2'-bipyridyl)ruthenium(II) (Ru(dcbpy)₃²⁺), as building unit and applied as a novel ECL probe to construct an ultrasensitive ECL sensor for the first time. Impressively, the topologically ordered and porous architectures of the Ru-MCOF not only allow Ru(bpy)₃²⁺ units to precisely locate and homogeneously distribute in the skeleton via strong covalent bonds but also facilitate the transport of co-reactants and electrons/ions in channels to promote the electrochemical activation of both external and internal Ru(bpy)₃²⁺ units. All these features endow the Ru-MCOF with excellent ECL emission, high ECL efficiency, and outstanding chemical stability. As expected, the constructed ECL biosensor based on the Ru-MCOF as a high-efficiency ECL probe accomplishes the ultrasensitive detection of microRNA-155. Overall, the synthesized Ru-MCOF not only enriches the MCOF family but also displays excellent ECL performance and thus expands the application of MCOFs in bioassays. Considering the structural diversity and tailorability of MCOFs, this work opens a new horizon to design and synthesize high-performance ECL emitters, therefore paving a new way to develop highly stable and ultrasensitive ECL sensors and motivating further research on MCOFs.

Gold nanocluster-confined covalent organic frameworks as bifunctional probes for electrochemiluminescence and colorimetric dual-response sensing of Pb2

The development of bifunctional signal probes based on a single component is highly desirable for sensitive and simple dual-mode detection of Pb²⁺. Here, novel gold nanocluster-confined covalent organic frameworks (AuNCs@COFs) were fabricated as a bisignal generator to enable electrochemiluminescence (ECL) and colorimetric dual-response sensing. AuNCs with both intrinsic ECL and peroxidase-like activity were confined into the ultrasmall pores of the COFs via an in situ growth method. On the one hand, the space-confinement effect of the COFs closed the ligand motion-induced nonradiative transition channels of the AuNCs. As a result, the AuNCs@COFs exhibited a 3.3-fold enhancement in anodic ECL efficiency compared to the solid-state aggregated AuNCs using triethylamine as the coreactant. On the other hand, due to the outstanding spatial dispersibility of the AuNCs in the structurally ordered COFs, a high density of active catalytic sites and accelerated electron transfer were obtained, leading to the promotion of the enzyme-like catalytic capacity of the composite. To validate its practical applicability, a Pb²⁺-triggered dual-response sensing system was proposed based on the aptamer-regulated ECL and peroxidase-like activity of the AuNCs@COFs. Sensitive determinations down to 7.9 pM for the ECL mode and 0.56 nM for the colorimetric mode were obtained. This work provides an approach for designing single element-based bifunctional signal probes for dual-mode detection of Pb²⁺.

Logic-Gates of Gas Pressure for Portable, Intelligent and Multiple Analysis of Metal Ions

DNA logic gates have shown outstanding magic in intelligent biology applications, but it remains challenging to construct a portable, affordable and convenient DNA logic gate. Herein, logic gates of gas pressure were innovatively developed for multiplex analysis of metal ions. Hg²⁺ and Ag⁺ were input to interact specifically with the respective mismatched base pairs, which activated DNA extension reaction by polymerase and led to the enrichment of platinum nanoparticles for catalyzing the decomposition of peroxide hydrogen. Thus, the gas pressure obtained from a sealed well was used as output for detecting or identifying metal ions. Hg²⁺ and Ag⁺ were sensitively and selectively detected, and the assay of the real samples was also satisfactory. Based on this, DNA logic gates, including YES, NOT, AND, OR, NAND, NOR, INHIBIT, and XOR were successfully established using a portable and hand-held gas pressure meter as detector. So, the interactions between DNA and metal ions were intelligently transferred into the output of gas pressure, which made metal ions to be detected portably and identified intelligently. Given the remarkable merits of simplicity, logic operation, and portable output, the metal ion-driven DNA logic gate of gas pressure provides a promising way for intelligent and portable biosensing.

Selective recognition of Hg2+ ions in aqueous solution by a CdII-based metal-organic framework with good stability and vacant coordination sites

A novel water-stable Cd^II-based metal-organic framework, namely {[Cd(BIBT)(TDC)]·2H₂O}_n (JXUST-28, BIBT = 4,7-bi(1H-imidazol-1-yl)benzo-[2,1,3]thiadiazole and H₂TDC = 2,5-thiophenedicarboxylic acid), was synthesized using a mixed-ligand strategy. Structural analysis demonstrates that JXUST-28 exhibits a two-dimensional layer structure with 4-connected sql topology. Intriguingly, JXUST-28 presents good stability in boiling water (at least 5 days), common organic solvents and aqueous solutions with different pH values of 2-12 (more than 24 hours). Furthermore, fluorescence experiments revealed that JXUST-28 could sense Hg²⁺ ions in aqueous solution via a quenching effect with a detection limit of 0.097 μM. Meanwhile, JXUST-28 can also be regenerated at least 5 times to detect Hg²⁺ ions. In addition, light-emitting diode lamps, luminescent films, and test papers of JXUST-28 have been successfully developed for practical applications.

Colorimetric detection of heavy metal ions with various chromogenic materials: Strategies and applications

Detection of heavy metal ions has drawn significant attention in environmental and food area due to their threats to the human health and ecosystem. Colorimetry is one of the most frequently-used methods for the detection of heavy metal ions owing to its simplicity, easy operation and rapid on-site detection. The development of chromogenic materials and their sensing mechanisms are the key research direction in the area of colorimetric method. Since each chromogenic material has their unique optical and chemical properties, they have totally different colorimetric sensing mechanisms. This review focuses on the chromogenic materials and their sensing strategies for the colorimetric detection of heavy metal ions. We divide the chromogenic materials into three types, including organic materials, inorganic materials, and other materials. As for each type of chromogenic material, we discuss their detailed sensing strategies, sensing performance, and real sample applications. Moreover, current challenges and perspectives related to the colorimetry of heavy metal ions are also discussed in this review. The aim of this review is to help readers to better understand the principles of colorimetric methods for heavy metal ions and push the development of rapid detection of heavy metal ions.

Nanomaterials-Based Electrochemiluminescence Biosensors for Food Analysis: Recent Developments and Future Directions

Developing robust and sensitive food safety detection methods is important for human health. Electrochemiluminescence (ECL) is a powerful analytical technique for complete separation of input source (electricity) and output signal (light), thereby significantly reducing background ECL signal. ECL biosensors have attracted considerable attention owing to their high sensitivity and wide dynamic range in food safety detection. In this review, we introduce the principles of ECL biosensors and common ECL luminophores, as well as the latest applications of ECL biosensors in food analysis. Further, novel nanomaterial assembly strategies have been progressively incorporated into the design of ECL biosensors, and by demonstrating some representative works, we summarize the development status of ECL biosensors in detection of mycotoxins, heavy metal ions, antibiotics, pesticide residues, foodborne pathogens, and other illegal additives. Finally, the current challenges faced by ECL biosensors are outlined and the future directions for advancing ECL research are presented.

Polythionine-mediated AgNWs-AuNPs aggregation conductive network: Fabrication of molecularly imprinted electrochemiluminescence sensors for selective capture of kanamycin

A molecularly imprinted electrochemiluminescence (ECL) sensor was developed for the specific detection of kanamycin in food using silver nanowires-gold nanoparticles (AgNWs-AuNPs) as a luminophore. Polythionine (pThi), another key component of the luminescent layer, can be used as an accelerator of the coreactant and can promote the formation of the AgNWs-AuNPs conductive network. In addition, molecularly imprinted polymers (MIPs) were polymerized on the AgNWs-AuNPs/pThi conductive network, which laid the foundation for the specific capture of kanamycin. The preparation and testing conditions of the sensor were optimized, and the performance was characterized. Under optimal conditions, the ECL intensity of AgNWs-AuNPs/pThi/MIP/GCE showed a good linear relationship (R² = 0.9956) with kanamycin concentration (1 × 10^-10-1 × 10^-6 M) and a low detection limit (3.14 × 10^-11 M, S/N = 3), showing satisfactory selectivity and stability. As proof, AgNWs-AuNPs/pThi/MIP/GCE was successfully used to detect kanamycin in actual samples with satisfactory recovery (83.27-94.13%), which was in good agreement with the results of HPLC-MS/MS (82.26-95.82%). The successful preparation of AgNWs-AuNPs/pThi/MIP/GCE in this experiment provided a new pathway for designing ECL components and constructing an ultrasensitive sensing platform in the field of hazardous substance detection.

Progress and Prospects of Electrochemiluminescence Biosensors Based on Porous Nanomaterials

Porous nanomaterials have attracted much attention in the field of electrochemiluminescence (ECL) analysis research because of their large specific surface area, high porosity, possession of multiple functional groups, and ease of modification. Porous nanomaterials can not only serve as good carriers for loading ECL luminophores to prepare nanomaterials with excellent luminescence properties, but they also have a good electrical conductivity to facilitate charge transfer and substance exchange between electrode surfaces and solutions. In particular, some porous nanomaterials with special functional groups or centered on metals even possess excellent catalytic properties that can enhance the ECL response of the system. ECL composites prepared based on porous nanomaterials have a wide range of applications in the field of ECL biosensors due to their extraordinary ECL response. In this paper, we reviewed recent research advances in various porous nanomaterials commonly used to fabricate ECL biosensors, such as ordered mesoporous silica (OMS), metal–organic frameworks (MOFs), covalent organic frameworks (COFs) and metal–polydopamine frameworks (MPFs). Their applications in the detection of heavy metal ions, small molecules, proteins and nucleic acids are also summarized. The challenges and prospects of constructing ECL biosensors based on porous nanomaterials are further discussed. We hope that this review will provide the reader with a comprehensive understanding of the development of porous nanomaterial-based ECL systems in analytical biosensors and materials science.

A novel sensor for visual and selective detection of Hg2+ based on functionalized doped quantum dots

In this paper, a novel analytical platform for the visual, sensitive and reliable analysis of mercury ions (Hg²⁺) is fabricated based on functionalized doped quantum dots. We synthesized a new specific nano-material, zinc dithiothreitol combined with graphene quantum dots (ZnNCs-NGQDs), by a simple and convenient method which, as an efficient luminophore, was then applied to construct an electrochemiluminescence (ECL) system for the first time. Under optimized conditions, the ECL sensor showed an excellent response for Hg²⁺ in the linear range of 1.0 mM to 10 pM, with a low detection limit of 3 pM. Moreover, the proposed method demonstrated satisfactory selectivity, stability and acceptable reproducibility for the detection of Hg²⁺. The recovery of tap water and lake water samples ranged from 96% to 105%, indicating the potential applicability of the proposed method for monitoring environmental water samples. Meanwhile, visual attempts for mercury ion detection by using doped quantum dots have also obtained satisfactory results. Importantly, our research revealed a viable method for improving the sensitivity and convenience of target studies in sensing fields derived from functional material design.

Copper Ion and Ruthenium Complex Codoped Polydopamine Nanoparticles for Magnetic Resonance/Photoacoustic Tomography Imaging-Guided Photodynamic/Photothermal Dual-Mode Therapy

Phototherapy, such as photodynamic therapy (PDT) and photothermal therapy (PTT), refers to the therapeutic strategy using a visible or near-infrared (NIR) laser to generate free radicals or heat for noninvasive and localized tumor treatment. However, limited by the low photoconversion efficiency of therapeutic agents, a single treatment method can hardly lead to complete tumor ablation, even when enhancing the power density of the laser and/or prolonging the irradiation duration. In this work, copper ion and ruthenium complex codoped polydopamine nanoparticles (Cu(II)/LRu/PDA NPs) are designed for PDT/PTT dual-mode therapy. The doped LRu in the NPs can generate reactive oxygen species under visible laser irradiation and enable PDT. Because of the strong absorption in the NIR region, PDA can not only generate heat for PTT under irradiation but also be used for photoacoustic tomography (PAT) imaging. Meanwhile, the doping of Cu(II) in the NPs through the coordination with PDA facilitates T₁-weighted magnetic resonance imaging (MRI). Thus, MR/PAT imaging-guided PDT/PTT dual-mode therapy is achieved. The in vivo experiments indicate that the Cu(II)/LRu/PDA NPs can accumulate in HeLa tumors with a retention rate up to 8.34%ID/g. MR/PAT imaging can clearly identify the location and boundary of the tumors, permitting precise guidance for phototherapy. Under the combined effect of PDT and PTT, a complete ablation of HeLa tumors is achieved. The current work provides an alternative nanoplatform for performing PDT/PTT dual-mode therapy, which can be further guided by MR/PAT imaging.

A novel water-soluble naphthalimide-based turn-on fluorescent probe for mercury ion detection in living cells and zebrafish

Mercury (Hg), as the only heavy metal that can complete the cycle in the biosphere, can further accumulate in the human body through the food chain, causing irreversible damage to...

Conjugated Polymers for Biomedical Applications

Conjugated polymers (CPs) are a series of organic semiconductor materials with large π-conjugated backbones and delocalized electronic structures. Due to their specific photophysical properties and photoelectric effects, plenty of CPs...

Biothiol-Functionalized Cuprous Oxide Sensor for Dual-Mode Sensitive Hg2+ Detection

Hg²⁺ ions are one of the highly poisonous heavy metal ions in the environment, so it is urgent to develop rapid and sensitive detection platforms for detecting Hg²⁺ ions. In this work, a novel electrochemical and photoelectrochemical dual-mode sensor (l-Cys-Cu₂O) was successfully fabricated, and the sensor exhibits a satisfactory detection limit (0.2 and 0.01 nM) for the detection of Hg²⁺, which is far below the dangerous limit of the U.S. Environmental Protection Agency. The linear ranges of dual-mode Hg²⁺ detections were 0.33-3.3 and 0.17-1.33 μM, respectively. Moreover, the sensor shows desirable stability, selectivity, and reproducibility for detecting Hg²⁺ ions. For river water samples, the recoveries of 96.6-101.4% (electrochemical data) and 93.0-105.6% (photoelectrochemical data) were obtained, indicating that the sensor could be successfully applied in the determination of Hg²⁺ ions in environmental water. Therefore, the designed sensor has a potential in the trace-level detection of Hg²⁺ ions.