Magnetic assisted fluorescence immunoassay for sensitive chloramphenicol detection using carbon dots@CaCO3 nanocomposites

Molecular imprinting electrochemical sensor based on hollow spherical PProDOT-2CH2OH and chitosan-derived carbon materials for highly sensitive detection of chloramphenicol

The misuse of chloramphenicol (CAP) has jeopardized environmental safety. It is critical to create an effective and sensitive CAP detection technique. In this paper, a composite of chitosan (CS)-derived carbon material modified hollow spherical hydroxylated poly(3,4-propylenedioxythiophene) (PProDOT-2CH2OH) was designed, which innovatively used o-phenylenediamine and p-aminobenzoic acid as bi-functional monomers to prepare molecular imprinting polymer (MIP) sensors for highly sensitive analysis and determination of CAP. It was found that the hollow spherical structure of PProDOT-2CH2OH significantly enhanced the rapid electron migration. When combined with the CS-derived carbon material, which has multi-functional sites, it improved the electrical activity and stability of the sensor. It also provided more active centers for the MIP layer to specifically recognize CAP. Therefore, this MIP sensor had a wide linear response (0.0001 ∼ 125 μM), a low limit of detection (LOD, 6.6 pM), excellent selectivity and stability. In addition, studies showed that the sensor has potential practical value. ENVIRONMENTAL IMPLICATION: Chloramphenicol (CAP) is one of the most widely used antibiotics with the highest dosage due to its low price and broad-spectrum antimicrobial properties. Due to its incomplete metabolism in living organisms and its difficulty in degrading in the environment, contamination caused by it can pose a threat to public health. In this study, a novel molecularly imprinted sensor (MIP/PC2C1/GCE) was designed to provide a new idea for rapid and precise removal of CAP by adsorption. The detection of CAP in pharmaceutical, water quality, and food fields was realized.

Exploring the potential of eco-friendly carbon dots in monitoring and remediation of environmental pollutants

Photoluminescent carbon dots (CDs) have garnered significant interest owing to their distinctive optical and electronic properties. In contrast to semiconductor quantum dots, which incorporated toxic elements in their composition, CDs have emerged as a promising alternative, rendering them suitable for both environmental and biological applications. CDs exhibit astonishing features, including photoluminescence, charge transfer, quantum confinement effect, and biocompatibility. Recently, CDs derived from green sources have drawn a lot of attention due to their strong photostability, reduced toxicity, better biocompatibility, enhanced fluorescence, and simplicity. These attributes have shown great promise in the areas of LED technology, bioimaging, photocatalysis, drug delivery, biosensing, and antibacterial activity. In contrast, this review offers a comprehensive overview of various green sources utilized to produce CDs and methodologies, along with their merits and demerits, with a notable emphasis on physiochemical properties. Additionally, the paper provides insight into the bibliometric analysis and recent advancements of CDs in sensing, photocatalysis, and antibacterial activity. In this field, extensive research is underway, and a total of 7,438 articles have been identified. Among these, 4242 articles are dedicated to sensing applications, while 1518 and 1678 focus on adsorption and degradation. Carbon dots demonstrate exceptional sensing capabilities within the nanomolar range with a selectivity of up to 95% for pollutants. They exhibit excellent degradation efficiency exceeding 90% within 10-130 min and possess an adsorption capacity from 100 to 800 mg/g. These fascinating qualities render them suitable for diverse applications.

Ultrasensitive Ti3C2Tx@Pt-Based Immunochromatography with Catalytic Amplification and a Dual Signal for the Detection of Chloramphenicol in Animal-Derived Foods

Herein, a catalytic amplification enhanced dual-signal immunochromatographic assay (ICA) based on Pt nanoparticles (Pt NPs) modified with Ti3C2Tx MXene (Ti3C2Tx@Pt) was first developed for chloramphenicol (CAP) in animal-derived foods. Due to the large specific surface area and abundant active sites of Ti3C2Tx@Pt, they can be loaded with hundreds of Pt NPs to enhance their catalytic activity, resulting in a significant increase in the detection sensitivity; the sensitivity was up to 50-fold more sensitive than the reported ICA for CAP. The LODs of the developed method for milk/chicken/fish were 0.01 μg/kg, the LOQs were 0.03 μg/kg and the recovery rates were 80.5-117.0%, 87.2-118.1% and 92.7-117.9%, with corresponding variations ranging from 3.1 to 9.6%, 6.0 to 12.7% and 6.0 to 13.6%, respectively. The linear range was 0.0125-1.0 μg/kg. The results of the LC-MS/MS confirmation test on 30 real samples had a good correlation with that of our established method (R2 > 0.98), indicating the practical reliability of the established method. The above results indicated that an ICA based on the Ti3C2Tx@Pt nanozyme has excellent potential as a food safety detection tool.

Immunoassays: Analytical and Clinical Performance, Challenges, and Perspectives of SERS Detection in Comparison with Fluorescent Spectroscopic Detection

Immunoassays (IAs) with fluorescence-based detection are already well-established commercialized biosensing methods, such as enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay (LFIA). Immunoassays with surface-enhanced Raman spectroscopy (SERS) detection have received significant attention from the research community for at least two decades, but so far they still lack a wide clinical commercial application. This review, unlike any other review that we have seen, performs a three-dimensional performance comparison of SERS IAs vs. fluorescence IAs. First, we compared the limit of detection (LOD) as a key performance parameter for 30 fluorescence and 30 SERS-based immunoassays reported in the literature. We also compared the clinical performances of a smaller number of available reports for SERS vs. fluorescence immunoassays (FIAs). We found that the median and geometric average LODs are about 1.5-2 orders of magnitude lower for SERS-based immunoassays in comparison to fluorescence-based immunoassays. For instance, the median LOD for SERS IA is 4.3 × 10-13 M, whereas for FIA, it is 1.5 × 10-11 M. However, there is no significant difference in average relative standard deviation (RSD)-both are about 5-6%. The analysis of sensitivity, selectivity, and accuracy reported for a limited number of the published clinical studies with SERS IA and FIA demonstrates an advantage of SERS IA over FIA, at least in terms of the median value for all three of those parameters. We discussed common and specific challenges to the performances of both SERS IA and FIA, while proposing some solutions to mitigate those challenges for both techniques. These challenges include non-specific protein binding, non-specific interactions in the immunoassays, sometimes insufficient reproducibility, relatively long assay times, photobleaching, etc. Overall, this review may be useful for a large number of researchers who would like to use immunoassays, but particularly for those who would like to make improvements and move forward in both SERS-based IAs and fluorescence-based IAs.

Dual-layers Raman reporter-tagged Au@Ag combined with core-satellite assemblies for SERS detection of Zearalenone

Zearalenone (ZEN) is a prevalent mycotoxin identified in corn. A SERS-based immunosensor by constructing core-satellite assemblies was developed for ZEN detection. ZEN monoclonal antibody modified gold nanostars (AuNSs) were fabricated as the capture probe (core). The Raman signal probes (satellites) utilized ZEN antigen linked to the core-shell structures loaded with two layers of Raman reporter molecules (AuMBA@AgMBANPs). The coupling between AuNSs and AuMBA@AgMBANPs can produce a poweful electromagnetic field, thus considerably amplifying the Raman signal. The detection range of ZEN for corn samples under the optimal conditions was 5 ∼ 400 μg/kg with a LOD of 3 μg/kg, which completely satisfying the requirement of maximum residual level (60 μg/kg). Moreover, the proposed SERS method was consistent with the HPLC-FLD method for the detection of ZEN in naturally contaminated corn samples (90.58% ∼ 105.29%). Conclusively, fabricated immunosensor with exceptional sensitivity and specificity broaden the application of SERS in mycotoxin detection.

Lateral Flow Immunoassay Based on Quantum-Dot Nanobeads for Detection of Chloramphenicol in Aquatic Products

Quantum dot nanobeads (QBs) were used as signal source to develop competitive lateral flow immunoassay (LFIA) for the detection of chloramphenicol (CAP). The quantitative detection of CAP was achieved by calculating the total color difference (∆E) values of the test line (T line) using the images of test strips. QB-based LFIA (QBs-LFIA) allowed the effective dynamic linear detection of CAP in the range of 0.1-1.5 ng/mL. The limit of detection (LOD) was 3.0 ng/mL, which was 50 and 667 times lower than those achieved for two different brands of colloidal gold kits. The recoveries of CAP during real-sample detection were 82.82-104.91% at spiked levels of 0.1, 0.7, and 1.5 ng/mL. These results indicate that the developed QBs-LFIA facilitates the sensitive detection of CAP.

Fabrication of Biomimetic Cascade Nanoreactor Based on Covalent Organic Framework Capsule for Biosensing

The cooperation of biocatalysis and chemocatalysis in a catalytic cascade reaction has received extensive attention in recent years, whereas its practical applications are still hampered due to the fragility of the enzymes, poor compatibility between the carriers and enzymes, and limited catalytic efficiency. Herein, a biomimetic cascade nanoreactor (GOx@COFs@Os) was presented by integrating glucose oxidase (GOx) and Os nanozyme with covalent organic framework (COF) capsule using metal-organic framework (ZIF-90) as a template. The obtained GOx@COFs@Os capsule provided a capacious microenvironment to retain the conformational freedom of GOx for maintaining its activity, wherein the enzyme activity of GOx in COF capsules was equal to 92.9% of the free enzyme and was 1.88-folds higher than that encapsulated in ZIF-90. Meanwhile, the COF capsule could protect the GOx against incompatible environments (high temperature, acid, and organic solvents), resulting in improved stability of the packaged enzymes. Moreover, the COF capsule with great pore structure significantly improved the affinity to substrates and facilitated efficient mass transfer, which achieved 2.19-folds improvement in catalytic efficiency than the free cascade system, displaying the great catalytic performance in the cascade reaction. More importantly, the biomimetic cascade capsule was successfully employed for glucose monitoring, glutathione sensing, and bisphenol S detection in the immunoassay as a proof-of-concept. Our strategy provided a new avenue in the improvement of biocatalytic cascade performance to encourage its wide applications in various fields.

Nanomaterial-based fluorescent biosensors for the detection of antibiotics in foodstuffs: A review

Antibiotics are widely used as bacteriostatic or bactericidal agents against various microbial infections in humans and animals. The excessive use of antibiotics has led to an accumulation of their residues in food products, which ultimately poses a threat to human health. In light of the shortcomings of conventional methods for antibiotic detection (primarily cost, proficiency, and time-consuming procedures), the development of robust, accurate, on-site, and sensitive technologies for antibiotic detection in foodstuffs is important. Nanomaterials with amazing optical properties are promising materials for developing the next generation of fluorescent sensors. In this article, advances in detecting antibiotics in food products are discussed with respect to their sensing applications, with a focus on fluorescent nanomaterials such as metallic nanoparticles, upconversion nanoparticles, quantum dots, carbon-based nanomaterials, and metal-organic frameworks. Furthermore, their performance is evaluated to promote the continuation of technical advances.

Bifunctional magnetic ZnCdSe/ZnS quantum dots nanocomposite-based lateral flow immunoassay for ultrasensitive detection of streptomycin and dihydrostreptomycin in milk, muscle, liver, kidney, and honey

In this study, bifunctional magnetic ZnCdSe/ZnS quantum dots nanocomposite (MQNs) were synthesized, and firstly used to develop a lateral flow immunoassay (LFIA) for streptomycin (STR) and dihydrostreptomycin (DHSTR) detection in milk, muscle, liver, kidney, and honey simultaneously. The fluorescence signal of MQNs was 9-fold stronger than that of the original quantum dots. The detection limits of the established MQNs-LFIA for STR and DHSTR in five samples were 0.08-1.78 μg/kg, the quantitation limits were 0.26-5.87 μg/kg, the recoveries were between 85.0% and 120.0%, and the coefficient of variations were between 0.8% and 19.3%, respectively. The sensitivity was up to 42-fold more sensitive than the reported LFIAs. The single blind test results of 25 samples were consistent with that of the confirmation method (R² ≥ 0.99). Besides, a portable reader was self-developed and used for rapid quantification. Our study demonstrated MQNs as a promising signal-amplifying tag can be used for ultrasensitive detection of chemical contaminants in foods.

Introduction of multilayered magnetic core-dual shell SERS tags into lateral flow immunoassay: A highly stable and sensitive method for the simultaneous detection of multiple veterinary drugs in complex samples

Direct, convenient, and sensitive monitoring of the residues of multiple drugs in complex environments is important but remains a challenge. Here, we report a surface-enhanced Raman scattering (SERS)-based multiplexed lateral flow immunoassay (LFA) that supports the simultaneous and sensitive detection of commonly used drugs kanamycin, ractopamine, clenbuterol, and chloramphenicol in unprocessed complex samples through the dual signal amplification strategy of numerous efficient hotspots and magnetic enrichment. Multilayered magnetic-core dual-shell nanoparticles (MDAu@Ag) with controllable subtle nanogaps were fabricated via the polyethyleneimine-mediated layer-by-layer (LBL) assembly of two layers of Au@Ag satellites onto superparamagnetic Fe₃O₄ cores and conjugated with specific antibodies as multifunctional tags in the LFA system for rapid capture, separation, and quantitative analysis. Two Raman reporters were embedded in internal nanogaps and modified on the surface of MDAu@Ag for the simultaneous and ultrasensitive detection of four targets on two test lines, which greatly simplified the fabrication and signal reading of SERS-LFA. The proposed assay can rapidly detect multiple drug residues in 35 min with detection limits down to pg/mL level. Moreover, the MDAu@Ag-based SERS-LFA demonstrated better stability, higher throughput, and superior sensitivity (at least 400 times) than traditional colloidal gold immunochromatography, showing its great potential in the field of point-of-care testing.

Stimuli-responsive SERS biosensor for ultrasensitive tetracycline sensing using EDTA-driven PEI@CaCO3 microcapsule and CS@FeMMs

In this work, a stimuli-responsive SERS biosensor was fabricated for tetracycline (TTC) by "signal-on" strategy using (EDTA)-driven polyethyleneimine grafted calcium carbonate (PEI@CaCO₃) microcapsule and chitosan-Fe magnetic microbeads (CS@FeMMs). Initially, aptamer conjugated magnetic-bead CS@FeMMs@Apt with superparamagnetism and excellent biocompatibility was employed as capture probe, which facilitated the rapid and easy magnetic separation. Subsequently, the PEI cross-linked layer and aptamer network layer were constructed onto the outer layer of CaCO₃@4-ATP microcapsule to form sensing probes (PEI@CaCO₃@4-ATP@Apt) via the layer-by-layer assembly method. In the presence of TTC, a sandwich SERS-assay was exploited by aptamer recognition induced target-bridged strategy. When the solution of EDTA was added, the core layer of CaCO₃ would be dissolved quickly, destroying the microcapsule to release 4-ATP. The released 4-ATP could be quantitatively monitored by dripping the supernatant onto the AuNTs@PDMS SERS platform, resulting in a strong Raman "signal-on". Under the optimal conditions, a good linear relationship was established with a correlation coefficient (R²) of 0.9938 and a LOD of 0.03 ng/mL. Additionally, the application capacity of the biosensor to detect TTC was also affirmed in food matrixes, and the results were consistent with the standard ELISA method (P > 0.05). Hence, this SERS biosensor affords extensive application prospects for TTC detection with multiple merits such as high sensitivity, environment friendliness, and high stability.

How Exactly Do AIEgens Target Bacteria? Leveraging the Targeting Mechanism to Design Sensitive Fluorescent Immunosensors

Aggregation-induced emission luminogens (AIEgens) are promising candidates for bacterial imaging and detection because they can "Light-Up" pathogenic bacteria without complicated labeling or washing steps. However, there have been few in-depth analyses of the intrinsic mechanism underlying their utility as fluorescence probes for targeting bacteria. Therefore, using large-scale molecular dynamics simulations, we investigated the mechanism of their bacterial "Light-Up" behavior with N,N-diphenyl-4-(7-(pyridin-4-yl)benzo[c][1,2,5]thiadiazol-4-yl) aniline functionalized with 1-bromoethane (TBP-1). We propose that the triphenylamine motif of TBP-1, rather than the positively charged pyridine group, first contacts the cell membrane. After TBP-1 completely inserts into the cell membrane, the hydrophobic triphenylamine motif localizes in the hydrophobic core of the cell membrane, restricting the molecular variation of TBP-1, which induces the fluorescent "turn-on" and bacterial "Light-Up." On this basis, we established a heterogeneous lateral flow immunoassay (LFIA) for the detection of foodborne pathogens. The LFIA system showed improved sensitivity with a limit of detection as low as 10³ CFU mL^-1 and strong specificity. Our protocol opened an effective shortcut to the design of more efficient AIEgens and novel AIEgens-based immunoassays.

AIEgens: Next Generation Signaling Source for Immunoassays?

Luminogens with aggregation-induced emission (AIEgens) properties have numerous broad applications in fields of chemical and biological analyses due to their exceptional photostability, excellent signal reliability, high quantum yield, and large Stokes' shift. In particular, AIEgens also bring new blood for immunoassay. Since publication of the first 2004 paper, AIEgens-based immunoassays have received significant attention because of their high sensitivity, specificity, accuracy, and reliability. However, until now, there have been no comprehensive literature reviews focused on the evolving field of AIEgens-based immunoassays. Thus, we have extensively reviewed AIEgens-based immunoassays from their basic working principles to specific applications. We focus on several fundamental elements of AIEgens-based immunoassays, including the typical structures of AIEgens, emission mechanism of AIEgens probes, function of AIEgens in immunoassays, and platform of AIEgens-based immunoassays. Then, the representative applications of AIEgens-based immunoassays in food safety, medical diagnostics, and environmental monitoring are explored. Thus, proposals on how to further improve the AIEgens-based immunoassay performance are also discussed, as well as future challenges and perspectives, aiming to provide brief and valid guidelines for choosing suitable AIEgens-based immunoassays according to specific application requirements.

Synergistic Effect of Oxygen- and Nitrogen-Containing Groups in Graphene Quantum Dots: Red Emitted Dual-Mode Magnetic Resonance Imaging Contrast Agents with High Relaxivity

Contrast agents (CAs) in magnetic resonance imaging generally involve the dissociative Gd³⁺. Because of the limited ligancy of Gd³⁺, the balance between Gd³⁺ coordination stability (reducing the concentration of dissociative Gd³⁺) and increases in the number of coordination water molecules (enhancing the relaxivity) becomes crucial. Herein, the key factor of the synergistic effect between the O- and N-containing groups of graphene quantum dots for the structural design of CAs with both high relaxivity and low toxicity was obtained. The nitrogen-doped graphene quantum dots (NGQDs) with an O/N ratio of 0.4 were selected to construct high-relaxivity magnetic resonance imaging (MRI)-fluorescence dual-mode CAs. The coordination stability of Gd³⁺ can be increased through the synergetic coordination of O- and N-containing groups. The synergetic coordination of O- and N-containing groups can result in the short residency time of the water ligand and achieve high relaxivity. The resulting CAs (called NGQDs-Gd) exhibit a high relaxivity of 32.04 mM^-1 s^-1 at 114 μT. Meanwhile, the NGQDs-Gd also emit red fluorescence (614 nm), which can enable the MRI-fluorescence dual-mode imaging as the CAs. Moreover, the bio-toxicity and tumor-targeting behavior of NGQDs-Gd were also evaluated, and NGQDs-Gd show potential in MRI-fluorescence imaging in vivo.

A review on recent advances in the applications of composite Fe3O4 magnetic nanoparticles in the food industry

Fe3O4 magnetic nanoparticles (MNPs) have attracted tremendous attention due to their superparamagnetic properties, large specific surface area, high biocompatibility, non-toxicity, large-scale production, and recyclability. More importantly, numerous hydroxyl groups (-OH) on the surface of Fe3O4 MNPs can provide coupling sites for various modifiers, forming versatile nanocomposites for applications in the energy, biomedicine, and environmental fields. With the development of science and technology, the potential of nanotechnology in the food industry has also gradually become prominent. However, the application of composite Fe3O4 MNPs in the food industry has not been systematically summarized. Herein, this article reviews composite Fe3O4 MNPs, including their properties, modifications, and physical functions, as well as their applications in the entire food industry from production to processing, storage, and detection. This review lays a solid foundation for promoting food innovation and improving food quality and safety.

A rare monoclonal antibody discovery based on indirect competitive screening of a single hapten-specific rabbit antibody secreting cell

A rare antibody that is able to tolerate physio-chemical factors is preferred and highly demanded in diagnosis and therapy. Rabbit monoclonal antibodies (RmAbs) are distinguished owing to their high affinity and stability. However, the efficiency and availability of traditional methods for RmAb discovery are limited, particularly for small molecules. Here, we present an indirect competitive screening method in nanowells, named CSMN, for single rabbit antibody-secreting cells (ASCs) selection with 20.6 h and propose an efficient platform for RmAb production against small molecules within 5.8 days for the first time. Chloramphenicol (CAP) as an antibacterial agent poses a great threat to public health. We applied CSMN to select CAP-specific ASCs and produced one high-affinity RmAb, surprisingly showed extremely halophilic properties with an IC₅₀ of 0.08 ng mL^-1 in the saturated salt solution, which has not yet been seen for other antibodies. The molecular dynamic simulation showed that the negatively charged surface improved the stability of the RmAb structure with additional disulfide bonds compared with mouse antibodies. Moreover, the reduced solvent accessible surface area of the binding pocket increased the interactions of RmAb with CAP in a saturated salt solution. Furthermore, RmAb was used to develop an immunoassay for the detection of CAP in real biological samples with simple pretreatment, shorter assay time, and higher sensitivity. The results demonstrated that the practical and efficient CSMN is suitable for rare RmAb discovery against small molecules.

Immunosensor of Nitrofuran Antibiotics and Their Metabolites in Animal-Derived Foods: A Review

Nitrofuran antibiotics have been widely used in the prevention and treatment of animal diseases due to the bactericidal effect. However, the residual and accumulation of their metabolites in vivo can pose serious health hazards to both humans and animals. Although their usage in feeding and process of food-derived animals have been banned in many countries, their metabolic residues are still frequently detected in materials and products of animal-derived food. Many sensitive and effective detection methods have been developed to deal with the problem. In this work, we summarized various immunological methods for the detection of four nitrofuran metabolites based on different types of detection principles and signal molecules. Furthermore, the development trend of detection technology in animal-derived food is prospected.

Plasma colorimetric aptasensor for the detection of chloramphenicol in honey based on cage Au@AuNPs and cascade hybridization chain reaction

A plasma colorimetric aptasensor was developed for rapid determination of chloramphenicol (CAP) in honey on site. Herein, cage gold shell@core nanoparticles (Au@AuNPs) were synthesized to enhance signal response and broaden the linear range. In addition, aptamer-based cascade hybridization chain reaction (cHCR), consisting of HP1, HP2, HP3, and HP4, was also designed for signal amplification and specific analysis. In this assay, HP1 and HP4 were immobilized on the surface of cage Au@AuNPs. In the presence of CAP, cHCR was triggered, and frond-like DNA products were formed, which made the distance among the cage Au@AuNPs closer and the system color changed from red to deep purple. Qualitative and quantitative analysis were carried out according to color changes and UV-Vis spectra. Under the optimized conditions, the wavelength of UV-Vis absorption peak exhibited a good linear relationship with CAP concentration in the range of 5.0 to 500 nmol/L with the detection limit of 1.2 nmol/L (S/N = 3). This aptasensor also showed good specificity for CAP detection compared with other antibiotics similar to the target analyte. Furthermore, the colorimetric aptasensor was successfully applied to the detection of CAP in honey with recoveries of 88.0-107.6%. This cHCR-based aptasensing for CAP possesses high sensitivity, good selectivity, low cost and excellent stability, and could be extended to detect a wide variety of other small molecular analytes, nucleic acids or proteins. Therefore, the versatile method might become a potential alternative tool in food analysis and environmental monitoring.

Development of a Highly Sensitive and Specific ic-ELISA and Lateral Flow Immunoassay for Diacetoxyscirpenol

To monitor the contamination of a type A trichothecene, diacetoxyscirpenol (DAS), one monoclonal antibody (mAb) 8A9 with high affinity and specificity was prepared in the present study. The mAb 8A9 showed a 50% inhibition concentration (IC₅₀) of 0.31 μg/L, which is of the highest affinity reported to date. An indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and lateral flow immunoassay (LFIA) based on mAb 8A9 were developed and exhibited limits of detection as low as 0.65 μg/kg and 100 μg/kg in rice samples, respectively. The molecular recognition mechanism of mAb 8A9 to DAS was explored by molecular docking. The results showed that the hydrophobic amino acids of mAb 8A9 interacted with DAS by forming hydrogen bonds and a pi-sigma bond, which lead to a highly specific recognition of DAS. In summary, we produced one mAb, developed ELISA and LFIA for DAS detection in rice with significantly sensitivity, specificity, accuracy, and precision.

Formation of calcium carbonate nanoparticles through the assembling effect of glucose and the influence on the properties of PDMS

In order to prepare calcium carbonate nanoparticles in a green and environmentally friendly way, the concept of bio-mineralization has been proposed. Glucose, as a common small molecular organic substance found in organisms, participates in the mineralization process in cells. By adding glucose as a chemical additive, long chains of calcium carbonate form at the initial stage and then break granularly via over-carbonation. The average size of the calcium carbonate nanoparticles is about 40 nm based on the statistical analyses of three hundred particles. The growth mechanism of calcium carbonate under the influence of glucose is obtained. After the calcium carbonate nanoparticles are modified by sodium stearate, they are introduced to the PDMS matrix to achieve the composite material. Compared with pure PDMS, the composite with additional 3% calcium carbonate has its elongation at break and tensile strength increased by 23.96% and 48.15%, respectively.

In order to prepare calcium carbonate nanoparticles in a green and environmentally friendly way, the concept of bio-mineralization has been proposed.

Chloramphenicol-activated electro-chemiluminescent behavior of BNQDs-Ru(phen)32+ system for ultra-sensitive sensing of chloramphenicol in pharmaceutical and milk samples

To improve the sensitivity for electro-chemiluminescent (ECL) detection of chloramphenicol (CAP), a common broad-spectrum antibiotic, boron nitride quantum dots (BNQDs) were prepared with excellent photoelectric property and low toxicity. After its structure and electrochemical property were investigated in detail, it was noted that the ECL signal of Ru(Phen)₃²⁺could be strengthened by the proposed BNQDs, which was further activated by ten's times in the presence of CAP. Under the optimized conditions, there was an excellent linear relationship between ΔECL and lgc_CAPin a wide linear range from 1.0 × 10^-10to 1.0 × 10^-6mol l^-1CAP. The detection limit was super-low to be 3.3 × 10^-11mol l^-1(S/N = 3). When applied for CAP detection in real pharmaceutical and food samples, the recoveries were between 97.8% and 105.7% with R.S.D. less than 3.3%. A possible CAP-activated ECL mechanism of BNQDs-Ru(phen)₃²⁺was also proposed. This work will offer a great potential for efficient monitoring of CAP pollution and clinical diagnosing of CAP-related diseases in future.

Recyclable Magnetic Fluorescence Sensor Based on Fe3O4 and Carbon Dots for Detection and Purification of Methcathinone in Sewage

Sensitive, rapid, and low-cost detection of drug traces in sewage is very important for drug monitoring and control. In this study, a dual functional and recyclable magnetic fluorescent molecularly imprinted polymers (MFMIPs) sensor with high sensitivity for rapid detection and purification of methcathinone in sewage was developed. MFMIPs was prepared via molecular imprinting and conjugation with carbon dots as a fluorescent reporter on Fe₃O₄ (Fe₃O₄-MIPs@CDs). With strong recognition and adsorption toward methcathinone by the specific cavities on the surface of MFMIPs, the fluorescence of the sensor could dramatically be quenched once anchored with methcathinone. Under optimal conditions, the MFMIPs sensor presented high sensitivity with a linear range of 0.5-100 nM and a detection limit of 0.2 nM, which would be used to monitor drug prevalence and consumption within a certain region. This sensor was applied to the assay of methcathinone in sewage samples collected from Yuebeiyuan, Yanghu, and Xujiahu sewage pumping stations of Yuelu District. The calculated concentrations of methcathinone were 4.80, 15.33, and 8.59 nM in sewage samples, which were in good agreement with data tested by LC-MS/MS. For another function, MFMIPs exhibited purification toward methcathinone and the adsorption capacity was about 0.27 mg/g in a real sewage sample. Moreover, the sensor could be recycled and reused at least five times with the aid of an external magnetic field. Collectively, with good analytical performance and excellent recognition and selectivity to methcathinone, the proposed sensing system based on the magnetic core and molecularly imprinted polymers would open a door to establish highly sensitive and effective sensing systems for sewage analysis and purification.

Molecularly Imprinted Silica-Coated CdTe Quantum Dots for Fluorometric Determination of Trace Chloramphenicol

A dual recognition system with a fluorescence quenching of quantum dots (QDs) and specific recognition of molecularly imprinted polymer (MIP) for the detection of chloramphenicol (CAP) was constructed. MIP@SiO₂@QDs was prepared by reverse microemulsion method with 3-aminopropyltriethoxysilane (APTS), tetraethyl orthosilicate (TEOS) and QDs being used as the functional monomer, cross-linker and signal sources, respectively. MIP can specifically recognize CAP, and the fluorescence of QDs can be quenched by CAP due to the photo-induced electron transfer reaction between CAP and QDs. Thus, a method for the trace detection of CAP based on MIP@SiO₂@QDs fluorescence quenching was established. The fluorescence quenching efficiency of MIP@SiO₂@QDs displayed a desirable linear response to the concentration of CAP in the range of 1.00~4.00 × 10² μmol × L⁻¹, and the limit of detection was 0.35 μmol × L⁻¹ (3σ, n = 9). Importantly, MIP@SiO₂@QDs presented good detection selectivity owing to specific recognition for CAP, and was successfully applied to quantify CAP in lake water with the recovery ranging 102.0~104.0%, suggesting this method has the promising potential for the on-site detection of CAP in environmental waters.

Electrochemical strategies for the detection of cTnI

Acute myocardial infarction (AMI) is the main cause of death from cardiovascular diseases. Thus, early diagnosis of AMI is essential for the treatment of irreversible damage from myocardial infarction. Traditional electrocardiograms (ECG) cannot meet the specific detection of AMI. Cardiac troponin I (cTnI) is the main biomarker for the diagnosis of myocardial infarction, and the detection of cTnI content has become particularly important. In this review, we introduced and compared the advantages and disadvantages of various cTnI detection methods. We focused on the analysis and comparison of the main indicators and limitations of various cTnI biosensors, including the detection range, detection limit, specificity, repeatability, and stability. In particular, we pay more attention to the application and development of electrochemical biosensors in the diagnosis of cardiovascular diseases based on different biological components. The application of electrochemical microfluidic chips for cTnI was also briefly introduced in this review. Finally, this review also briefly discusses the unresolved challenges of electrochemical detection and the expectations for improvement in the detection of cTnI biosensing in the future.