Portable Smartphone-Based QDs for the Visual Onsite Monitoring of Fluoroquinolone Antibiotics in Actual Food and Environmental Samples

A cucurbit[6]uril-based fluorescence supramolecular assembly for information encryption and visualization detection of nitro compounds and antibiotics

A novel CB[6]-based supramolecular assembly [K(ANS)(CB[6])2(DMF)2(H2O)0.5] (1) (CB[6] = cucurbit[6]uril, ANS- = 8-amino-1-naphthalene sulfonic acid ion) was successfully synthesized under solvothermal condition. Performance studies have shown that 1 exhibited excellent chemical stability and recycling performance. Meanwhile, 1 exhibited remarkable potential as a fluorescence sensor for the detection of 2,4,6-trinitrophenol (TNP), 4-nitrophenol (4-NP), and rifampicin (RFP) in both aqueous environments and practical samples. This sensing capability is achieved through fluorescence quenching, which offers fast response times and exceptional sensitivity, with detection limits of 0.19 μM for both TNP and 4-NP, and 0.21 μM for RFP. Even more remarkably, an anti-counterfeiting ink based on 1 and a portable test hydrogel were devised for encrypting information and visually detecting using a smartphone application. This work has the potential to expand the utilization of CB[6]-based materials in optical applications.

Computational simulation-assisted template selection of magnetic MOFs molecularly imprinted materials applying the adsorption and detection of multiple fluoroquinolones

This study utilized computational simulation and surface molecular imprinting technology to develop a magnetic metal-organic framework molecularly imprinted polymer (Fe3O4@ZIF-8@SMIP) capable of selectively recognizing and detecting multiple fluoroquinolones (FQs). The Fe3O4@ZIF-8@SMIP material was synthesized using the "common" template-ofloxacin, identified by computational simulation, demonstrating notable adsorption capacity (88.61-212.93 mg g-1) and rapid mass-transfer features (equilibration time: 2-3 min) for all tested FQs, consistent with Langmuir adsorption model. Subsequently, this material was employed as a magnetic solid-phase-extraction adsorbent for adsorption and detection of multiple FQs by combining with high performance liquid chromatography. The developed method exhibited good linearity for various FQs within the concentration range of 0.1-500 μg L-1, with low limit of detection (0.0605-0.1529 μg L-1) and limit of quantitation (0.2017-0.5097 μg L-1). Satisfactory recoveries (88.38-103.44%) were obtained when applied to spiked food samples, demonstrating the substantial potential of this Fe3O4@ZIF-8@SMIP material for rapid enrichment and identification for multiple FQs residues.

A covalent-organic framework-based platform for simultaneous smartphone detection and degradation of aflatoxin B1

This study developed a smartphone-based biosensor that could simultaneously detect and degrade aflatoxin B1 (AFB1). A donor-acceptor covalent organic framework (COF) was bound onto the surface of stainless-steel mesh (SSM) via the in-situ synthesis, which was used to immobilize the aptamer (Apt) to specifically capture AFB1 and was also as a photocatalyst to degrade AFB1. Au@Ir nanospheres were synthesized, which exhibited better peroxidase catalytic activity (Km=5.36 × 10-6 M, Vmax=3.48 × 10-7 Ms-1, Kcat=1.00 × 107 s-1) than Ir@Au nanospheres, so Au@Ir nanospheres were linked with Apt2 to be utilized as the signal probe. The density functional theory calculation also described that Au@Ir nanospheres possessed the lower energy barriers to decompose H2O2 than Ir@Au nanospheres. Coupled with the "Color Picker" application in the smartphone, the established "sandwich-structure" colorimetric method exhibited a linear range of 0.5-200 μg L-1 and a detection limit of 0.045 μg L-1. The photocatalytic capacity of SSM/COF towards AFB1 was investigated and the degradation rate researched 81.14 % within 120 min under the xenon lamp irradiation, and the degradation products were validated by ESI-MS. It was applied for the detection of AFB1 in peanuts, corn, and wheat samples. Recoveries were ranging from 77.90 % to 112.5 %, and the matrix effect was 75.10-111.6 %. Therefore, the smartphone-based biosensor provided a simple, fast, and sensitive platform for the detection of AFB1, and meanwhile could realize the efficient degradation of AFB1.

A handheld fluorescent lateral flow immunoassay platform for highly sensitive point-of-care detection of methamphetamine and tramadol

The escalating issue of drug abuse poses a significant threat to public health and societal stability worldwide. An on-site drug detection platform is vital for combating drug abuse and trafficking, as it eliminates the need for additional tools, extensive processes, or specialized training. Therefore, it is imperative to develop a fast, sensitive, non-invasive, and reliable multiplex drug testing platform. In this study, we have presented a silica core@dual quantum dot-shell nanocomposite (SI/DQD)-based fluorescent lateral flow immunoassay (LFIA) platform for the highly sensitive and simultaneous point-of-care (POC) detection of methamphetamine (MET) and tramadol (TR). A 3D-printed attachment was designed to integrate optical and electrical components, facilitating the miniaturization of the instrument and reducing both cost and complexity. The device's advanced hardware and effective fluorescence extraction algorithm with waveform reconstruction enable swift, automatic noise reduction and data analysis. SI/DQD nanocomposites were utilized as fluorescent nanotags in the LFIA strips due to their outstanding luminous efficiency and robustness. This LFIA platform achieves impressive detection limits (LODs) of 0.11 ng mL-1 for MET and 0.017 ng mL-1 for TR. The method has also successfully detected MET and TR in complex biological samples, demonstrating its practical application capabilities. The proposed fluorescent LFIA platform, based on SI/DQD technology, holds significant promise for the swift and accurate POC detection of these substances. Its affordability, compact size, and excellent analytical performance make it suitable for on-site drug testing, including at borders and roadside checks, and open up new possibilities for the design and implementation of drug testing methods.

AIE fluorescent nanozyme-based dual-mode biosensor for analysis of the bioactive component hypoxanthine in meat products

The development of facile, low-cost reliable, and precise onsite assays for the bioactive component hypoxanthine (Hx) in meat products is significant for safeguarding food safety and public health. Herein, we proposed a smartphone-assissted aggregation-induced emission (AIE) fluorogen tetraphenylethene (TPE)-incorporated amorphous Fe-doped phosphotungstates (Fe-Phos@TPE) nanozyme-based ratiometric fluorescence-colorimetric dual-mode biosensor for achieving the onsite visual detection of Hx. When the Hx existed, xanthine oxidase (XOD) catalyzed Hx into H2O2 to be further catalyzed into •OH by the prominent peroxidase activity of Fe-Phos@TPE at pH = 6.5, resulting in the oxidization of nonfluorescent o-phenylenediamine (OPD, naked-eye colorless) to be yellow fluorescent emissive 2,3-diaminophenazine (DAP, naked-eye dark yellow) at 550 nm as well as the intrinsic blue fluorescence of Fe-Phos@TPE at 440 nm to be decreased via inner-filter effect (IFE) action, thereby realizing a multi-enzyme cascade catalytic reaction at near-neutral pH to overcome the traditional acidity dependence-induced time-consuming and low sensitivity troublesome.

Development of pectin-based gel electrolyte for wireless electrochemical determination of cadmium and lead using smartphone

A portable device offering effortlessness, mobility, and affordability for real-time and on-site monitoring of heavy metals is currently in great demand to maintain environmental sustainability. Herein, a platform utilizing a biopolymeric gel-based electrolyte for the on-field simultaneous determination of Cd(II) and Pb(II) is described. Pectin, a natural polymer, was exploited as a chemical delivery medium on account of its biodegradability, environmental friendliness, and rapid dissolving characteristics. The gel electrolyte was prepared by having pectin dissolved in KCl mixed with Sb(III)-Bi(III) bimetallic alloy solution, and casted onto a paper substrate. An in situ bimetallic alloy and pre-mixed bismuth nanoparticles modified screen-printed graphene electrode (Sb-Bi/BiNP/SPGE) were employed to enhance the electrochemical signals of Cd(II) and Pb(II) for the differential pulse anodic stripping voltammetry (DPASV). It was demonstrated that the platform was capable of generating sharp and well-defined current signals, achieving the low detection limits of 50.98 ng mL-1 for Cd(II) and 40.80 ng mL-1 for Pb(II). The reproducibility, as indicated by the relative standard deviation, was found to be less than 10.4 % (n = 10) for the developed gel-based device when coupled with a wireless near field communication (NFC) potentiostat. Lastly, the obtained sensor was applied for quantification of Cd and Pb in potentially contaminated groundwater samples. The recoveries obtained were satisfactorily within the acceptable range. The newly designed platform exhibited several advantages, including small sample volume (μL), low-cost, no sample preparation requirements, and being environmentally friendly. The convenience of a portable device utilizing the proposed biopolymeric gel-based electrolyte for on-field analysis makes it highly appealing for various applications.

Tb3+ assisted dithioerythritol stabilized copper nanocluster with AIE behavior for ratiometric fluorescent determination of fluoroquinolones

BACKGROUND

Fluoroquinolones (FQs) are widely used in livestock and poultry industry because of their satisfactory effects in preventing and treating bacterial infection. However, due to irrational use and poor biodegradability, FQs can easily remain in food animals and further enter the human body through the food chain. Therefore, accurate and sensitive detection of FQs residues in animal-origin food is significant. The traditional methods commonly used for FQs detection have some limitations. Ratiometric fluorescence detection technology has the advantages of fast, sensitive, self-correcting, and easy visualization. However, the reports on the use of ratiometric fluorescence probes for FQs detection are limited.

RESULTS

In this work, a novel probe was proposed for ratiometric fluorescent analysis of FQs. In this probe, the fluorescence of dithioerythritol stabilized copper nanoclusters (DTE-Cu NCs) was significantly enhanced due to the Tb3+ triggered aggregation-induced emission effect. FQs bound Tb3+ in Tb3+/DTE-Cu NCs through carboxyl and carbonyl groups, so that Tb3+ was effectively sensitized to emit green fluorescence. However, the red fluorescence of DTE-Cu NCs was not interfered. The fluorescence of the probe transformed from red to green with the increase of FQs concentration. Using norfloxacin (NOR), difloxacin (DIF), and enrofloxacin (ENR) as FQs simulants, this probe showed a sensitive linear response ranged from 0.025 to 22.5 μM, with the limits of detection of 9.6 nM, 9.3 nM, and 7.7 nM. The application potential for FQs detection was verified via a standard addition assay of egg samples with the recovery rate of 90.4 %-114.7 %.

SIGNIFICANT

The fluorescence probe based on Tb3+/DTE-Cu NCs is expected to realize the ratiometric fluorescence sensitive detection of FQs. The establishment of this simple, effective, and rapid detection platform opens up a new way for the detection of FQs residues in animal-origin foods, and also provides a new idea for the design of rapid detection platforms for other hazard factors.

Intelligent onsite dual-modal assay based on oxidase-like fluorescence carbon dots-driven competitive effect for ethyl carbamate detection

Intelligent onsite accurate monitoring ethyl carbamate (EC, a group 2 A carcinogen) in environment is of great significance to safeguard environmental health and public safety. Herein, we reported an intelligent dual-modal point-of-care (POC) assay based on the bimetallic Mn and Ce co-doped oxidase-like fluorescence carbon dots (Ce&MnCDs) nanozyme-driven competitive effect. In brief, the oxidase-like activity of Ce&MnCDs was inhibited by thiocholine (TCh, originating from the hydrolysis of acetylcholinesterase (AChE) to acetylthiocholine (ATCh)), preventing the oxidation of o-phenylenediamine (OPD) to 2,3-diaminophenothiazine (DAP). However, with the aid of Br2 + NaOH, EC inactivated AChE to prevent TCh generation for re-launching the oxidase-like activity of Ce&MnCDs to trigger the oxidation of OPD into DAP, thereby outputting an EC concentration-dependent ratiometric fluorescence and colorimetric readouts by employing Ce&MnCDs and OPD as the optical signal reporters. Interestingly, these dual-modal optical signals could be transduced into the gray values that was linearly proportional to the residual levels of EC on a smartphone-based portable platform, with a detection limit down to 1.66 μg/mL, qualifying the requirements of analysis of EC residues in real samples. This opened up a new avenue for onsite assessment of the risk of residues of EC, safeguarding environmental health and public safety.

Advances on chalcogenide quantum dots-based sensors for environmental pollutants monitoring

Water contamination represents a significant ecological impact with global consequences, contributing to water scarcity worldwide. The presence of several pollutants, including heavy metals, pharmaceuticals, pesticides, and pathogens, in water resources underscores a pressing global concern, prompting the European Union (EU) to establish a Water Watch List to monitor the level of these substances. Nowadays, the standard methods used to detect and quantify these contaminants are mainly liquid or gas chromatography coupled with mass spectrometry (LC/GC-MS). While these methodologies offer precision and accuracy, they require expensive equipment and experienced technicians, and cannot be used on the field. In this context, chalcogenide quantum dots (QDs)-based sensors have emerged as promising, user-friendly, practical, and portable tools for environmental monitoring. QDs are semiconductor nanocrystals that possess excellent properties, and have demonstrated versatility across various sensor types, such as fluorescent, electrochemical, plasmonic, and colorimetric ones. This review summarizes recent advances (2019-2023) in the use of chalcogenide QDs for environmental sensing, highlighting the development of sensors capable of detect efficiently heavy metals, anions, pharmaceuticals, pesticides, endocrine disrupting compounds, organic dyes, toxic gases, nitroaromatics, and pathogens.

Modernization of digital food safety control

Foodborne illness remains a pressing global issue due to the complexities of modern food supply chains and the vast array of potential contaminants that can arise at every stage of food processing from farm to fork. Traditional food safety control systems are increasingly challenged to identify these intricate hazards. The U.S. Food and Drug Administration's (FDA) New Era of Smarter Food Safety represents a revolutionary shift in food safety methodology by leveraging cutting-edge digital technologies. Digital food safety control systems employ modern solutions to monitor food quality by efficiently detecting in real time a wide range of contaminants across diverse food matrices within a short timeframe. These systems also utilize digital tools for data analysis, providing highly predictive assessments of food safety risks. In addition, digital food safety systems can deliver a secure and reliable food supply chain with comprehensive traceability, safeguarding public health through innovative technological approaches. By utilizing new digital food safety methods, food safety authorities and businesses can establish an efficient regulatory framework that genuinely ensures food safety. These cutting-edge approaches, when applied throughout the food chain, enable the delivery of safe, contaminant-free food products to consumers.

Self-powered molecularly imprinted photoelectrochemical sensor based on Ppy/QD/HOF heterojunction for the detection of bisphenol A

As an emerging porous material, hydrogen-bonded organic framework materials (HOFs) still pose application challenges. In this work, the designed type "I + II" heterojunction extracted hot electrons from HOFs using quantum dots (QDs) and polypyrrole (Ppy), improving the stability and photoelectrochemical performance of materials. In addition to serving as a potential well, electropolymerized Ppy was used as a recognition element for bisphenol A (BPA), and a novel self-powered molecularly imprinted photoelectrochemical (MIP-PEC) sensor was designed. The sensing platform showed a linear relationship from 1 × 10-10 to 1 × 10-7 mol∙L-1 and from 1 × 10-7 to 1 mol∙L-1 with an acceptable detection limit of 4.2 × 10-11 mol∙L-1. This is the first application of HOFs in constructing MIP-PEC sensors and a new attempt to improve the stability of HOFs for the application of porous crystal materials in the sensing field.

Multiplexed colorimetry collaborated with smartphone-based image analysis for simultaneous and fast visualization of dyes in both environmental and food samples

In this work, a multiplexed colorimetric strategy was initiated for simultaneous and fast visualization of dyes using low-cost and easy-to-prepare indicator papers as sorbents. Response surface methodology (RSM) was employed to model statistically and optimize the process variables for dyes extraction and colorimetric assays. Multiplexed colorimetry was realized by virtue of synchronous color alignments from different dimensions of multiple dyes co-stained colorimetric cards under RSM-optimized conditions, and smartphone-based image analysis was subsequently performed from different modes to double-check the credibility of colorimetric assays. As concept-to-proof trials, simultaneous visualization of dyes in both beverages and simulated dye effluents was experimentally proved with results highly matched to HPLC or spiked amounts at RSM-predicted staining time as short as 50 s ∼3 min, giving LODs as low as 0.97 ± 0.22/0.18 ± 0.08 μg/mL (tartrazine/brilliant blue) for multiplexed colorimetry, which much lower than those obtained by single colorimetry. Since this is the first case to propose such a RSM-guided multiplexed colorimetric concept, it will provide a reference for engineering of other all-in-one devices which can realize synchronous visualization applications within limited experimental steps.

Development of a sustainable procedure for smartphone-based colorimetric determination of benzalkonium chloride in pharmaceutical preparations

A sustainable procedure offering green, simple, and rapid analysis was developed to determine benzalkonium chloride (BKC) in pharmaceutical preparations. The determination using smartphones was based on the ion pair colorimetric reaction with bromothymol blue (BTB), which produces a yellow color. The intensity of the product color, which is proportional to the concentration of BKC, was detected and evaluated using a smartphone camera and an image processing application. The procedure was performed in a microliter and was rapidly detected within 1 min after incubation. This offered high throughput at 28 samples per well plate in duplicate. Linear calibration, which was a plot of BKC concentrations and relative red intensities, was in the range of 2.0-24.0 μg/mL with an R2 of 0.997. The limits of detection (LOD) and quantitation (LOQ) were 1.0 and 3.2 μg/mL, respectively. This work was successful in applying it to pharmaceutical materials, disinfectant products, and pharmaceutical products containing BKC. It was discovered that the concentrations of BKC as an active ingredient in pharmaceutical materials were 82% w/v, whereas those in disinfectant products ranged from 0.4 to 2.1% w/v. In pharmaceutical products, ophthalmic drops and nasal sprays contain BKC as preservatives in the 0.01-0.02, and the 0.02% w/v, respectively. The results obtained by the proposed procedure compared with a reference titration method showed no significant differences at a 95% confidence level with 1.2-3.4% RSDs. This promotes the efficiency of pharmaceutical preparations regarding infection prevention and control by ensuring that available disinfectants contain a sufficient concentration of BKC. Additionally, this improves the efficiency of pharmaceutical preparations for quality control of pharmaceutical products by ensuring that the available preservatives maintain a sufficient concentration throughout the lifespan of the products.

A highly sensitive and selective fluorescent biosensor for breast cancer derived exosomes using click reaction of azide-CD63 aptamer and alkyne-polymer dots

Exosomes have gained recognition as valuable reservoirs of biomarkers, holding immense potential for early cancer detection. Consequently, there is a pressing need for the development of an economical and highly sensitive exosome detection methodology. In this work, we present a fluorescence method for breast cancer-derived exosome detection based on Cu-triggered click reaction of azide-modified CD63 aptamer and alkyne functionalized Pdots. The detection threshold for the exosomes obtained from the breast cancer serum was determined to be 6.09 × 107 particles per μL, while the measurable range spanned from 6.50 × 107 to 1.30 × 109 particles per μL. The employed methodology achieved notable success in accurately distinguishing breast cancer patients from healthy individuals through serum analysis. The application of this method showcases the significant potential for early exosome analysis in the clinical diagnosis of breast cancer patients.

A portable smartphone-assisted Tb-MOF-based agar-slice probe for the rapid and on-site fluorescence assay of malachite green in aquatic products

In this study, a new Tb-MOF fluorescence probe was developed for the detection of malachite green (MG) in real aquatic products. Fluorescence sensing experiments revealed that MG can effectively quench the green fluorescence of Tb-MOF suspensions, and the detection process exhibits the advantages of high sensitivity, a wide linear range (0-80 μM), a low detection limit (10.8 nM) and a rapid response time. Selective detection of MG is achieved primarily through fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) mechanisms. Furthermore, a smartphone-assisted Tb-MOF-based agar slice detection platform was constructed for the visual and quantitative detection of MG. Additionally, the on-site detection of MG in crucian and shrimp samples was accomplished with high recoveries (99.8 %-107.99 %) and low relative standard deviations (RSD < 2.2 %). This developed detection platform introduced a low-cost, portable and user-friendly approach for MG detection.

Potential toxic effects of perfluorobutanesulfonyl fluoride analysis based on multiple-spectroscopy techniques and molecular modelling analysis

Perfluorobutanesulfonyl fluoride (PBSF) has been used in the manufacture of fluorochemicals. Since PBSF is not biodegradable, the predicted environmental levels of PBSF are also expected to rise over time. In recent years, there has been a rise in the levels of PBSF in humans. In order to clarify the impact of PBSF on the accumulation of substances in the human body, we examined the interaction mechanism between PBSF and bovine serum albumin (BSA). To investigate the interaction mechanism between PBSF and BSA, we utilized a range of methods including UV-visible spectrophotometry, fluorescence spectroscopy, circular dichroism, molecular docking simulation, and molecular dynamics (MD) simulation. The inherent fluorescence of BSA was effectively suppressed by PBSF through fluorescence quenching analysis, using a static mechanism. The Ka value of 1.34 × 105 mol-1 L indicated a strong binding between PBSF and BSA. Further analysis of the interaction between PBSF and BSA involved examining thermodynamic parameters, fluorescence resonance energy transfer, and conducting other theoretical calculations. These investigations produced results that were in strong accordance with the experimental observations. The participation of hydrophobic interactions between BSA and PBSF was uncovered through molecular docking and MD simulation investigations. Furthermore, this investigation explored the impact of copper ions (Cu2+) and calcium ions (Ca2+) on the interaction between PBSF and BSA, establishing a vital basis for comprehending the mechanism by which PBSF affects proteins in the human surroundings.

A portable colorimetric sensing platform for rapid and sensitive quantification of dichlorvos pesticide based on Fe-Mn bimetallic oxide nanozyme-participated highly efficient chromogenic catalysis

BACKGROUND

Dichlorvos (DDVP), as a highly effective insecticide, is widely used in agricultural production. However, DDVP residue in foodstuffs adversely affects human health. Conventional instrumental analysis can provide highly sensitive and accurate detection of DDVP, while the need of bulky and expensive equipment limits their application in resource-poor areas and on-site detection. Therefore, the development of easily portable sensing platforms for convenient, rapid and sensitive quantification of DDVP is very essential for ensuring food safety.

RESULT

A portable colorimetric sensing platform for rapid and sensitive quantification of DDVP is developed based on nanozyme-participated highly efficient chromogenic catalysis. The Fe-Mn bimetallic oxide (FeMnOx) nanozyme possesses excellently oxidase-like activity and can efficiently catalyze oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) into a blue oxide with a very low Michaelis constant (Km) of 0.0522 mM. The nanozyme-catalyzed chromogenic reaction can be mediated by DDVP via inhibiting the acetylcholinesterase (AChE) activity. Thus, trace DDVP concentration-dependent color evolution is achieved and DDVP can be sensitively detected by spectrophotometry. Furthermore, a smartphone-integrated 3D-printed miniature lightbox is fabricated as the colorimetric signal acquisition and processing device. Based on the FeMnOx nanozyme and smartphone-integrated lightbox system, the portable colorimetric sensing platform of DDVP is obtained and it has a wide linear range from 1 to 3000 ng mL-1 with a low limit of detection (LOD) of 0.267 ng mL-1 for DDVP quantification.

SIGNIFICANCE

This represents a new portable colorimetric sensing platform that can perform detection of DDVP in foodstuffs with simplicity, sensitivity, and low cost. The work not only offers an alternative to rapid and sensitive detection of DDVP, but also provides a new insight for the development of advanced sensors by the combination of nanozyme, 3D-printing and information technologies.

Design of Highly Efficient Electronic Energy Transfer in Functionalized Quantum Dots Driven Specifically by Ethylenediamine

The exploration of emerging functionalized quantum dots (QDs) through modulating the effective interaction between the sensing element and target analyte is of great significance for high-performance trace sensing. Here, the chromone-based ligand grafted QDs (QDs-Chromone) were initiated to realize the electronic energy transfer (EET) driven specifically by ethylenediamine (EDA) in the absence of spectral overlap. The fluorescent and colorimetric dual-mode responses (from red to blue and from colorless to yellow, respectively) resulting from the expanded conjugated ligands reinforced the analytical selectivity, endowing an ultrasensitive and specific response to submicromolar-liquid of EDA. In addition, a QDs-Chromone-based sensing chip was constructed to achieve the ultrasensitive recognition of EDA vapor with a naked-eye observed response at a concentration as low as 10 ppm, as well as a robust anti-interfering ability in complicated scenarios monitoring. We expect the proposed EET strategy in shaping functionalized QDs for high-performance sensing will shine light on both rational probe design methodology and deep sensing mechanism exploration.

Fluorescent and smartphone imaging detection of tetracycline residues based on luminescent europium ion-functionalized the regular octahedral UiO-66-NH2

Antibiotic residues cause extensive damage to food security, thus arousing serious concerns. Hence, rapid and sensitive detection of antibiotic residues is crucial to food safety. This study aimed to propose a portable, visual, intelligent and rapid method for tetracycline detection. We developed a ratiometric fluorescent sensor based on the Eu3+-functionalized regular octahedral UiO-66-NH2 material. The developed sensor could quantify tetracycline in the concentration range of 0.5-200 μM with a detection limit as low as 0.2 μM under the optimum conditions. Furthermore, the analytical results obtained using the designed sensor in the actual samples were basically consistent with those obtained using high-performance liquid chromatography. Based on these achievements, a smartphone application-integrated fluorescent testing paper was designed for facile, intelligent, and visual detection of tetracycline. The integrated portable sensor not only saved cost and time for testing but also provided a forward-looking approach to fast, sensitive detection of antibiotic residues.

The construction of dual-emissive ratiometric fluorescent probes based on fluorescent nanoparticles for the detection of metal ions and small molecules

With the rapid development of fluorescent nanoparticles (FNPs), such as CDs, QDs, and MOFs, the construction of FNP-based probes has played a key role in improving chemical sensors. Ratiometric fluorescent probes exhibit distinct advantages, such as resistance to environmental interference and achieving visualization. Thus, FNP-based dual-emission ratiometric fluorescent probes (DRFPs) have rapidly developed in the field of metal ion and small molecule detection in the past few years. In this review, firstly we introduce the fluorescence sensing mechanisms; then, we focus on the strategies for the fabrication of DRFPs, including hybrid FNPs, single FNPs with intrinsic dual emission and target-induced new emission, and DRFPs based on auxiliary nanoparticles. In the section on hybrid FNPs, methods to assemble two types of FNPs, such as chemical bonding, electrostatic interaction, core satellite or core-shell structures, coordination, and encapsulation, are introduced. In the section on single FNPs with intrinsic dual emission, methods for the design of dual-emission CDs, QDs, and MOFs are discussed. Regarding target-induced new emission, sensitization, coordination, hydrogen bonding, and chemical reaction induced new emissions are discussed. Furthermore, in the section on DRFPs based on auxiliary nanoparticles, auxiliary nanomaterials with the inner filter effect and enzyme mimicking activity are discussed. Finally, the existing challenges and an outlook on the future of DRFP are presented. We sincerely hope that this review will contribute to the quick understanding and exploration of DRFPs by researchers.

Octahedral Cu2O nanomaterials as electrochemical aptasensor for sensitive detection of tetracycline in milk

In this work, A novel label-free electrochemical biosensor based on octahedral Cu2O @ Au nanocomposites was developed for the detection of tetracycline. The gold nanoparticles (AuNPs) on the surface of Cu2O nanomaterials not only improve the electrochemical performance, but also can be used as a binding site for thiol-modified tetracycline aptamers, which can specifically bind to tetracycline. Cu2O @ Au nanocomposites provide a synergistic effect of electrochemical signal amplification and tetracycline recognition strategy. Under the optimal conditions, the proposed biosensor exhibited different electrochemical reactions for different concentrations of tetracycline, with a linear range of 1 nM-1000 μM and a detection limit of 0.16 nM. This work provides a new idea for rapid and sensitive detection of tetracycline by using a simple and economical tetracycline aptamer combined with Cu2O @ Au biosensor platform.

A fluorescent method for bisphenol A detection based on enzymatic oxidation-mediated emission quenching of silicon nanoparticles

As a common raw material of industrial products, bisphenol A (BPA) is widely used in the production of food contact materials, and there is a high risk of exposure in food. However, BPA is a well-known endocrine disruptor and poses a serious threat to human health. Herein, a fluorescent sensing platform of BPA based on enzymatic oxidation-mediated fluorescence quenching of silicon nanoparticles (SiNPs) is established and used to the detection of BPA in food species. The SiNPs are prepared with a facile one-step synthesis and emit bright green fluorescence. BPA can be oxidized by horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) to form a product which can quench the fluorescence of SiNPs through electron transfer. There is a good linear relationship between the fluorescence intensity and BPA concentration in the range of 1-100 μM. Therefore, a fluorometry of BPA is established with a low limit of detection (LOD) of 0.69 μM. This method has been applied to the determination of BPA in mineral drinking water, orange juice, and milk with satisfactory results. The fluorescent sensor of BPA based on SiNPs has favorable application foreground in the field of food safety analysis.

Facile preparation of dihydrolipoic acid-stabilized red-emitting silver nanoclusters as a sensitive fluorometric probe for sulfide ions detection

In this work, we report a smartphone-integrated paper-based sensor for the determination of sulfide ions (S2-) using water-soluble dihydrolipoic acid stabilized silver nanoclusters (DHLA-AgNCs) as a nanoprobe. The optical properties of red emitting fluorescent DHLA-AgNCs was confirmed by UV-visible, steady state flourometric spectroscopic studies. The HR-TEM analysis revealed that the morphology of DHLA-AgNCs was quasi spherical with a grain size of ∼ 5.2 nm. The DHLA-AgNCs exhibited bright red luminescence with strong emission band centered at 650 nm upon the excitation at 420 nm. The excellent fluorescence property of DHLA-AgNCs was further utilized for fluorometric determination of S2- ions. The DHLA-AgNCs can be effectively quenched by increasing concentration of S2- ions owing to the formation of Ag2S complex. The DHLA-AgNCs probe could detect S2- ions preferentially even in the presence of other possible interfering anions with a limit of detection of 32.71 nM. In addition, the proposed technique was effectively used to detect S2- ions in environmental water samples such as tap and drinking water. The detect S2- ions detection was assay and showed good agree compared with the conventional methylene blue approach and showed comparable results. Moreover, a smartphone-paper-based detection assay was developed using the DHLA-AgNCs probe for highly selective and sensitive determination of S2- ions.

Advancing biological investigations using portable sensors for detection of sensitive samples

Portable biosensors are emerged as powerful diagnostic tools for analyzing intricately complex biological samples. These biosensors offer sensitive detection capabilities by utilizing biomolecules such as proteins, nucleic acids, microbes or microbial products, antibodies, and enzymes. Their speed, accuracy, stability, specificity, and low cost make them indispensable in forensic investigations and criminal cases. Notably, portable biosensors have been developed to rapidly detect toxins, poisons, body fluids, and explosives; they have proven invaluable in forensic examinations of suspected samples, generating efficient results that enable effective and fair trials. One of the key advantages of portable biosensors is their ability to provide sensitive and non-destructive detection of forensic samples without requiring extensive sample preparation, thereby reducing the possibility of false results. This comprehensive review provides an overview of the current advancements in portable biosensors for the detection of sensitive materials, highlighting their significance in advancing investigations and enhancing sensitive sample detection capabilities.

QD-based fluorescent nanosensors: Production methods, optoelectronic properties, and recent food applications

Food quality and safety are crucial public health concerns with global significance. In recent years, a series of fluorescence detection technologies have been widely used in the detection/monitoring of food quality and safety. Due to the advantages of wide detection range, high sensitivity, convenient and fast detection, and strong specificity, quantum dot (QD)-based fluorescent nanosensors have emerged as preferred candidates for food quality and safety analysis. In this comprehensive review, several common types of QD production methods are introduced, including colloidal synthesis, self-assembly, plasma synthesis, viral assembly, electrochemical assembly, and heavy-metal-free synthesis. The optoelectronic properties of QDs are described in detail at the electronic level, and the effect of food matrices on QDs was summarized. Recent advancements in the field of QD-based fluorescent nanosensors for trace level detection and monitoring of volatile components, heavy metal ions, food additives, pesticide residues, veterinary-drug residues, other chemical components, mycotoxins, foodborne pathogens, humidity, and temperature are also thoroughly summarized. Moreover, we discuss the limitations of the QD-based fluorescent nanosensors and present the challenges and future prospects for developing QD-based fluorescent nanosensors. As shown by numerous publications in the field, QD sensors have the advantages of strong anti-interference ability, convenient and quick operation, good linear response, and wide detection range. However, the reported assays are laboratory-focused and have not been industrialized and commercialized. Promising research needs to examine the potential applications of bionanotechnology in QD-based fluorescent nanosensors, and focus on the development of smart packaging films, labeled test strips, and portable kits-based sensors.

Current and Future Technologies for the Detection of Antibiotic-Resistant Bacteria

Antibiotic resistance is a global public health concern, posing a significant threat to the effectiveness of antibiotics in treating bacterial infections. The accurate and timely detection of antibiotic-resistant bacteria is crucial for implementing appropriate treatment strategies and preventing the spread of resistant strains. This manuscript provides an overview of the current and emerging technologies used for the detection of antibiotic-resistant bacteria. We discuss traditional culture-based methods, molecular techniques, and innovative approaches, highlighting their advantages, limitations, and potential future applications. By understanding the strengths and limitations of these technologies, researchers and healthcare professionals can make informed decisions in combating antibiotic resistance and improving patient outcomes.

Surface imprinted-covalent organic frameworks for efficient solid-phase extraction of fluoroquinolones in food samples

Molecularly imprinting on covalent organic frameworks (MI-COF) is a promising way to prepare selective adsorbents for effective extraction of fluoroquinolones (FQs). However, the unstable framework structure and complex imprinting process are challenging for the construction of MI-COF. Here, we report a facile surface imprinting approach with dopamine to generate imprinted cavities on the surface of irreversible COF for highly efficient extraction of FQs in food samples. The irreversible-linked COF was fabricated from hexahydroxytriphenylene and tetrafluorophthalonitrile to ensure COF stability. Moreover, the introduction of dopamine surface imprinted polymer into COF provides abundant imprinted sites and endows excellent selectivity for FQs recognition against other antibiotics. Taking enrofloxacin as a template molecule, the prepared MI-COF gave an exceptional adsorption capacity of 581 mg g-1, a 2.2-fold enhancement of adsorption capacity compared with nonimprinted COF. The MI-COF was further explored as adsorbent to develop a novel solid-phase extraction method coupled with high-performance liquid chromatography for the simultaneous determination of enrofloxacin, norfloxacin and ciprofloxacin. The developed method gave the low limits of detection at 0.003-0.05 ng mL-1, high precision with relative standard deviations less than 3.5%. The recoveries of spiked FQs in food samples ranged from 80.4% to 110.7%.

Integrated Design of a Dual-Mode Colorimetric Sensor Driven by Enzyme-like Activity Regulation Strategy for Ultratrace and Portable Detection of Hg2

Colorimetric analysis for mercury detection has great application potential in the prevention of health damage caused by mercury in the environment. Sensitivity, selectivity, and portability are core competencies of sensors, and concentrating these properties in a single sensor for efficient mercury detection remains a great challenge. Herein, a hollow structure CuS@CuSe@PVP (CCP) was prepared in which the enzyme-like activities could be activated by Hg2+ due to the antagonism between Hg and Se, inspiring the establishment of a colorimetric method for Hg2+ detection. As for Hg2+ detection performance, the linear range (LR) and limit of detection (LOD) were 1-900 and 0.81 nM in the POD-like activity system, respectively. Also, 5-550 nM of LR and 2.34 nM of LOD were achieved in the OD-like activity system. Further, a smartphone-mediated portable RGB nanosensor was fabricated, with a LOD down to 6.65 nM in the POD-like system and 7.97 nM in the OD-like system. Moreover, the excellent self-calibration and satisfactory recovery of 94.77%-106.16% were shown in the application of real water samples analysis. This study represented advanced progress toward emerging applications of nanozymes with multiple enzyme-like activities in heavy metal detection and will accelerate the development of efficient and portable heavy metal sensors.

Carrier-Free Binary Self-Assembled Nanomedicines Originated from Traditional Herb Medicine with Multifunction to Accelerate MRSA-Infected Wound Healing by Antibacterial, Anti-Inflammation and Promoting Angiogenesis

Background

Deaths from bacterial infections have risen year by year. This trend is further aggravated as the overuse antibiotics and the bacterial resistance to all known antibacterial agents. Therefore, new therapeutic alternatives are urgently needed.

Methods

Enlightenment the combination usage of traditional herb medicine, one carrier-free binary nanoparticles (GA-BBR NPs) was discovered, which was self-assembled from gallic acid and berberine through electrostatic interaction, π-π stacking and hydrophobic interaction; and it could be successfully prepared by a green, cost-effective and "one-pot" preparation process.

Results

The nanoparticles exhibited strong antibacterial activity and biofilm removal ability against multidrug-resistant S. aureus (MRSA) by downregulating mRNA expression of rpsF, rplC, rplN, rplX, rpsC, rpmC and rpsH to block bacterial translation mechanisms in vitro and in vivo, and it had well anti-inflammatory activity and a promising role in promoting angiogenesis to accelerate the wound healing on MRSA-infected wounds model in vivo. Additionally, the nanoparticles displayed well biocompatibility without cytotoxicity, hemolytic activity, and tissue or organ toxicity.

Conclusion

GA-BBR NPs originated from the drug combination has potential clinical transformation value, and this study provides a new idea for the design of carrier-free nanomedicine derived from natural herbals.

Sensitive detection of cadmium ions based on a quantum-dot-mediated fluorescent visualization sensor

A sensitive ratiometric fluorescent sensor for detecting cadmium ions (Cd2+) was constructed based on carbon quantum dots (CQDs)/CdTe quantum dots (CdTe QDs). Red fluorescence (from CdTe QDs) played the role of the signal response and blue fluorescence (from CQDs) served as a reference probe without a color change. The fluorescent sensor showed high selectivity and sensitivity to Cd2+ with a limit of detection (LOD) of 0.018 μM and a range from 0.1 μM to 23 μM. The proposed method was successfully applied to the determination of Cd2+ in real rice samples. In addition, a fluorescent sensor integrated with a smartphone platform was further designed for the visualized and quantitative detection of Cd2+. This work might extend the range of visualization analysis strategies and provide new insights into the rapid quantitative, portable and sensitive detection of Cd2+ in real-time and on-site applications.

Molecular imprinting-based ratiometric fluorescence sensors for environmental and food analysis

Environmental protection and food safety are closely related to the healthy development of human society; there is an urgent need for relevant analytical methods to determine environmental pollutants and harmful substances in food. Molecular imprinting-based ratiometric fluorescence (MI-RFL) sensors, constructed by combining molecular imprinting recognition and ratiometric fluorescence detection, possess remarkable advantages such as high selectivity, anti-interference ability, high sensitivity, non-destruction and convenience, and have attracted increasing interest in the field of analytical determination. Herein, recent advances in MI-RFL sensors for environmental and food analysis are reviewed, aiming at new construction strategies and representative determination applications. Firstly, fluorescence sources and possible sensing principles are briefly outlined. Secondly, new imprinting techniques and dual/ternary-emission fluorescence types that improve sensing performances are highlighted. Thirdly, typical analytical applications of MI-RFL sensors in environmental and food samples are summarized. Lastly, the challenges and perspectives of the MI-RFL sensors are proposed, focusing on improving sensitivity/visualization and extending applications.

Current Trends in Nanomaterials-Based Electrochemiluminescence Aptasensors for the Determination of Antibiotic Residues in Foodstuffs: A Comprehensive Review

Veterinary pharmaceuticals have been recently recognized as newly emerging environmental contaminants. Indeed, because of their uncontrolled or overused disposal, we are now facing undesirable amounts of these constituents in foodstuff and its related human health concerns. In this context, developing a well-organized environmental and foodstuff screening toward antibiotic levels is of paramount importance to ensure the safety of food products as well as human health. In this case, with the development and progress of electric/photo detecting, nanomaterials, and nucleic acid aptamer technology, their incorporation-driven evolving electrochemiluminescence aptasensing strategy has presented the hopeful potentials in identifying the residual amounts of different antibiotics toward sensitivity, economy, and practicality. In this context, we reviewed the up-to-date development of ECL aptasensors with aptamers as recognition elements and nanomaterials as the active elements for quantitative sensing the residual antibiotics in foodstuff and agriculture-related matrices, dissected the unavoidable challenges, and debated the upcoming prospects.

Butanol accelerated entropy-driven DNA walking machine for rapid and ultrasensitive determination of alkaline phosphatase activity

Alkaline phosphatase (ALP) as an important biomarker as well as an index for the pasteurization degree of dairy food. However, there is a dilemma between the sensitivity and time-cost of ALP determination based on nucleic acid amplification approach. Herein, an ultrasensitive and rapid detection method for the ALP assay was developed based on entropy-driven DNA machine. In our design, the ALP catalyzed dephosphorylation of detection probe, which inhibited the digestion effect of lambda exonuclease. The remaining probe as a linker to tether the walking strand proximity to the surface of track strand modified gold nanoparticle, activating entropy-driven DNA machine. Accompany with walking strand moving, a large amount of assembled dye-labelled strand dissociated from gold nanoparticle with fluorescence recovery. More importantly, to further improve the walking efficiency, butanol was introduced to accelerated the signal amplification at interface, which short the incubation time from several hours to 5 min. Under the optimum condition, the change of fluorescence intensity was proportion to the concentration of ALP in the range from 0.05 U L^-1 to 5 U L^-1 with an ultralow limit of detection of 2.07 × 10^-3 U L^-1 was achieved, which is superior to other reported methods. Furthermore, the proposed method also successfully applied for the spiked milk sample assay with satisfactory recovery in the range of 98.83%-103.00%. This work proposed a new strategy for the application of entropy-driven DNA machine in the field of rapid and ultrasensitive detection.

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.

Novel biosensor platform for glucose monitoring via smartphone based on battery-less NFC potentiostat

Near-field communication (NFC) was used to control a portable glucose biosensor for diabetes diagnosis. The system comprised a smartphone and an NFC potentiostat connected to a screen-printed carbon electrode (SPCE) modified with Prussian blue-graphene ink and functionalized with gold nanoparticles-embedded poly (3,4ethylene dioxythiophene):polysulfonic acid coated with glucose oxidase (GOx-AuNPs-PEDOT:PSS/PB-G). GOx catalyzed the glucose redox reaction while the conductivity and sensitivity of the AuNPs-PEDOT:PSS composite enhanced electron transfer to the PB-G, which was used as a mediator. The fabrication process was characterized by scanning electron microscopy (SEM) with energy dispersibe x-ray analysis (EDX). The platform was electrochemically characterized by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The NFC biosensing device was then applied to quantify glucose in human blood serum by amperometry. The linear concentration range and detection limit for glucose were 0.5-500 μM and 0.15 μM, respectively. The accuracy of the device was good and results were in agreement with the results obtained from the standard hospital method. This NFC glucose sensing device can be a simple, sensitive, selective and portable platform for medical diagnosis.

Rapid Testing of Δ9-Tetrahydrocannabinol and Its Metabolite On-Site Using a Label-Free Ratiometric Fluorescence Assay on a Smartphone

Excessive consumption of Δ9-tetrahydrocannabinol (THC) severely endangers human health and has raised public safety concerns. However, its quantification by readily rapid tools with simplicity and low cost is still challenging. Herein, we found that a G-rich THC aptamer (THC1.2) can tightly bind to thioflavin T (ThT) with strong fluorescence, which would be specifically quenched in the presence of THC. Based on that, a label-free ratiometric fluorescent sensor for the sensing of THC and its metabolite (THC-COOH) based on THC1.2/ThT as a color emitter and red CdTe quantum dots as reference fluorescence was constructed. Notably, a transition of the fluorescent color of the ratiometric probe from green to red can be instantly observed upon the increased concentration of THC and THC-COOH. Furthermore, a portable smartphone-based fluorescence device integrated with a self-programmed Python program was fabricated and used to accomplish on-site monitoring of THC and THC-COOH within 5 min. Under optimized conditions, this ratiometric fluorescent sensor allowed for an instant response toward THC and its metabolite with considerable limits of detection of 97 and 254 nM, respectively. The established sensor has been successfully applied to urine and saliva samples and exhibited satisfactory recoveries (88-116%). This ratiometric fluorescent sensor can be used for the simultaneous detection of THC and THC-COOH with the advantages of rapidness, low cost, ease of operation, and portability, providing a promising strategy for on-site detection and facilitating law enforcement regulation and roadside control of THC.

A smartphone-based fluorospectrophotometer and ratiometric fluorescence nanoprobe for on-site quantitation of pesticide residue

Cost-effective and user-friendly quantitation at points-of-need plays an important role in food safety inspection, environmental monitoring, and biomedical analysis. This study reports a stand-alone smartphone-based fluorospectrophotometer (the SBS) installed with a custom-designed application (the SBS-App) for on-site quantitation of pesticide using a ratiometric sensing scheme. The SBS can collect fluorescence emission spectra in the wavelength range of 380-760 nm within 5 s. A ratiometric fluorescence probe is facilely prepared by directly mixing the blue-emissive carbon nanodots (the Fe3+-specific fluorometric indicator) and red-emissive quantum dots (the internal standard) at a ratio of 11.6 (w/w). Based on the acetylcholinesterase/choline oxidase dual enzyme-mediated cascade catalytic reactions of Fe2+/Fe3+ transformation, a ratiometric fluorescence sensing scheme is developed. The practicability of the SBS is validated by on-site quantitation of chlorpyrifos in apple and cabbage with a comparable accuracy to the GC-MS method, offering a scalable solution to establish a cost-effective surveillance system for pesticide pollution.

A novel smartphone-integrated binary-emission molecularly imprinted fluorescence sensor embedded with MIL-101(Cr) for sensitive and real-time detection of protein

Aiming for precise, real-time, and on-site analysis of proteins, an innovative binary-emission fluorescence imprinted polymer was designed by sol-gel method after mixing MIL-101(Cr), green CdTe (g-CdTe) and red CdTe (r-CdTe) for detection of protein. In this proposal, MIL-101(Cr), as a favorable supporter, provided high surface area and porosity for imprinting sites, which ameliorated the transfer rate and the sensitivity of the nanosensor. And g-CdTe and r-CdTe were served as signal transduction for dual-emission response. Based on strengthened recognition reaction between high-affinity imprinting sites and protein, the fluorescence intensities of g-CdTe and r-CdTe yielded conspicuous two responses at 528 nm and 634 nm for protein under the excitation of 350 nm. The cytochrome c (Cyt c) and trypsin were served as model proteins to verify the generality of strategy. Given prominent merits of MIL-101(Cr), g-CdTe/r-CdTe@MIL-101(Cr)@MIP exhibited good linear range of 1-30 μM for Cyt c and 0.15-4 μM for trypsin, and the limit of detection were 0.13 μM and 0.014 μM, respectively. Significantly, an unsophisticated smartphone-based sensing device was developed by integrating g-CdTe/r-CdTe@MIL-101(Cr)@MIP with a 3D printing portable device to obtain precise on-site results. As expected, this portable platform was successfully applied for monitoring Cyt c and trypsin with a detection limit of 0.71 μM and 0.026 μM, respectively. These results indicated this dual-response molecularly imprinted fluorescence senor based on smartphone provided promising perspectives on futural on-site protein analysis.

Multi-color fluorescence sensing platform for visual determination of norfloxacin based on a terbium (Ш) functionalized covalent organic framework

Sensitive and visual determination of fluoroquinolone antibiotics (FQs) is of great significance since their abuse and inappropriate handling can be problematic. Herein, we propose a lanthanide covalent organic framework fluorescence sensing system (Tb@COF-Ru) with visualization capability to determine the FQs level, where Tb@COF was employed as the sensing probe, while the red-emitting Ru(bpy)₃²⁺ serves as a constant red fluorescent background. With increasing norfloxacin concentration, the green fluorescence of Tb³⁺ is gradually enhanced, finally realizing the multicolor fluorescence change from red to green. With a smartphone for RGB analysis, visual monitoring and quantitative analysis were realized without any sophisticated instrument. Limits of detection for the fluorescence quantitative and visual mode for norfloxacin were 0.33 nM and 7.3 μM, respectively. This method was rapid (1 min) and visualized, providing a simple analysis of various food matrices (honey, milk, egg and beef) and water samples for trace FQs.

Developing an analytical framework for estimating food security indicators in the United Arab Emirates: A review

Rapid population growth, climate change, limited natural resources, and the COVID-19 pandemic contribute to increased global hunger, necessitating intensive efforts to ensure food security and nutrition (FSN). Previous FSN approaches covered some dimensions, but not all, resulting in significant gaps in food security indicators. The Gulf Cooperation Council (GCC) and the Middle East and North Africa (MENA) regions have received less attention in food security studies, thus far necessitating considerable effort to develop an appropriate analytical framework. This study reviewed articles and international reports of FSN indicators, drivers and policies, methods, and models and extracted the challenges and gaps from the global and UAE contexts. The UAE and the world have gaps in FSN drivers, indicators, and methods, necessitating potential solutions to meet future challenges such as rapid population growth, pandemics, and limited natural resources. As a result, we created a newly developed analytical framework that addresses the shortcomings of previous approaches such as sustainable food systems developed by FAO and the Global Food Security Index (GFSI) and covers all aspects of food security. Gaps in knowledge in FSN drivers and policies, indicators, big data, methods, and models were considered in the developed framework, which has specific advantages. The novel developed framework addresses all food security dimensions (access, availability, stability, and utilization), ensuring poverty reduction, food security, and nutrition security while outperforming previous approaches (i.e., FAO and GFSI). The developed framework could be used successfully not only in the UAE and MENA, but also, globally, helping to solve food insecurity and malnutrition for future generations. The scientific community and policymakers should disseminate such solutions to address global food insecurity and ensure nutrition for future generations in the face of rapid population growth, limited natural resources, climate change, and spreading pandemics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10668-023-03032-3.

A smartphone-assisted optosensing platform based on chromium-based metal-organic framework signal amplification for ultrasensitive and real-time determination of oxytetracycline

Ultrasensitive and onsite detection of oxytetracycline (OTC) is of vital significance for ensuring public health. Herein, a novel and versatile fluorescence biomimetic nanosensor, Mg,N-CDs@MIL-101@MIP, was elaborately tailored for the assay of OTC. MIL-101 with extraordinarily high surface area and porosity, as a favorable supporter, suppressed self-quenching of Mg,N-CDs and boosted mass transfer rate, realizing signal amplification. As an ultrasensitive signal transducer, high luminescent Mg,N-CDs yielded conspicuous fluorescence responses for OTC, enhancing the sensitivity of Mg,N-CDs@MIL-101@MIP. High-affinity imprinting sites further endowed Mg,N-CDs@MIL-101@MIP with superior anti-interference ability and reusability. Given prominent merits, Mg,N-CDs@MIL-101@MIP demonstrated a good linear range (0.05-40 μg mL^-1) with a lower limit of detection (16.8 ng mL^-1), supplying high accessibility to realize ultrasensitive and highly selective measurement of OTC in samples. Additionally, to attain precise onsite profiling of OTC, an intelligent sensing platform was developed by integrating Mg,N-CDs@MIL-101@MIP with a portable smartphone-assisted optical device. As both signal reader and analyzer, smartphone can instantly capture concentration-dependent fluorescent images and accurately digitize them, accomplishing quantitative analysis of OTC. More delightfully, the portable platform was utilized for visual determination of OTC in milk samples with satisfactory results, offering a promising tool for the high-performance onsite evaluation of food safety and environmental health.

Engineering an Enzymatic Cascade Catalytic Smartphone-Based Sensor for Onsite Visual Ratiometric Fluorescence-Colorimetric Dual-Mode Detection of Methyl Mercaptan

Precise and reliable onsite detection of methyl mercaptan (CH₃SH) is of great significance for environmental surveillance. Here, we synthesized a novel blue fluorescence nanozyme CeO₂@TPE with high peroxidase-like activity by employing aggregation-induced emission (AIE) tetraphenylethene (TPE) to embed into hollow CeO₂ nanospheres. In the presence of ethanol oxidase (AOX) and o-phenylenediamine (OPD), we engineered an enzymatic cascade activation ratiometric fluorescence-colorimetric dual-mode system AOX/CeO₂@TPE + OPD toward CH₃SH. In this design, CH₃SH initiated AOX catalytic activity to convert it into H₂O₂ for activating the peroxidase-like activity of CeO₂@TPE, producing ^•OH for oxidizing the naked-eye colorless OPD into deep yellow 2,3-diaminophenazine (DAP) with an absorption enhancement at ∼425 nm, companied by a new emission peak at ∼550 nm to match with the intrinsic emission at ∼441 nm for observing ratiometric fluorescence response, enabling a ratiometric fluorescence-colorimetric dual-mode analysis. Interestingly, both the ratiometric fluorescence and colorimetric signals could be gathered for being converted into the hue parameter on a smartphone-based sensor, achieving the onsite visual fluorescence-colorimetric dual-mode detection of CH₃SH in real environmental media with acceptable results. This study gave a novel insight into designing target-responsive enzymatic cascade activation system-based efficient and reliable dual-mode point-of-care sensors for safeguarding environmental health.

Smartphone-Facilitated Mobile Colorimetric Probes for Rapid Monitoring of Chemical Contaminations in Food: Advances and Outlook

Smartphone-derived colorimetric tools have the potential to revolutionize food safety control by enabling citizens to carry out monitoring assays. To realize this, it is of paramount significance to recognize recent study efforts and figure out important technology gaps in terms of food security. Driven by international connectivity and the extensive distribution of smartphones, along with their built-in probes and powerful computing abilities, smartphone-based sensors have shown enormous potential as cost-effective and portable diagnostic scaffolds for point-of-need tests. Meantime, the colorimetric technique is of particular notice because of its benefits of rapidity, simplicity, and high universality. In this study, we tried to outline various colorimetric platforms using smartphone technology, elucidate their principles, and explore their applications in detecting target analytes (pesticide residues, antibiotic residues, metal ions, pathogenic bacteria, toxins, and mycotoxins) considering their sensitivity and multiplexing capability. Challenges and desired future perspectives for cost-effective, accurate, reliable, and multi-functions smartphone-based colorimetric tools have also been debated.

Metrological traceability in process analytical technologies and point-of-need technologies for food safety and quality control: not a straightforward issue

Traditional techniques for food analysis are based on off-line laboratory methods that are expensive and time-consuming and often require qualified personnel. Despite the high standards of accuracy and metrological traceability, these well-established methods do not facilitate real-time process monitoring and timely on-site decision-making as required for food safety and quality control. The future of food testing includes rapid, cost-effective, portable, and simple methods for both qualitative screening and quantification of food contaminants, as well as continuous, real-time measurement in production lines. Process automatization through process analytical technologies (PAT) is an increasing trend in the food industry as a way to achieve improved product quality, safety, and consistency, reduced production cycle times, minimal product waste or reworks, and the possibility for real-time product release. Novel methods of analysis for point-of-need (PON) screening could greatly improve food testing by allowing non-experts, such as consumers, to test in situ food products using portable instruments, smartphones, or even visual naked-eye inspections, or farmers and small producers to monitor products in the field. This requires the attention of the research community and devices manufacturers to ensure reliability of measurement results from PAT strategy and PON tests through the demonstration and critical evaluation of performance characteristics. The fitness for purpose of methods in real-life conditions is a priority that should not be overlooked in order to maintain an effective and harmonized food safety policy.

Colorimetry Combined with Inner Filter Effect-Based Fluorometry: A Versatile and Robust Strategy for Multimode Visualization of Food Dyes

Herein, a strategy combining colorimetry and inner filter effect (IFE)-based fluorometry was developed for multimode visualization of food dyes (FDs) using CdTe quantum-dots-doped fluorescent indicator papers as a sample-to-answer device. Colorimetry was straightforwardly achieved by FDs extraction through electrostatic interaction and hydrophobic effect while fluorometry was implemented by IFE-induced fluorescence quenching. RGB/gray-scale values of colorimetry and fluorometry were furtherly picked by a smartphone application and applied to reconstruct color information-based digital image analysis for both direct alignments and linear regression analysis. The apparent color and fluorescence of FDs-bound indicator papers, together with their digitized color information, showed a good mapping to FDs concentrations in the range of 0-0.5 mg/mL for Sunset Yellow, 0-0.2 mg/mL for Allura Red, and 0-0.08 mg/mL for Brilliant Blue. As a proof of concept, the dosages of these FDs in real beverages and simulated dye effluents were deduced and cross-validated by different visualization modes, and finally double-checked by instrumental techniques such as spectrometric methods, high-performance liquid chromatography (HPLC), and mass spectroscopy (MS). The above findings concluded that (i) IFE mechanism is generally applicable to build fluorometric systems and (ii) cross validation of different visualization modes can markedly improve detection accuracy, which may provide references for design and fabrication of novel "lab-on-paper" devices for visualization applications with high reliability.

Fluorescent Sensing of Ciprofloxacin and Chloramphenicol in Milk Samples via Inner Filter Effect and Photoinduced Electron Transfer Based on Nanosized Rod-Shaped Eu-MOF

Rapid, facile, and accurate detection of antibiotic residues is vital for practical applications. Herein, we designed a sensitive, visual, and rapid analytical method for sensitive detection of ciprofloxacin and chloramphenicol based on a nanosized rod-shaped Europium metal organic framework (Eu-MOF). The fluorescent Eu-MOF was firstly synthesized by a simple synthetic route at room temperature, which displays a red emission. The mechanisms of detecting ciprofloxacin and chloramphenicol were confirmed to be the inner filter effect (IFE) and photoinduced electron transfer (PET). Under the optimized experimental conditions, the detection limits of the developed method for ciprofloxacin and chloramphenicol detection were 0.0136 and 3.16 μM, respectively. Moreover, the sensor was effectively applied for quantitative determination of ciprofloxacin and chloramphenicol milk samples with satisfactory recoveries of 94.5-102% and 97-110%, respectively. This work developed a new method for rapid detection of ciprofloxacin and chloramphenicol residues. In addition, the established method has potential practical application value for on-site safety regulation on antibiotic residues in animal-derived food.

High-Efficiency Utilization of Waste Tobacco Stems to Synthesize Novel Biomass-Based Carbon Dots for Precise Detection of Tetracycline Antibiotic Residues

Recycling waste biomass into valuable products (e.g., nanomaterials) is of considerable theoretical and practical significance to achieve future sustainable development. Here, we propose a one-pot hydrothermal synthesis route to convert waste tobacco stems into biomass-based N, S-codoped carbon dots (C-dots) with the assistance of carbon black. Unlike most of the previously reported luminescent C-dots, these biomass-based C-dots showed a satisfactory stability, as well as an excitation-independent fluorescence emission at ~520 nm. Furthermore, they demonstrated a pH-dependent fluorescence emission ability, offering a scaffold to design pH-responsive assays. Moreover, these as-synthesized biomass-based C-dots exhibited a fluorescence response ability toward tetracycline antibiotics (TCs, e.g., TC, CTC, and OTC) through the inner filter effect (IFE), thereby allowing for the establishment a smart analytical platform to sensitively and selectively monitor residual TCs in real environmental water samples. In this study, we explored the conversion of waste tobacco stems into sustainable biomass-based C-dots to develop simple, efficient, label-free, reliable, low-cost, and eco-friendly analytical platforms for environmental pollution traceability analysis, which might provide a novel insight to resolve the ecological and environmental issues derived from waste tobacco stems.